Update upstream source from tag 'upstream/1.51.0'

Update to upstream version '1.51.0' with Debian dir 20ec082880941c65b5b91d008de1a402fcdf2fe1
author: Andrej Shadura <andrewsh@debian.org> 2022-01-25 17:19:30 +0100
committer: Andrej Shadura <andrewsh@debian.org> 2022-01-25 17:19:30 +0100
commit: a3314bc3fb01a561884a7f1cfe8cb8161e582655 (patch)
tree: ad313f9f848e964d9028260931dcf64177c23ec0
parent: 0e0f67024b1d67178e063ffd2a86cfb78ab1e08a (diff)
parent: 0027c02b907486b437772b1cdecbea14d18597d9 (diff)
134 files changed, 2565 insertions, 1646 deletions
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index 6c3a9984..0dfab4e0 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -8,6 +8,7 @@
   - Use markdown where necessary, mostly for `code blocks`.
   - End with either a period (.) or an exclamation mark (!).
   - Start with a capital letter.
+  - Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
 * [ ] Pull request includes a [sign off](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#sign-off)
 * [ ] [Code style](https://matrix-org.github.io/synapse/latest/code_style.html) is correct
   (run the [linters](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index cb72e1a2..4f580697 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -366,6 +366,8 @@ jobs:
       # Build initial Synapse image
       - run: docker build -t matrixdotorg/synapse:latest -f docker/Dockerfile .
         working-directory: synapse
+        env:
+          DOCKER_BUILDKIT: 1
 
       # Build a ready-to-run Synapse image based on the initial image above.
       # This new image includes a config file, keys for signing and TLS, and
@@ -374,7 +376,8 @@ jobs:
         working-directory: complement/dockerfiles
 
       # Run Complement
-      - run: go test -v -tags synapse_blacklist,msc2403 ./tests/...
+      - run: set -o pipefail && go test -v -json -tags synapse_blacklist,msc2403 ./tests/... 2>&1 | gotestfmt
+        shell: bash
         env:
           COMPLEMENT_BASE_IMAGE: complement-synapse:latest
         working-directory: complement
diff --git a/.gitignore b/.gitignore
index fe137f33..3bd6b1a0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,3 +50,7 @@ __pycache__/
 
 # docs
 book/
+
+# complement
+/complement-*
+/master.tar.gz
diff --git a/CHANGES.md b/CHANGES.md
index b8f3588e..d3dcd0ed 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,12 +1,94 @@
-Synapse 1.50.2 (2022-01-24)
+Synapse 1.51.0 (2022-01-25)
 ===========================
 
+No significant changes since 1.51.0rc2.
+
+Synapse 1.51.0 deprecates `webclient` listeners and non-HTTP(S) `web_client_location`s. Support for these will be removed in Synapse 1.53.0, at which point Synapse will not be capable of directly serving a web client for Matrix.
+
+Synapse 1.51.0rc2 (2022-01-24)
+==============================
+
 Bugfixes
 --------
 
 - Fix a bug introduced in Synapse 1.40.0 that caused Synapse to fail to process incoming federation traffic after handling a large amount of events in a v1 room. ([\#11806](https://github.com/matrix-org/synapse/issues/11806))
 
 
+Synapse 1.51.0rc1 (2022-01-21)
+==============================
+
+Features
+--------
+
+- Add `track_puppeted_user_ips` config flag to record client IP addresses against puppeted users, and include the puppeted users in monthly active user counts. ([\#11561](https://github.com/matrix-org/synapse/issues/11561), [\#11749](https://github.com/matrix-org/synapse/issues/11749), [\#11757](https://github.com/matrix-org/synapse/issues/11757))
+- Include whether the requesting user has participated in a thread when generating a summary for [MSC3440](https://github.com/matrix-org/matrix-doc/pull/3440). ([\#11577](https://github.com/matrix-org/synapse/issues/11577))
+- Return an `M_FORBIDDEN` error code instead of `M_UNKNOWN` when a spam checker module prevents a user from creating a room. ([\#11672](https://github.com/matrix-org/synapse/issues/11672))
+- Add a flag to the `synapse_review_recent_signups` script to ignore and filter appservice users. ([\#11675](https://github.com/matrix-org/synapse/issues/11675), [\#11770](https://github.com/matrix-org/synapse/issues/11770))
+
+
+Bugfixes
+--------
+
+- Fix a long-standing issue which could cause Synapse to incorrectly accept data in the unsigned field of events
+  received over federation. ([\#11530](https://github.com/matrix-org/synapse/issues/11530))
+- Fix a long-standing bug where Synapse wouldn't cache a response indicating that a remote user has no devices. ([\#11587](https://github.com/matrix-org/synapse/issues/11587))
+- Fix an error that occurs whilst trying to get the federation status of a destination server that was working normally. This admin API was newly introduced in Synapse v1.49.0. ([\#11593](https://github.com/matrix-org/synapse/issues/11593))
+- Fix bundled aggregations not being included in the `/sync` response, per [MSC2675](https://github.com/matrix-org/matrix-doc/pull/2675). ([\#11612](https://github.com/matrix-org/synapse/issues/11612), [\#11659](https://github.com/matrix-org/synapse/issues/11659), [\#11791](https://github.com/matrix-org/synapse/issues/11791))
+- Fix the `/_matrix/client/v1/room/{roomId}/hierarchy` endpoint returning incorrect fields which have been present since Synapse 1.49.0. ([\#11667](https://github.com/matrix-org/synapse/issues/11667))
+- Fix preview of some GIF URLs (like tenor.com). Contributed by Philippe Daouadi. ([\#11669](https://github.com/matrix-org/synapse/issues/11669))
+- Fix a bug where only the first 50 rooms from a space were returned from the `/hierarchy` API. This has existed since the introduction of the API in Synapse v1.41.0. ([\#11695](https://github.com/matrix-org/synapse/issues/11695))
+- Fix a bug introduced in Synapse v1.18.0 where password reset and address validation emails would not be sent if their subject was configured to use the 'app' template variable. Contributed by @br4nnigan. ([\#11710](https://github.com/matrix-org/synapse/issues/11710), [\#11745](https://github.com/matrix-org/synapse/issues/11745))
+- Make the 'List Rooms' Admin API sort stable. Contributed by Daniël Sonck. ([\#11737](https://github.com/matrix-org/synapse/issues/11737))
+- Fix a long-standing bug where space hierarchy over federation would only work correctly some of the time. ([\#11775](https://github.com/matrix-org/synapse/issues/11775))
+- Fix a bug introduced in Synapse v1.46.0 that prevented `on_logged_out` module callbacks from being correctly awaited by Synapse. ([\#11786](https://github.com/matrix-org/synapse/issues/11786))
+
+
+Improved Documentation
+----------------------
+
+- Warn against using a Let's Encrypt certificate for TLS/DTLS TURN server client connections, and suggest using ZeroSSL certificate instead. This works around client-side connectivity errors caused by WebRTC libraries that reject Let's Encrypt certificates. Contibuted by @AndrewFerr. ([\#11686](https://github.com/matrix-org/synapse/issues/11686))
+- Document the new `SYNAPSE_TEST_PERSIST_SQLITE_DB` environment variable in the contributing guide. ([\#11715](https://github.com/matrix-org/synapse/issues/11715))
+- Document that the minimum supported PostgreSQL version is now 10. ([\#11725](https://github.com/matrix-org/synapse/issues/11725))
+- Fix typo in demo docs: differnt. ([\#11735](https://github.com/matrix-org/synapse/issues/11735))
+- Update room spec URL in config files. ([\#11739](https://github.com/matrix-org/synapse/issues/11739))
+- Mention `python3-venv` and `libpq-dev` dependencies in the contribution guide. ([\#11740](https://github.com/matrix-org/synapse/issues/11740))
+- Update documentation for configuring login with Facebook. ([\#11755](https://github.com/matrix-org/synapse/issues/11755))
+- Update installation instructions to note that Python 3.6 is no longer supported. ([\#11781](https://github.com/matrix-org/synapse/issues/11781))
+
+
+Deprecations and Removals
+-------------------------
+
+- Remove the unstable `/send_relation` endpoint. ([\#11682](https://github.com/matrix-org/synapse/issues/11682))
+- Remove `python_twisted_reactor_pending_calls` Prometheus metric. ([\#11724](https://github.com/matrix-org/synapse/issues/11724))
+- Remove the `password_hash` field from the response dictionaries of the [Users Admin API](https://matrix-org.github.io/synapse/latest/admin_api/user_admin_api.html). ([\#11576](https://github.com/matrix-org/synapse/issues/11576))
+- **Deprecate support for `webclient` listeners and non-HTTP(S) `web_client_location` configuration. ([\#11774](https://github.com/matrix-org/synapse/issues/11774), [\#11783](https://github.com/matrix-org/synapse/issues/11783))**
+
+
+Internal Changes
+----------------
+
+- Run `pyupgrade --py37-plus --keep-percent-format` on Synapse. ([\#11685](https://github.com/matrix-org/synapse/issues/11685))
+- Use buildkit's cache feature to speed up docker builds. ([\#11691](https://github.com/matrix-org/synapse/issues/11691))
+- Use `auto_attribs` and native type hints for attrs classes. ([\#11692](https://github.com/matrix-org/synapse/issues/11692), [\#11768](https://github.com/matrix-org/synapse/issues/11768))
+- Remove debug logging for #4422, which has been closed since Synapse 0.99. ([\#11693](https://github.com/matrix-org/synapse/issues/11693))
+- Remove fallback code for Python 2. ([\#11699](https://github.com/matrix-org/synapse/issues/11699))
+- Add a test for [an edge case](https://github.com/matrix-org/synapse/pull/11532#discussion_r769104461) in the `/sync` logic. ([\#11701](https://github.com/matrix-org/synapse/issues/11701))
+- Add the option to write SQLite test dbs to disk when running tests. ([\#11702](https://github.com/matrix-org/synapse/issues/11702))
+- Improve Complement test output for Gitub Actions. ([\#11707](https://github.com/matrix-org/synapse/issues/11707))
+- Fix docstring on `add_account_data_for_user`. ([\#11716](https://github.com/matrix-org/synapse/issues/11716))
+- Complement environment variable name change and update `.gitignore`. ([\#11718](https://github.com/matrix-org/synapse/issues/11718))
+- Simplify calculation of Prometheus metrics for garbage collection. ([\#11723](https://github.com/matrix-org/synapse/issues/11723))
+- Improve accuracy of `python_twisted_reactor_tick_time` Prometheus metric. ([\#11724](https://github.com/matrix-org/synapse/issues/11724), [\#11771](https://github.com/matrix-org/synapse/issues/11771))
+- Minor efficiency improvements when inserting many values into the database. ([\#11742](https://github.com/matrix-org/synapse/issues/11742))
+- Invite PR authors to give themselves credit in the changelog. ([\#11744](https://github.com/matrix-org/synapse/issues/11744))
+- Add optional debugging to investigate [issue 8631](https://github.com/matrix-org/synapse/issues/8631). ([\#11760](https://github.com/matrix-org/synapse/issues/11760))
+- Remove `log_function` utility function and its uses. ([\#11761](https://github.com/matrix-org/synapse/issues/11761))
+- Add a unit test that checks both `client` and `webclient` resources will function when simultaneously enabled. ([\#11765](https://github.com/matrix-org/synapse/issues/11765))
+- Allow overriding complement commit using `COMPLEMENT_REF`. ([\#11766](https://github.com/matrix-org/synapse/issues/11766))
+- Add some comments and type annotations for `_update_outliers_txn`. ([\#11776](https://github.com/matrix-org/synapse/issues/11776))
+
+
 Synapse 1.50.1 (2022-01-18)
 ===========================
 
diff --git a/contrib/prometheus/consoles/synapse.html b/contrib/prometheus/consoles/synapse.html
index cd9ad152..d17c8a08 100644
--- a/contrib/prometheus/consoles/synapse.html
+++ b/contrib/prometheus/consoles/synapse.html
@@ -92,22 +92,6 @@ new PromConsole.Graph({
 })
 </script>
 
-<h3>Pending calls per tick</h3>
-<div id="reactor_pending_calls"></div>
-<script>
-new PromConsole.Graph({
-  node: document.querySelector("#reactor_pending_calls"),
-  expr: "rate(python_twisted_reactor_pending_calls_sum[30s]) / rate(python_twisted_reactor_pending_calls_count[30s])",
-  name: "[[job]]-[[index]]",
-  min: 0,
-  renderer: "line",
-  height: 150,
-  yAxisFormatter: PromConsole.NumberFormatter.humanize,
-  yHoverFormatter: PromConsole.NumberFormatter.humanize,
-  yTitle: "Pending Calls"
-})
-</script>
-
 <h1>Storage</h1>
 
 <h3>Queries</h3>
diff --git a/demo/README b/demo/README
index 0bec820a..a5a95bd1 100644
--- a/demo/README
+++ b/demo/README
@@ -22,5 +22,5 @@ Logs and sqlitedb will be stored in demo/808{0,1,2}.{log,db}
 
 
 
-Also note that when joining a public room on a differnt HS via "#foo:bar.net", then you are (in the current impl) joining a room with room_id "foo". This means that it won't work if your HS already has a room with that name.
+Also note that when joining a public room on a different HS via "#foo:bar.net", then you are (in the current impl) joining a room with room_id "foo". This means that it won't work if your HS already has a room with that name.
 
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 2bdc607e..306f75ae 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,14 +1,17 @@
 # Dockerfile to build the matrixdotorg/synapse docker images.
 #
+# Note that it uses features which are only available in BuildKit - see
+# https://docs.docker.com/go/buildkit/ for more information.
+#
 # To build the image, run `docker build` command from the root of the
 # synapse repository:
 #
-#    docker build -f docker/Dockerfile .
+#    DOCKER_BUILDKIT=1 docker build -f docker/Dockerfile .
 #
 # There is an optional PYTHON_VERSION build argument which sets the
 # version of python to build against: for example:
 #
-#    docker build -f docker/Dockerfile --build-arg PYTHON_VERSION=3.6 .
+#    DOCKER_BUILDKIT=1 docker build -f docker/Dockerfile --build-arg PYTHON_VERSION=3.9 .
 #
 
 ARG PYTHON_VERSION=3.8
@@ -19,7 +22,16 @@ ARG PYTHON_VERSION=3.8
 FROM docker.io/python:${PYTHON_VERSION}-slim as builder
 
 # install the OS build deps
-RUN apt-get update && apt-get install -y \
+#
+# RUN --mount is specific to buildkit and is documented at
+# https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/syntax.md#build-mounts-run---mount.
+# Here we use it to set up a cache for apt, to improve rebuild speeds on
+# slow connections.
+#
+RUN \
+   --mount=type=cache,target=/var/cache/apt,sharing=locked \
+   --mount=type=cache,target=/var/lib/apt,sharing=locked \
+ apt-get update && apt-get install -y \
     build-essential \
     libffi-dev \
     libjpeg-dev \
@@ -44,7 +56,8 @@ COPY synapse/python_dependencies.py /synapse/synapse/python_dependencies.py
 # used while you develop on the source
 #
 # This is aiming at installing the `install_requires` and `extras_require` from `setup.py`
-RUN pip install --prefix="/install" --no-warn-script-location \
+RUN --mount=type=cache,target=/root/.cache/pip \
+  pip install --prefix="/install" --no-warn-script-location \
     /synapse[all]
 
 # Copy over the rest of the project
@@ -66,7 +79,10 @@ LABEL org.opencontainers.image.documentation='https://github.com/matrix-org/syna
 LABEL org.opencontainers.image.source='https://github.com/matrix-org/synapse.git'
 LABEL org.opencontainers.image.licenses='Apache-2.0'
 
-RUN apt-get update && apt-get install -y \
+RUN \
+   --mount=type=cache,target=/var/cache/apt,sharing=locked \
+   --mount=type=cache,target=/var/lib/apt,sharing=locked \
+  apt-get update && apt-get install -y \
     curl \
     gosu \
     libjpeg62-turbo \
diff --git a/docs/admin_api/user_admin_api.md b/docs/admin_api/user_admin_api.md
index 74933d2f..c514cadb 100644
--- a/docs/admin_api/user_admin_api.md
+++ b/docs/admin_api/user_admin_api.md
@@ -15,9 +15,10 @@ server admin: [Admin API](../usage/administration/admin_api)
 
 It returns a JSON body like the following:
 
-```json
+```jsonc
 {
-    "displayname": "User",
+    "name": "@user:example.com",
+    "displayname": "User", // can be null if not set
     "threepids": [
         {
             "medium": "email",
@@ -32,11 +33,11 @@ It returns a JSON body like the following:
             "validated_at": 1586458409743
         }
     ],
-    "avatar_url": "<avatar_url>",
+    "avatar_url": "<avatar_url>",  // can be null if not set
+    "is_guest": 0,
     "admin": 0,
     "deactivated": 0,
     "shadow_banned": 0,
-    "password_hash": "$2b$12$p9B4GkqYdRTPGD",
     "creation_ts": 1560432506,
     "appservice_id": null,
     "consent_server_notice_sent": null,
diff --git a/docs/development/contributing_guide.md b/docs/development/contributing_guide.md
index abdb8084..c1429816 100644
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -20,7 +20,9 @@ recommended for development. More information about WSL can be found at
 <https://docs.microsoft.com/en-us/windows/wsl/install>. Running Synapse natively
 on Windows is not officially supported.
 
-The code of Synapse is written in Python 3. To do pretty much anything, you'll need [a recent version of Python 3](https://wiki.python.org/moin/BeginnersGuide/Download).
+The code of Synapse is written in Python 3. To do pretty much anything, you'll need [a recent version of Python 3](https://www.python.org/downloads/). Your Python also needs support for [virtual environments](https://docs.python.org/3/library/venv.html). This is usually built-in, but some Linux distributions like Debian and Ubuntu split it out into its own package. Running `sudo apt install python3-venv` should be enough.
+
+Synapse can connect to PostgreSQL via the [psycopg2](https://pypi.org/project/psycopg2/) Python library. Building this library from source requires access to PostgreSQL's C header files. On Debian or Ubuntu Linux, these can be installed with `sudo apt install libpq-dev`.
 
 The source code of Synapse is hosted on GitHub. You will also need [a recent version of git](https://github.com/git-guides/install-git).
 
@@ -169,6 +171,27 @@ To increase the log level for the tests, set `SYNAPSE_TEST_LOG_LEVEL`:
 SYNAPSE_TEST_LOG_LEVEL=DEBUG trial tests
 ```
 
+By default, tests will use an in-memory SQLite database for test data. For additional
+help with debugging, one can use an on-disk SQLite database file instead, in order to
+review database state during and after running tests. This can be done by setting
+the `SYNAPSE_TEST_PERSIST_SQLITE_DB` environment variable. Doing so will cause the
+database state to be stored in a file named `test.db` under the trial process'
+working directory. Typically, this ends up being `_trial_temp/test.db`. For example:
+
+```sh
+SYNAPSE_TEST_PERSIST_SQLITE_DB=1 trial tests
+```
+
+The database file can then be inspected with:
+
+```sh
+sqlite3 _trial_temp/test.db
+```
+
+Note that the database file is cleared at the beginning of each test run. Thus it 
+will always only contain the data generated by the *last run test*. Though generally
+when debugging, one is only running a single test anyway.
+
 ### Running tests under PostgreSQL
 
 Invoking `trial` as above will use an in-memory SQLite database. This is great for
diff --git a/docs/development/url_previews.md b/docs/development/url_previews.md
index aff38136..154b9a5e 100644
--- a/docs/development/url_previews.md
+++ b/docs/development/url_previews.md
@@ -35,7 +35,12 @@ When Synapse is asked to preview a URL it does the following:
    5. If the media is HTML:
       1. Decodes the HTML via the stored file.
       2. Generates an Open Graph response from the HTML.
-      3. If an image exists in the Open Graph response:
+      3. If a JSON oEmbed URL was found in the HTML via autodiscovery:
+         1. Downloads the URL and stores it into a file via the media storage provider
+            and saves the local media metadata.
+         2. Convert the oEmbed response to an Open Graph response.
+         3. Override any Open Graph data from the HTML with data from oEmbed.
+      4. If an image exists in the Open Graph response:
          1. Downloads the URL and stores it into a file via the media storage
             provider and saves the local media metadata.
          2. Generates thumbnails.
diff --git a/docs/openid.md b/docs/openid.md
index ff9de9d5..171ea3b7 100644
--- a/docs/openid.md
+++ b/docs/openid.md
@@ -390,9 +390,6 @@ oidc_providers:
 
 ### Facebook
 
-Like Github, Facebook provide a custom OAuth2 API rather than an OIDC-compliant
-one so requires a little more configuration.
-
 0. You will need a Facebook developer account. You can register for one
    [here](https://developers.facebook.com/async/registration/).
 1. On the [apps](https://developers.facebook.com/apps/) page of the developer
@@ -412,24 +409,28 @@ Synapse config:
     idp_name: Facebook
     idp_brand: "facebook"  # optional: styling hint for clients
     discover: false
-    issuer: "https://facebook.com"
+    issuer: "https://www.facebook.com"
     client_id: "your-client-id" # TO BE FILLED
     client_secret: "your-client-secret" # TO BE FILLED
     scopes: ["openid", "email"]
-    authorization_endpoint: https://facebook.com/dialog/oauth
-    token_endpoint: https://graph.facebook.com/v9.0/oauth/access_token
-    user_profile_method: "userinfo_endpoint"
-    userinfo_endpoint: "https://graph.facebook.com/v9.0/me?fields=id,name,email,picture"
+    authorization_endpoint: "https://facebook.com/dialog/oauth"
+    token_endpoint: "https://graph.facebook.com/v9.0/oauth/access_token"
+    jwks_uri: "https://www.facebook.com/.well-known/oauth/openid/jwks/"
     user_mapping_provider:
       config:
-        subject_claim: "id"
         display_name_template: "{{ user.name }}"
+        email_template: "{{ '{{ user.email }}' }}"
 ```
 
 Relevant documents:
- * https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow
- * Using Facebook's Graph API: https://developers.facebook.com/docs/graph-api/using-graph-api/
- * Reference to the User endpoint: https://developers.facebook.com/docs/graph-api/reference/user
+ * [Manually Build a Login Flow](https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow)
+ * [Using Facebook's Graph API](https://developers.facebook.com/docs/graph-api/using-graph-api/)
+ * [Reference to the User endpoint](https://developers.facebook.com/docs/graph-api/reference/user)
+
+Facebook do have an [OIDC discovery endpoint](https://www.facebook.com/.well-known/openid-configuration),
+but it has a `response_types_supported` which excludes "code" (which we rely on, and
+is even mentioned in their [documentation](https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow#login)),
+so we have to disable discovery and configure the URIs manually.
 
 ### Gitea
 
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index 810a14b0..1b86d029 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -74,13 +74,7 @@ server_name: "SERVERNAME"
 #
 pid_file: DATADIR/homeserver.pid
 
-# The absolute URL to the web client which /_matrix/client will redirect
-# to if 'webclient' is configured under the 'listeners' configuration.
-#
-# This option can be also set to the filesystem path to the web client
-# which will be served at /_matrix/client/ if 'webclient' is configured
-# under the 'listeners' configuration, however this is a security risk:
-# https://github.com/matrix-org/synapse#security-note
+# The absolute URL to the web client which / will redirect to.
 #
 #web_client_location: https://riot.example.com/
 
@@ -164,7 +158,7 @@ presence:
 # The default room version for newly created rooms.
 #
 # Known room versions are listed here:
-# https://matrix.org/docs/spec/#complete-list-of-room-versions
+# https://spec.matrix.org/latest/rooms/#complete-list-of-room-versions
 #
 # For example, for room version 1, default_room_version should be set
 # to "1".
@@ -310,8 +304,6 @@ presence:
 #   static: static resources under synapse/static (/_matrix/static). (Mostly
 #       useful for 'fallback authentication'.)
 #
-#   webclient: A web client. Requires web_client_location to be set.
-#
 listeners:
   # TLS-enabled listener: for when matrix traffic is sent directly to synapse.
   #
@@ -1503,6 +1495,21 @@ room_prejoin_state:
    #additional_event_types:
    #  - org.example.custom.event.type
 
+# We record the IP address of clients used to access the API for various
+# reasons, including displaying it to the user in the "Where you're signed in"
+# dialog.
+#
+# By default, when puppeting another user via the admin API, the client IP
+# address is recorded against the user who created the access token (ie, the
+# admin user), and *not* the puppeted user.
+#
+# Uncomment the following to also record the IP address against the puppeted
+# user. (This also means that the puppeted user will count as an "active" user
+# for the purpose of monthly active user tracking - see 'limit_usage_by_mau' etc
+# above.)
+#
+#track_puppeted_user_ips: true
+
 
 # A list of application service config files to use
 #
@@ -1870,10 +1877,13 @@ saml2_config:
 #       Defaults to false. Avoid this in production.
 #
 #   user_profile_method: Whether to fetch the user profile from the userinfo
-#       endpoint. Valid values are: 'auto' or 'userinfo_endpoint'.
+#       endpoint, or to rely on the data returned in the id_token from the
+#       token_endpoint.
+#
+#       Valid values are: 'auto' or 'userinfo_endpoint'.
 #
-#       Defaults to 'auto', which fetches the userinfo endpoint if 'openid' is
-#       included in 'scopes'. Set to 'userinfo_endpoint' to always fetch the
+#       Defaults to 'auto', which uses the userinfo endpoint if 'openid' is
+#       not included in 'scopes'. Set to 'userinfo_endpoint' to always use the
 #       userinfo endpoint.
 #
 #   allow_existing_users: set to 'true' to allow a user logging in via OIDC to
diff --git a/docs/setup/installation.md b/docs/setup/installation.md
index 210c80da..fe657a15 100644
--- a/docs/setup/installation.md
+++ b/docs/setup/installation.md
@@ -194,7 +194,7 @@ When following this route please make sure that the [Platform-specific prerequis
 System requirements:
 
 - POSIX-compliant system (tested on Linux & OS X)
-- Python 3.6 or later, up to Python 3.9.
+- Python 3.7 or later, up to Python 3.9.
 - At least 1GB of free RAM if you want to join large public rooms like #matrix:matrix.org
 
 To install the Synapse homeserver run:
diff --git a/docs/turn-howto.md b/docs/turn-howto.md
index e32aaa18..eba7ca61 100644
--- a/docs/turn-howto.md
+++ b/docs/turn-howto.md
@@ -137,6 +137,10 @@ This will install and start a systemd service called `coturn`.
 
     # TLS private key file
     pkey=/path/to/privkey.pem
+
+    # Ensure the configuration lines that disable TLS/DTLS are commented-out or removed
+    #no-tls
+    #no-dtls
     ```
 
     In this case, replace the `turn:` schemes in the `turn_uris` settings below
@@ -145,6 +149,14 @@ This will install and start a systemd service called `coturn`.
     We recommend that you only try to set up TLS/DTLS once you have set up a
     basic installation and got it working.
 
+    NB: If your TLS certificate was provided by Let's Encrypt, TLS/DTLS will
+    not work with any Matrix client that uses Chromium's WebRTC library. This
+    currently includes Element Android & iOS; for more details, see their
+    [respective](https://github.com/vector-im/element-android/issues/1533)
+    [issues](https://github.com/vector-im/element-ios/issues/2712) as well as the underlying
+    [WebRTC issue](https://bugs.chromium.org/p/webrtc/issues/detail?id=11710).
+    Consider using a ZeroSSL certificate for your TURN server as a working alternative.
+
 1.  Ensure your firewall allows traffic into the TURN server on the ports
     you've configured it to listen on (By default: 3478 and 5349 for TURN
     traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
@@ -250,6 +262,10 @@ Here are a few things to try:
  * Check that you have opened your firewall to allow UDP traffic to the UDP
    relay ports (49152-65535 by default).
 
+ * Try disabling `coturn`'s TLS/DTLS listeners and enable only its (unencrypted)
+   TCP/UDP listeners. (This will only leave signaling traffic unencrypted;
+   voice & video WebRTC traffic is always encrypted.)
+
  * Some WebRTC implementations (notably, that of Google Chrome) appear to get
    confused by TURN servers which are reachable over IPv6 (this appears to be
    an unexpected side-effect of its handling of multiple IP addresses as
diff --git a/docs/upgrade.md b/docs/upgrade.md
index 30bb0dcd..f455d257 100644
--- a/docs/upgrade.md
+++ b/docs/upgrade.md
@@ -85,6 +85,17 @@ process, for example:
     dpkg -i matrix-synapse-py3_1.3.0+stretch1_amd64.deb
     ```
 
+# Upgrading to v1.51.0
+
+## Deprecation of `webclient` listeners and non-HTTP(S) `web_client_location`
+
+Listeners of type  `webclient` are deprecated and scheduled to be removed in
+Synapse v1.53.0.
+
+Similarly, a non-HTTP(S) `web_client_location` configuration is deprecated and
+will become a configuration error in Synapse v1.53.0.
+
+
 # Upgrading to v1.50.0
 
 ## Dropping support for old Python and Postgres versions
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
index 53295b58..e08ffeda 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -8,7 +8,8 @@
 # By default the script will fetch the latest Complement master branch and
 # run tests with that. This can be overridden to use a custom Complement
 # checkout by setting the COMPLEMENT_DIR environment variable to the
-# filepath of a local Complement checkout.
+# filepath of a local Complement checkout or by setting the COMPLEMENT_REF
+# environment variable to pull a different branch or commit.
 #
 # By default Synapse is run in monolith mode. This can be overridden by
 # setting the WORKERS environment variable.
@@ -23,16 +24,20 @@
 # Exit if a line returns a non-zero exit code
 set -e
 
+# enable buildkit for the docker builds
+export DOCKER_BUILDKIT=1
+
 # Change to the repository root
 cd "$(dirname $0)/.."
 
 # Check for a user-specified Complement checkout
 if [[ -z "$COMPLEMENT_DIR" ]]; then
-  echo "COMPLEMENT_DIR not set. Fetching the latest Complement checkout..."
-  wget -Nq https://github.com/matrix-org/complement/archive/master.tar.gz
-  tar -xzf master.tar.gz
-  COMPLEMENT_DIR=complement-master
-  echo "Checkout available at 'complement-master'"
+  COMPLEMENT_REF=${COMPLEMENT_REF:-master}
+  echo "COMPLEMENT_DIR not set. Fetching Complement checkout from ${COMPLEMENT_REF}..."
+  wget -Nq https://github.com/matrix-org/complement/archive/${COMPLEMENT_REF}.tar.gz
+  tar -xzf ${COMPLEMENT_REF}.tar.gz
+  COMPLEMENT_DIR=complement-${COMPLEMENT_REF}
+  echo "Checkout available at 'complement-${COMPLEMENT_REF}'"
 fi
 
 # Build the base Synapse image from the local checkout
@@ -47,7 +52,7 @@ if [[ -n "$WORKERS" ]]; then
   COMPLEMENT_DOCKERFILE=SynapseWorkers.Dockerfile
   # And provide some more configuration to complement.
   export COMPLEMENT_CA=true
-  export COMPLEMENT_VERSION_CHECK_ITERATIONS=500
+  export COMPLEMENT_SPAWN_HS_TIMEOUT_SECS=25
 else
   export COMPLEMENT_BASE_IMAGE=complement-synapse
   COMPLEMENT_DOCKERFILE=Synapse.Dockerfile
@@ -65,4 +70,5 @@ if [[ -n "$1" ]]; then
 fi
 
 # Run the tests!
+echo "Images built; running complement"
 go test -v -tags synapse_blacklist,msc2403 -count=1 $EXTRA_COMPLEMENT_ARGS ./tests/...
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 5ef294cd..26bdfec3 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -47,7 +47,7 @@ try:
 except ImportError:
     pass
 
-__version__ = "1.50.2"
+__version__ = "1.51.0"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when
diff --git a/synapse/_scripts/review_recent_signups.py b/synapse/_scripts/review_recent_signups.py
index 093af432..e207f154 100644
--- a/synapse/_scripts/review_recent_signups.py
+++ b/synapse/_scripts/review_recent_signups.py
@@ -46,7 +46,9 @@ class UserInfo:
     ips: List[str] = attr.Factory(list)
 
 
-def get_recent_users(txn: LoggingTransaction, since_ms: int) -> List[UserInfo]:
+def get_recent_users(
+    txn: LoggingTransaction, since_ms: int, exclude_app_service: bool
+) -> List[UserInfo]:
     """Fetches recently registered users and some info on them."""
 
     sql = """
@@ -56,6 +58,9 @@ def get_recent_users(txn: LoggingTransaction, since_ms: int) -> List[UserInfo]:
             AND deactivated = 0
     """
 
+    if exclude_app_service:
+        sql += " AND appservice_id IS NULL"
+
     txn.execute(sql, (since_ms / 1000,))
 
     user_infos = [UserInfo(user_id, creation_ts) for user_id, creation_ts in txn]
@@ -113,7 +118,7 @@ def main() -> None:
         "-e",
         "--exclude-emails",
         action="store_true",
-        help="Exclude users that have validated email addresses",
+        help="Exclude users that have validated email addresses.",
     )
     parser.add_argument(
         "-u",
@@ -121,6 +126,12 @@ def main() -> None:
         action="store_true",
         help="Only print user IDs that match.",
     )
+    parser.add_argument(
+        "-a",
+        "--exclude-app-service",
+        help="Exclude appservice users.",
+        action="store_true",
+    )
 
     config = ReviewConfig()
 
@@ -133,6 +144,7 @@ def main() -> None:
 
     since_ms = time.time() * 1000 - Config.parse_duration(config_args.since)
     exclude_users_with_email = config_args.exclude_emails
+    exclude_users_with_appservice = config_args.exclude_app_service
     include_context = not config_args.only_users
 
     for database_config in config.database.databases:
@@ -143,7 +155,7 @@ def main() -> None:
 
     with make_conn(database_config, engine, "review_recent_signups") as db_conn:
         # This generates a type of Cursor, not LoggingTransaction.
-        user_infos = get_recent_users(db_conn.cursor(), since_ms)  # type: ignore[arg-type]
+        user_infos = get_recent_users(db_conn.cursor(), since_ms, exclude_users_with_appservice)  # type: ignore[arg-type]
 
     for user_info in user_infos:
         if exclude_users_with_email and user_info.emails:
diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index 4a32d430..68324120 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -71,6 +71,7 @@ class Auth:
         self._auth_blocking = AuthBlocking(self.hs)
 
         self._track_appservice_user_ips = hs.config.appservice.track_appservice_user_ips
+        self._track_puppeted_user_ips = hs.config.api.track_puppeted_user_ips
         self._macaroon_secret_key = hs.config.key.macaroon_secret_key
         self._force_tracing_for_users = hs.config.tracing.force_tracing_for_users
 
@@ -246,6 +247,18 @@ class Auth:
                     user_agent=user_agent,
                     device_id=device_id,
                 )
+                # Track also the puppeted user client IP if enabled and the user is puppeting
+                if (
+                    user_info.user_id != user_info.token_owner
+                    and self._track_puppeted_user_ips
+                ):
+                    await self.store.insert_client_ip(
+                        user_id=user_info.user_id,
+                        access_token=access_token,
+                        ip=ip_addr,
+                        user_agent=user_agent,
+                        device_id=device_id,
+                    )
 
             if is_guest and not allow_guest:
                 raise AuthError(
diff --git a/synapse/api/room_versions.py b/synapse/api/room_versions.py
index 0a895bba..a747a408 100644
--- a/synapse/api/room_versions.py
+++ b/synapse/api/room_versions.py
@@ -46,41 +46,41 @@ class RoomDisposition:
     UNSTABLE = "unstable"
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class RoomVersion:
     """An object which describes the unique attributes of a room version."""
 
-    identifier = attr.ib(type=str)  # the identifier for this version
-    disposition = attr.ib(type=str)  # one of the RoomDispositions
-    event_format = attr.ib(type=int)  # one of the EventFormatVersions
-    state_res = attr.ib(type=int)  # one of the StateResolutionVersions
-    enforce_key_validity = attr.ib(type=bool)
+    identifier: str  # the identifier for this version
+    disposition: str  # one of the RoomDispositions
+    event_format: int  # one of the EventFormatVersions
+    state_res: int  # one of the StateResolutionVersions
+    enforce_key_validity: bool
 
     # Before MSC2432, m.room.aliases had special auth rules and redaction rules
-    special_case_aliases_auth = attr.ib(type=bool)
+    special_case_aliases_auth: bool
     # Strictly enforce canonicaljson, do not allow:
     # * Integers outside the range of [-2 ^ 53 + 1, 2 ^ 53 - 1]
     # * Floats
     # * NaN, Infinity, -Infinity
-    strict_canonicaljson = attr.ib(type=bool)
+    strict_canonicaljson: bool
     # MSC2209: Check 'notifications' key while verifying
     # m.room.power_levels auth rules.
-    limit_notifications_power_levels = attr.ib(type=bool)
+    limit_notifications_power_levels: bool
     # MSC2174/MSC2176: Apply updated redaction rules algorithm.
-    msc2176_redaction_rules = attr.ib(type=bool)
+    msc2176_redaction_rules: bool
     # MSC3083: Support the 'restricted' join_rule.
-    msc3083_join_rules = attr.ib(type=bool)
+    msc3083_join_rules: bool
     # MSC3375: Support for the proper redaction rules for MSC3083. This mustn't
     #          be enabled if MSC3083 is not.
-    msc3375_redaction_rules = attr.ib(type=bool)
+    msc3375_redaction_rules: bool
     # MSC2403: Allows join_rules to be set to 'knock', changes auth rules to allow sending
     # m.room.membership event with membership 'knock'.
-    msc2403_knocking = attr.ib(type=bool)
+    msc2403_knocking: bool
     # MSC2716: Adds m.room.power_levels -> content.historical field to control
     # whether "insertion", "chunk", "marker" events can be sent
-    msc2716_historical = attr.ib(type=bool)
+    msc2716_historical: bool
     # MSC2716: Adds support for redacting "insertion", "chunk", and "marker" events
-    msc2716_redactions = attr.ib(type=bool)
+    msc2716_redactions: bool
 
 
 class RoomVersions:
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 5fc59c1b..579adbbc 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -60,7 +60,7 @@ from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
 from synapse.handlers.auth import load_legacy_password_auth_providers
 from synapse.logging.context import PreserveLoggingContext
-from synapse.metrics import register_threadpool
+from synapse.metrics import install_gc_manager, register_threadpool
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.metrics.jemalloc import setup_jemalloc_stats
 from synapse.types import ISynapseReactor
@@ -159,6 +159,7 @@ def start_reactor(
         change_resource_limit(soft_file_limit)
         if gc_thresholds:
             gc.set_threshold(*gc_thresholds)
+        install_gc_manager()
         run_command()
 
     # make sure that we run the reactor with the sentinel log context,
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index dd76e073..efedcc88 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -131,9 +131,18 @@ class SynapseHomeServer(HomeServer):
         resources.update(self._module_web_resources)
         self._module_web_resources_consumed = True
 
-        # try to find something useful to redirect '/' to
-        if WEB_CLIENT_PREFIX in resources:
-            root_resource: Resource = RootOptionsRedirectResource(WEB_CLIENT_PREFIX)
+        # Try to find something useful to serve at '/':
+        #
+        # 1. Redirect to the web client if it is an HTTP(S) URL.
+        # 2. Redirect to the web client served via Synapse.
+        # 3. Redirect to the static "Synapse is running" page.
+        # 4. Do not redirect and use a blank resource.
+        if self.config.server.web_client_location_is_redirect:
+            root_resource: Resource = RootOptionsRedirectResource(
+                self.config.server.web_client_location
+            )
+        elif WEB_CLIENT_PREFIX in resources:
+            root_resource = RootOptionsRedirectResource(WEB_CLIENT_PREFIX)
         elif STATIC_PREFIX in resources:
             root_resource = RootOptionsRedirectResource(STATIC_PREFIX)
         else:
@@ -262,15 +271,15 @@ class SynapseHomeServer(HomeServer):
             resources[SERVER_KEY_V2_PREFIX] = KeyApiV2Resource(self)
 
         if name == "webclient":
+            # webclient listeners are deprecated as of Synapse v1.51.0, remove it
+            # in > v1.53.0.
             webclient_loc = self.config.server.web_client_location
 
             if webclient_loc is None:
                 logger.warning(
                     "Not enabling webclient resource, as web_client_location is unset."
                 )
-            elif webclient_loc.startswith("http://") or webclient_loc.startswith(
-                "https://"
-            ):
+            elif self.config.server.web_client_location_is_redirect:
                 resources[WEB_CLIENT_PREFIX] = RootRedirect(webclient_loc)
             else:
                 logger.warning(
diff --git a/synapse/config/api.py b/synapse/config/api.py
index 25538b82..8133b6b6 100644
--- a/synapse/config/api.py
+++ b/synapse/config/api.py
@@ -29,6 +29,7 @@ class ApiConfig(Config):
     def read_config(self, config: JsonDict, **kwargs):
         validate_config(_MAIN_SCHEMA, config, ())
         self.room_prejoin_state = list(self._get_prejoin_state_types(config))
+        self.track_puppeted_user_ips = config.get("track_puppeted_user_ips", False)
 
     def generate_config_section(cls, **kwargs) -> str:
         formatted_default_state_types = "\n".join(
@@ -59,6 +60,21 @@ class ApiConfig(Config):
            #
            #additional_event_types:
            #  - org.example.custom.event.type
+
+        # We record the IP address of clients used to access the API for various
+        # reasons, including displaying it to the user in the "Where you're signed in"
+        # dialog.
+        #
+        # By default, when puppeting another user via the admin API, the client IP
+        # address is recorded against the user who created the access token (ie, the
+        # admin user), and *not* the puppeted user.
+        #
+        # Uncomment the following to also record the IP address against the puppeted
+        # user. (This also means that the puppeted user will count as an "active" user
+        # for the purpose of monthly active user tracking - see 'limit_usage_by_mau' etc
+        # above.)
+        #
+        #track_puppeted_user_ips: true
         """ % {
             "formatted_default_state_types": formatted_default_state_types
         }
@@ -138,5 +154,8 @@ _MAIN_SCHEMA = {
     "properties": {
         "room_prejoin_state": _ROOM_PREJOIN_STATE_CONFIG_SCHEMA,
         "room_invite_state_types": _ROOM_INVITE_STATE_TYPES_SCHEMA,
+        "track_puppeted_user_ips": {
+            "type": "boolean",
+        },
     },
 }
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index 510b647c..949d7dd5 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -55,19 +55,19 @@ https://matrix-org.github.io/synapse/latest/templates.html
 ---------------------------------------------------------------------------------------"""
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class EmailSubjectConfig:
-    message_from_person_in_room = attr.ib(type=str)
-    message_from_person = attr.ib(type=str)
-    messages_from_person = attr.ib(type=str)
-    messages_in_room = attr.ib(type=str)
-    messages_in_room_and_others = attr.ib(type=str)
-    messages_from_person_and_others = attr.ib(type=str)
-    invite_from_person = attr.ib(type=str)
-    invite_from_person_to_room = attr.ib(type=str)
-    invite_from_person_to_space = attr.ib(type=str)
-    password_reset = attr.ib(type=str)
-    email_validation = attr.ib(type=str)
+    message_from_person_in_room: str
+    message_from_person: str
+    messages_from_person: str
+    messages_in_room: str
+    messages_in_room_and_others: str
+    messages_from_person_and_others: str
+    invite_from_person: str
+    invite_from_person_to_room: str
+    invite_from_person_to_space: str
+    password_reset: str
+    email_validation: str
 
 
 class EmailConfig(Config):
diff --git a/synapse/config/oidc.py b/synapse/config/oidc.py
index 79c400fe..e783b113 100644
--- a/synapse/config/oidc.py
+++ b/synapse/config/oidc.py
@@ -148,10 +148,13 @@ class OIDCConfig(Config):
         #       Defaults to false. Avoid this in production.
         #
         #   user_profile_method: Whether to fetch the user profile from the userinfo
-        #       endpoint. Valid values are: 'auto' or 'userinfo_endpoint'.
+        #       endpoint, or to rely on the data returned in the id_token from the
+        #       token_endpoint.
         #
-        #       Defaults to 'auto', which fetches the userinfo endpoint if 'openid' is
-        #       included in 'scopes'. Set to 'userinfo_endpoint' to always fetch the
+        #       Valid values are: 'auto' or 'userinfo_endpoint'.
+        #
+        #       Defaults to 'auto', which uses the userinfo endpoint if 'openid' is
+        #       not included in 'scopes'. Set to 'userinfo_endpoint' to always use the
         #       userinfo endpoint.
         #
         #   allow_existing_users: set to 'true' to allow a user logging in via OIDC to
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 1de2dea9..f200d0c1 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -200,8 +200,8 @@ class HttpListenerConfig:
     """Object describing the http-specific parts of the config of a listener"""
 
     x_forwarded: bool = False
-    resources: List[HttpResourceConfig] = attr.ib(factory=list)
-    additional_resources: Dict[str, dict] = attr.ib(factory=dict)
+    resources: List[HttpResourceConfig] = attr.Factory(list)
+    additional_resources: Dict[str, dict] = attr.Factory(dict)
     tag: Optional[str] = None
 
 
@@ -259,7 +259,6 @@ class ServerConfig(Config):
             raise ConfigError(str(e))
 
         self.pid_file = self.abspath(config.get("pid_file"))
-        self.web_client_location = config.get("web_client_location", None)
         self.soft_file_limit = config.get("soft_file_limit", 0)
         self.daemonize = config.get("daemonize")
         self.print_pidfile = config.get("print_pidfile")
@@ -506,8 +505,17 @@ class ServerConfig(Config):
                     l2.append(listener)
             self.listeners = l2
 
-        if not self.web_client_location:
-            _warn_if_webclient_configured(self.listeners)
+        self.web_client_location = config.get("web_client_location", None)
+        self.web_client_location_is_redirect = self.web_client_location and (
+            self.web_client_location.startswith("http://")
+            or self.web_client_location.startswith("https://")
+        )
+        # A non-HTTP(S) web client location is deprecated.
+        if self.web_client_location and not self.web_client_location_is_redirect:
+            logger.warning(NO_MORE_NONE_HTTP_WEB_CLIENT_LOCATION_WARNING)
+
+        # Warn if webclient is configured for a worker.
+        _warn_if_webclient_configured(self.listeners)
 
         self.gc_thresholds = read_gc_thresholds(config.get("gc_thresholds", None))
         self.gc_seconds = self.read_gc_intervals(config.get("gc_min_interval", None))
@@ -793,13 +801,7 @@ class ServerConfig(Config):
         #
         pid_file: %(pid_file)s
 
-        # The absolute URL to the web client which /_matrix/client will redirect
-        # to if 'webclient' is configured under the 'listeners' configuration.
-        #
-        # This option can be also set to the filesystem path to the web client
-        # which will be served at /_matrix/client/ if 'webclient' is configured
-        # under the 'listeners' configuration, however this is a security risk:
-        # https://github.com/matrix-org/synapse#security-note
+        # The absolute URL to the web client which / will redirect to.
         #
         #web_client_location: https://riot.example.com/
 
@@ -883,7 +885,7 @@ class ServerConfig(Config):
         # The default room version for newly created rooms.
         #
         # Known room versions are listed here:
-        # https://matrix.org/docs/spec/#complete-list-of-room-versions
+        # https://spec.matrix.org/latest/rooms/#complete-list-of-room-versions
         #
         # For example, for room version 1, default_room_version should be set
         # to "1".
@@ -1011,8 +1013,6 @@ class ServerConfig(Config):
         #   static: static resources under synapse/static (/_matrix/static). (Mostly
         #       useful for 'fallback authentication'.)
         #
-        #   webclient: A web client. Requires web_client_location to be set.
-        #
         listeners:
           # TLS-enabled listener: for when matrix traffic is sent directly to synapse.
           #
@@ -1349,9 +1349,15 @@ def parse_listener_def(listener: Any) -> ListenerConfig:
     return ListenerConfig(port, bind_addresses, listener_type, tls, http_config)
 
 
+NO_MORE_NONE_HTTP_WEB_CLIENT_LOCATION_WARNING = """
+Synapse no longer supports serving a web client. To remove this warning,
+configure 'web_client_location' with an HTTP(S) URL.
+"""
+
+
 NO_MORE_WEB_CLIENT_WARNING = """
-Synapse no longer includes a web client. To enable a web client, configure
-web_client_location. To remove this warning, remove 'webclient' from the 'listeners'
+Synapse no longer includes a web client. To redirect the root resource to a web client, configure
+'web_client_location'. To remove this warning, remove 'webclient' from the 'listeners'
 configuration.
 """
 
diff --git a/synapse/config/workers.py b/synapse/config/workers.py
index 576f5191..bdaba6db 100644
--- a/synapse/config/workers.py
+++ b/synapse/config/workers.py
@@ -51,12 +51,12 @@ def _instance_to_list_converter(obj: Union[str, List[str]]) -> List[str]:
     return obj
 
 
-@attr.s
+@attr.s(auto_attribs=True)
 class InstanceLocationConfig:
     """The host and port to talk to an instance via HTTP replication."""
 
-    host = attr.ib(type=str)
-    port = attr.ib(type=int)
+    host: str
+    port: int
 
 
 @attr.s
@@ -77,34 +77,28 @@ class WriterLocations:
             can only be a single instance.
     """
 
-    events = attr.ib(
+    events: List[str] = attr.ib(
         default=["master"],
-        type=List[str],
         converter=_instance_to_list_converter,
     )
-    typing = attr.ib(
+    typing: List[str] = attr.ib(
         default=["master"],
-        type=List[str],
         converter=_instance_to_list_converter,
     )
-    to_device = attr.ib(
+    to_device: List[str] = attr.ib(
         default=["master"],
-        type=List[str],
         converter=_instance_to_list_converter,
     )
-    account_data = attr.ib(
+    account_data: List[str] = attr.ib(
         default=["master"],
-        type=List[str],
         converter=_instance_to_list_converter,
     )
-    receipts = attr.ib(
+    receipts: List[str] = attr.ib(
         default=["master"],
-        type=List[str],
         converter=_instance_to_list_converter,
     )
-    presence = attr.ib(
+    presence: List[str] = attr.ib(
         default=["master"],
-        type=List[str],
         converter=_instance_to_list_converter,
     )
 
diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index 993b0409..72d4a69a 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -58,7 +58,7 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-@attr.s(slots=True, cmp=False)
+@attr.s(slots=True, frozen=True, cmp=False, auto_attribs=True)
 class VerifyJsonRequest:
     """
     A request to verify a JSON object.
@@ -78,10 +78,10 @@ class VerifyJsonRequest:
         key_ids: The set of key_ids to that could be used to verify the JSON object
     """
 
-    server_name = attr.ib(type=str)
-    get_json_object = attr.ib(type=Callable[[], JsonDict])
-    minimum_valid_until_ts = attr.ib(type=int)
-    key_ids = attr.ib(type=List[str])
+    server_name: str
+    get_json_object: Callable[[], JsonDict]
+    minimum_valid_until_ts: int
+    key_ids: List[str]
 
     @staticmethod
     def from_json_object(
@@ -124,7 +124,7 @@ class KeyLookupError(ValueError):
     pass
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class _FetchKeyRequest:
     """A request for keys for a given server.
 
@@ -138,9 +138,9 @@ class _FetchKeyRequest:
         key_ids: The IDs of the keys to attempt to fetch
     """
 
-    server_name = attr.ib(type=str)
-    minimum_valid_until_ts = attr.ib(type=int)
-    key_ids = attr.ib(type=List[str])
+    server_name: str
+    minimum_valid_until_ts: int
+    key_ids: List[str]
 
 
 class Keyring:
diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index f251402e..0eab1aef 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -28,7 +28,7 @@ if TYPE_CHECKING:
     from synapse.storage.databases.main import DataStore
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class EventContext:
     """
     Holds information relevant to persisting an event
@@ -103,15 +103,15 @@ class EventContext:
             accessed via get_prev_state_ids.
     """
 
-    rejected = attr.ib(default=False, type=Union[bool, str])
-    _state_group = attr.ib(default=None, type=Optional[int])
-    state_group_before_event = attr.ib(default=None, type=Optional[int])
-    prev_group = attr.ib(default=None, type=Optional[int])
-    delta_ids = attr.ib(default=None, type=Optional[StateMap[str]])
-    app_service = attr.ib(default=None, type=Optional[ApplicationService])
+    rejected: Union[bool, str] = False
+    _state_group: Optional[int] = None
+    state_group_before_event: Optional[int] = None
+    prev_group: Optional[int] = None
+    delta_ids: Optional[StateMap[str]] = None
+    app_service: Optional[ApplicationService] = None
 
-    _current_state_ids = attr.ib(default=None, type=Optional[StateMap[str]])
-    _prev_state_ids = attr.ib(default=None, type=Optional[StateMap[str]])
+    _current_state_ids: Optional[StateMap[str]] = None
+    _prev_state_ids: Optional[StateMap[str]] = None
 
     @staticmethod
     def with_state(
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 2038e729..918adeec 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -14,17 +14,7 @@
 # limitations under the License.
 import collections.abc
 import re
-from typing import (
-    TYPE_CHECKING,
-    Any,
-    Callable,
-    Dict,
-    Iterable,
-    List,
-    Mapping,
-    Optional,
-    Union,
-)
+from typing import Any, Callable, Dict, Iterable, List, Mapping, Optional, Union
 
 from frozendict import frozendict
 
@@ -32,14 +22,10 @@ from synapse.api.constants import EventContentFields, EventTypes, RelationTypes
 from synapse.api.errors import Codes, SynapseError
 from synapse.api.room_versions import RoomVersion
 from synapse.types import JsonDict
-from synapse.util.async_helpers import yieldable_gather_results
 from synapse.util.frozenutils import unfreeze
 
 from . import EventBase
 
-if TYPE_CHECKING:
-    from synapse.server import HomeServer
-
 # Split strings on "." but not "\." This uses a negative lookbehind assertion for '\'
 # (?<!stuff) matches if the current position in the string is not preceded
 # by a match for 'stuff'.
@@ -385,17 +371,12 @@ class EventClientSerializer:
     clients.
     """
 
-    def __init__(self, hs: "HomeServer"):
-        self.store = hs.get_datastore()
-        self._msc1849_enabled = hs.config.experimental.msc1849_enabled
-        self._msc3440_enabled = hs.config.experimental.msc3440_enabled
-
-    async def serialize_event(
+    def serialize_event(
         self,
         event: Union[JsonDict, EventBase],
         time_now: int,
         *,
-        bundle_aggregations: bool = False,
+        bundle_aggregations: Optional[Dict[str, JsonDict]] = None,
         **kwargs: Any,
     ) -> JsonDict:
         """Serializes a single event.
@@ -418,66 +399,41 @@ class EventClientSerializer:
         serialized_event = serialize_event(event, time_now, **kwargs)
 
         # Check if there are any bundled aggregations to include with the event.
-        #
-        # Do not bundle aggregations if any of the following at true:
-        #
-        # * Support is disabled via the configuration or the caller.
-        # * The event is a state event.
-        # * The event has been redacted.
-        if (
-            self._msc1849_enabled
-            and bundle_aggregations
-            and not event.is_state()
-            and not event.internal_metadata.is_redacted()
-        ):
-            await self._injected_bundled_aggregations(event, time_now, serialized_event)
+        if bundle_aggregations:
+            event_aggregations = bundle_aggregations.get(event.event_id)
+            if event_aggregations:
+                self._inject_bundled_aggregations(
+                    event,
+                    time_now,
+                    bundle_aggregations[event.event_id],
+                    serialized_event,
+                )
 
         return serialized_event
 
-    async def _injected_bundled_aggregations(
-        self, event: EventBase, time_now: int, serialized_event: JsonDict
+    def _inject_bundled_aggregations(
+        self,
+        event: EventBase,
+        time_now: int,
+        aggregations: JsonDict,
+        serialized_event: JsonDict,
     ) -> None:
         """Potentially injects bundled aggregations into the unsigned portion of the serialized event.
 
         Args:
             event: The event being serialized.
             time_now: The current time in milliseconds
+            aggregations: The bundled aggregation to serialize.
             serialized_event: The serialized event which may be modified.
 
         """
-        # Do not bundle aggregations for an event which represents an edit or an
-        # annotation. It does not make sense for them to have related events.
-        relates_to = event.content.get("m.relates_to")
-        if isinstance(relates_to, (dict, frozendict)):
-            relation_type = relates_to.get("rel_type")
-            if relation_type in (RelationTypes.ANNOTATION, RelationTypes.REPLACE):
-                return
-
-        event_id = event.event_id
-        room_id = event.room_id
-
-        # The bundled aggregations to include.
-        aggregations = {}
-
-        annotations = await self.store.get_aggregation_groups_for_event(
-            event_id, room_id
-        )
-        if annotations.chunk:
-            aggregations[RelationTypes.ANNOTATION] = annotations.to_dict()
+        # Make a copy in-case the object is cached.
+        aggregations = aggregations.copy()
 
-        references = await self.store.get_relations_for_event(
-            event_id, room_id, RelationTypes.REFERENCE, direction="f"
-        )
-        if references.chunk:
-            aggregations[RelationTypes.REFERENCE] = references.to_dict()
-
-        edit = None
-        if event.type == EventTypes.Message:
-            edit = await self.store.get_applicable_edit(event_id, room_id)
-
-        if edit:
+        if RelationTypes.REPLACE in aggregations:
             # If there is an edit replace the content, preserving existing
             # relations.
+            edit = aggregations[RelationTypes.REPLACE]
 
             # Ensure we take copies of the edit content, otherwise we risk modifying
             # the original event.
@@ -502,27 +458,19 @@ class EventClientSerializer:
             }
 
         # If this event is the start of a thread, include a summary of the replies.
-        if self._msc3440_enabled:
-            (
-                thread_count,
-                latest_thread_event,
-            ) = await self.store.get_thread_summary(event_id, room_id)
-            if latest_thread_event:
-                aggregations[RelationTypes.THREAD] = {
-                    # Don't bundle aggregations as this could recurse forever.
-                    "latest_event": await self.serialize_event(
-                        latest_thread_event, time_now, bundle_aggregations=False
-                    ),
-                    "count": thread_count,
-                }
-
-        # If any bundled aggregations were found, include them.
-        if aggregations:
-            serialized_event["unsigned"].setdefault("m.relations", {}).update(
-                aggregations
+        if RelationTypes.THREAD in aggregations:
+            # Serialize the latest thread event.
+            latest_thread_event = aggregations[RelationTypes.THREAD]["latest_event"]
+
+            # Don't bundle aggregations as this could recurse forever.
+            aggregations[RelationTypes.THREAD]["latest_event"] = self.serialize_event(
+                latest_thread_event, time_now, bundle_aggregations=None
             )
 
-    async def serialize_events(
+        # Include the bundled aggregations in the event.
+        serialized_event["unsigned"].setdefault("m.relations", {}).update(aggregations)
+
+    def serialize_events(
         self, events: Iterable[Union[JsonDict, EventBase]], time_now: int, **kwargs: Any
     ) -> List[JsonDict]:
         """Serializes multiple events.
@@ -535,9 +483,9 @@ class EventClientSerializer:
         Returns:
             The list of serialized events
         """
-        return await yieldable_gather_results(
-            self.serialize_event, events, time_now=time_now, **kwargs
-        )
+        return [
+            self.serialize_event(event, time_now=time_now, **kwargs) for event in events
+        ]
 
 
 def copy_power_levels_contents(
diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index addc0bf0..896168c0 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -230,6 +230,10 @@ def event_from_pdu_json(pdu_json: JsonDict, room_version: RoomVersion) -> EventB
     # origin, etc etc)
     assert_params_in_dict(pdu_json, ("type", "depth"))
 
+    # Strip any unauthorized values from "unsigned" if they exist
+    if "unsigned" in pdu_json:
+        _strip_unsigned_values(pdu_json)
+
     depth = pdu_json["depth"]
     if not isinstance(depth, int):
         raise SynapseError(400, "Depth %r not an intger" % (depth,), Codes.BAD_JSON)
@@ -245,3 +249,24 @@ def event_from_pdu_json(pdu_json: JsonDict, room_version: RoomVersion) -> EventB
 
     event = make_event_from_dict(pdu_json, room_version)
     return event
+
+
+def _strip_unsigned_values(pdu_dict: JsonDict) -> None:
+    """
+    Strip any unsigned values unless specifically allowed, as defined by the whitelist.
+
+    pdu: the json dict to strip values from. Note that the dict is mutated by this
+    function
+    """
+    unsigned = pdu_dict["unsigned"]
+
+    if not isinstance(unsigned, dict):
+        pdu_dict["unsigned"] = {}
+
+    if pdu_dict["type"] == "m.room.member":
+        whitelist = ["knock_room_state", "invite_room_state", "age"]
+    else:
+        whitelist = ["age"]
+
+    filtered_unsigned = {k: v for k, v in unsigned.items() if k in whitelist}
+    pdu_dict["unsigned"] = filtered_unsigned
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 6ea4edfc..74f17aa4 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -56,7 +56,6 @@ from synapse.api.room_versions import (
 from synapse.events import EventBase, builder
 from synapse.federation.federation_base import FederationBase, event_from_pdu_json
 from synapse.federation.transport.client import SendJoinResponse
-from synapse.logging.utils import log_function
 from synapse.types import JsonDict, get_domain_from_id
 from synapse.util.async_helpers import concurrently_execute
 from synapse.util.caches.expiringcache import ExpiringCache
@@ -119,7 +118,8 @@ class FederationClient(FederationBase):
         # It is a map of (room ID, suggested-only) -> the response of
         # get_room_hierarchy.
         self._get_room_hierarchy_cache: ExpiringCache[
-            Tuple[str, bool], Tuple[JsonDict, Sequence[JsonDict], Sequence[str]]
+            Tuple[str, bool],
+            Tuple[JsonDict, Sequence[JsonDict], Sequence[JsonDict], Sequence[str]],
         ] = ExpiringCache(
             cache_name="get_room_hierarchy_cache",
             clock=self._clock,
@@ -144,7 +144,6 @@ class FederationClient(FederationBase):
             if destination_dict:
                 self.pdu_destination_tried[event_id] = destination_dict
 
-    @log_function
     async def make_query(
         self,
         destination: str,
@@ -178,7 +177,6 @@ class FederationClient(FederationBase):
             ignore_backoff=ignore_backoff,
         )
 
-    @log_function
     async def query_client_keys(
         self, destination: str, content: JsonDict, timeout: int
     ) -> JsonDict:
@@ -196,7 +194,6 @@ class FederationClient(FederationBase):
             destination, content, timeout
         )
 
-    @log_function
     async def query_user_devices(
         self, destination: str, user_id: str, timeout: int = 30000
     ) -> JsonDict:
@@ -208,7 +205,6 @@ class FederationClient(FederationBase):
             destination, user_id, timeout
         )
 
-    @log_function
     async def claim_client_keys(
         self, destination: str, content: JsonDict, timeout: int
     ) -> JsonDict:
@@ -1338,7 +1334,7 @@ class FederationClient(FederationBase):
         destinations: Iterable[str],
         room_id: str,
         suggested_only: bool,
-    ) -> Tuple[JsonDict, Sequence[JsonDict], Sequence[str]]:
+    ) -> Tuple[JsonDict, Sequence[JsonDict], Sequence[JsonDict], Sequence[str]]:
         """
         Call other servers to get a hierarchy of the given room.
 
@@ -1353,7 +1349,8 @@ class FederationClient(FederationBase):
 
         Returns:
             A tuple of:
-                The room as a JSON dictionary.
+                The room as a JSON dictionary, without a "children_state" key.
+                A list of `m.space.child` state events.
                 A list of children rooms, as JSON dictionaries.
                 A list of inaccessible children room IDs.
 
@@ -1368,7 +1365,7 @@ class FederationClient(FederationBase):
 
         async def send_request(
             destination: str,
-        ) -> Tuple[JsonDict, Sequence[JsonDict], Sequence[str]]:
+        ) -> Tuple[JsonDict, Sequence[JsonDict], Sequence[JsonDict], Sequence[str]]:
             try:
                 res = await self.transport_layer.get_room_hierarchy(
                     destination=destination,
@@ -1397,7 +1394,7 @@ class FederationClient(FederationBase):
                 raise InvalidResponseError("'room' must be a dict")
 
             # Validate children_state of the room.
-            children_state = room.get("children_state", [])
+            children_state = room.pop("children_state", [])
             if not isinstance(children_state, Sequence):
                 raise InvalidResponseError("'room.children_state' must be a list")
             if any(not isinstance(e, dict) for e in children_state):
@@ -1426,7 +1423,7 @@ class FederationClient(FederationBase):
                     "Invalid room ID in 'inaccessible_children' list"
                 )
 
-            return room, children, inaccessible_children
+            return room, children_state, children, inaccessible_children
 
         try:
             result = await self._try_destination_list(
@@ -1474,8 +1471,6 @@ class FederationClient(FederationBase):
                 if event.room_id == room_id:
                     children_events.append(event.data)
                     children_room_ids.add(event.state_key)
-            # And add them under the requested room.
-            requested_room["children_state"] = children_events
 
             # Find the children rooms.
             children = []
@@ -1485,7 +1480,7 @@ class FederationClient(FederationBase):
 
             # It isn't clear from the response whether some of the rooms are
             # not accessible.
-            result = (requested_room, children, ())
+            result = (requested_room, children_events, children, ())
 
         # Cache the result to avoid fetching data over federation every time.
         self._get_room_hierarchy_cache[(room_id, suggested_only)] = result
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index ee71f289..af9cb98f 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -58,7 +58,6 @@ from synapse.logging.context import (
     run_in_background,
 )
 from synapse.logging.opentracing import log_kv, start_active_span_from_edu, trace
-from synapse.logging.utils import log_function
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.replication.http.federation import (
     ReplicationFederationSendEduRestServlet,
@@ -859,7 +858,6 @@ class FederationServer(FederationBase):
             res = {"auth_chain": [a.get_pdu_json(time_now) for a in auth_pdus]}
         return 200, res
 
-    @log_function
     async def on_query_client_keys(
         self, origin: str, content: Dict[str, str]
     ) -> Tuple[int, Dict[str, Any]]:
@@ -940,7 +938,6 @@ class FederationServer(FederationBase):
 
         return {"events": [ev.get_pdu_json(time_now) for ev in missing_events]}
 
-    @log_function
     async def on_openid_userinfo(self, token: str) -> Optional[str]:
         ts_now_ms = self._clock.time_msec()
         return await self.store.get_user_id_for_open_id_token(token, ts_now_ms)
diff --git a/synapse/federation/persistence.py b/synapse/federation/persistence.py
index 523ab1c5..60e2e6cf 100644
--- a/synapse/federation/persistence.py
+++ b/synapse/federation/persistence.py
@@ -23,7 +23,6 @@ import logging
 from typing import Optional, Tuple
 
 from synapse.federation.units import Transaction
-from synapse.logging.utils import log_function
 from synapse.storage.databases.main import DataStore
 from synapse.types import JsonDict
 
@@ -36,7 +35,6 @@ class TransactionActions:
     def __init__(self, datastore: DataStore):
         self.store = datastore
 
-    @log_function
     async def have_responded(
         self, origin: str, transaction: Transaction
     ) -> Optional[Tuple[int, JsonDict]]:
@@ -53,7 +51,6 @@ class TransactionActions:
 
         return await self.store.get_received_txn_response(transaction_id, origin)
 
-    @log_function
     async def set_response(
         self, origin: str, transaction: Transaction, code: int, response: JsonDict
     ) -> None:
diff --git a/synapse/federation/sender/per_destination_queue.py b/synapse/federation/sender/per_destination_queue.py
index 391b30fb..8152e80b 100644
--- a/synapse/federation/sender/per_destination_queue.py
+++ b/synapse/federation/sender/per_destination_queue.py
@@ -607,18 +607,18 @@ class PerDestinationQueue:
         self._pending_pdus = []
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _TransactionQueueManager:
     """A helper async context manager for pulling stuff off the queues and
     tracking what was last successfully sent, etc.
     """
 
-    queue = attr.ib(type=PerDestinationQueue)
+    queue: PerDestinationQueue
 
-    _device_stream_id = attr.ib(type=Optional[int], default=None)
-    _device_list_id = attr.ib(type=Optional[int], default=None)
-    _last_stream_ordering = attr.ib(type=Optional[int], default=None)
-    _pdus = attr.ib(type=List[EventBase], factory=list)
+    _device_stream_id: Optional[int] = None
+    _device_list_id: Optional[int] = None
+    _last_stream_ordering: Optional[int] = None
+    _pdus: List[EventBase] = attr.Factory(list)
 
     async def __aenter__(self) -> Tuple[List[EventBase], List[Edu]]:
         # First we calculate the EDUs we want to send, if any.
diff --git a/synapse/federation/sender/transaction_manager.py b/synapse/federation/sender/transaction_manager.py
index ab935e5a..742ee572 100644
--- a/synapse/federation/sender/transaction_manager.py
+++ b/synapse/federation/sender/transaction_manager.py
@@ -35,6 +35,7 @@ if TYPE_CHECKING:
     import synapse.server
 
 logger = logging.getLogger(__name__)
+issue_8631_logger = logging.getLogger("synapse.8631_debug")
 
 last_pdu_ts_metric = Gauge(
     "synapse_federation_last_sent_pdu_time",
@@ -124,6 +125,17 @@ class TransactionManager:
                 len(pdus),
                 len(edus),
             )
+            if issue_8631_logger.isEnabledFor(logging.DEBUG):
+                DEVICE_UPDATE_EDUS = {"m.device_list_update", "m.signing_key_update"}
+                device_list_updates = [
+                    edu.content for edu in edus if edu.edu_type in DEVICE_UPDATE_EDUS
+                ]
+                if device_list_updates:
+                    issue_8631_logger.debug(
+                        "about to send txn [%s] including device list updates: %s",
+                        transaction.transaction_id,
+                        device_list_updates,
+                    )
 
             # Actually send the transaction
 
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 9fc4c31c..8782586c 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -44,7 +44,6 @@ from synapse.api.urls import (
 from synapse.events import EventBase, make_event_from_dict
 from synapse.federation.units import Transaction
 from synapse.http.matrixfederationclient import ByteParser
-from synapse.logging.utils import log_function
 from synapse.types import JsonDict
 
 logger = logging.getLogger(__name__)
@@ -62,7 +61,6 @@ class TransportLayerClient:
         self.server_name = hs.hostname
         self.client = hs.get_federation_http_client()
 
-    @log_function
     async def get_room_state_ids(
         self, destination: str, room_id: str, event_id: str
     ) -> JsonDict:
@@ -88,7 +86,6 @@ class TransportLayerClient:
             try_trailing_slash_on_400=True,
         )
 
-    @log_function
     async def get_event(
         self, destination: str, event_id: str, timeout: Optional[int] = None
     ) -> JsonDict:
@@ -111,7 +108,6 @@ class TransportLayerClient:
             destination, path=path, timeout=timeout, try_trailing_slash_on_400=True
         )
 
-    @log_function
     async def backfill(
         self, destination: str, room_id: str, event_tuples: Collection[str], limit: int
     ) -> Optional[JsonDict]:
@@ -149,7 +145,6 @@ class TransportLayerClient:
             destination, path=path, args=args, try_trailing_slash_on_400=True
         )
 
-    @log_function
     async def timestamp_to_event(
         self, destination: str, room_id: str, timestamp: int, direction: str
     ) -> Union[JsonDict, List]:
@@ -185,7 +180,6 @@ class TransportLayerClient:
 
         return remote_response
 
-    @log_function
     async def send_transaction(
         self,
         transaction: Transaction,
@@ -234,7 +228,6 @@ class TransportLayerClient:
             try_trailing_slash_on_400=True,
         )
 
-    @log_function
     async def make_query(
         self,
         destination: str,
@@ -254,7 +247,6 @@ class TransportLayerClient:
             ignore_backoff=ignore_backoff,
         )
 
-    @log_function
     async def make_membership_event(
         self,
         destination: str,
@@ -317,7 +309,6 @@ class TransportLayerClient:
             ignore_backoff=ignore_backoff,
         )
 
-    @log_function
     async def send_join_v1(
         self,
         room_version: RoomVersion,
@@ -336,7 +327,6 @@ class TransportLayerClient:
             max_response_size=MAX_RESPONSE_SIZE_SEND_JOIN,
         )
 
-    @log_function
     async def send_join_v2(
         self,
         room_version: RoomVersion,
@@ -355,7 +345,6 @@ class TransportLayerClient:
             max_response_size=MAX_RESPONSE_SIZE_SEND_JOIN,
         )
 
-    @log_function
     async def send_leave_v1(
         self, destination: str, room_id: str, event_id: str, content: JsonDict
     ) -> Tuple[int, JsonDict]:
@@ -372,7 +361,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def send_leave_v2(
         self, destination: str, room_id: str, event_id: str, content: JsonDict
     ) -> JsonDict:
@@ -389,7 +377,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def send_knock_v1(
         self,
         destination: str,
@@ -423,7 +410,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content
         )
 
-    @log_function
     async def send_invite_v1(
         self, destination: str, room_id: str, event_id: str, content: JsonDict
     ) -> Tuple[int, JsonDict]:
@@ -433,7 +419,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     async def send_invite_v2(
         self, destination: str, room_id: str, event_id: str, content: JsonDict
     ) -> JsonDict:
@@ -443,7 +428,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     async def get_public_rooms(
         self,
         remote_server: str,
@@ -516,7 +500,6 @@ class TransportLayerClient:
 
         return response
 
-    @log_function
     async def exchange_third_party_invite(
         self, destination: str, room_id: str, event_dict: JsonDict
     ) -> JsonDict:
@@ -526,7 +509,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=event_dict
         )
 
-    @log_function
     async def get_event_auth(
         self, destination: str, room_id: str, event_id: str
     ) -> JsonDict:
@@ -534,7 +516,6 @@ class TransportLayerClient:
 
         return await self.client.get_json(destination=destination, path=path)
 
-    @log_function
     async def query_client_keys(
         self, destination: str, query_content: JsonDict, timeout: int
     ) -> JsonDict:
@@ -576,7 +557,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=query_content, timeout=timeout
         )
 
-    @log_function
     async def query_user_devices(
         self, destination: str, user_id: str, timeout: int
     ) -> JsonDict:
@@ -616,7 +596,6 @@ class TransportLayerClient:
             destination=destination, path=path, timeout=timeout
         )
 
-    @log_function
     async def claim_client_keys(
         self, destination: str, query_content: JsonDict, timeout: int
     ) -> JsonDict:
@@ -655,7 +634,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=query_content, timeout=timeout
         )
 
-    @log_function
     async def get_missing_events(
         self,
         destination: str,
@@ -680,7 +658,6 @@ class TransportLayerClient:
             timeout=timeout,
         )
 
-    @log_function
     async def get_group_profile(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -694,7 +671,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def update_group_profile(
         self, destination: str, group_id: str, requester_user_id: str, content: JsonDict
     ) -> JsonDict:
@@ -716,7 +692,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_group_summary(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -730,7 +705,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_rooms_in_group(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -798,7 +772,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_users_in_group(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -812,7 +785,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_invited_users_in_group(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -826,7 +798,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def accept_group_invite(
         self, destination: str, group_id: str, user_id: str, content: JsonDict
     ) -> JsonDict:
@@ -837,7 +808,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     def join_group(
         self, destination: str, group_id: str, user_id: str, content: JsonDict
     ) -> Awaitable[JsonDict]:
@@ -848,7 +818,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     async def invite_to_group(
         self,
         destination: str,
@@ -868,7 +837,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def invite_to_group_notification(
         self, destination: str, group_id: str, user_id: str, content: JsonDict
     ) -> JsonDict:
@@ -882,7 +850,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     async def remove_user_from_group(
         self,
         destination: str,
@@ -902,7 +869,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def remove_user_from_group_notification(
         self, destination: str, group_id: str, user_id: str, content: JsonDict
     ) -> JsonDict:
@@ -916,7 +882,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     async def renew_group_attestation(
         self, destination: str, group_id: str, user_id: str, content: JsonDict
     ) -> JsonDict:
@@ -930,7 +895,6 @@ class TransportLayerClient:
             destination=destination, path=path, data=content, ignore_backoff=True
         )
 
-    @log_function
     async def update_group_summary_room(
         self,
         destination: str,
@@ -959,7 +923,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def delete_group_summary_room(
         self,
         destination: str,
@@ -986,7 +949,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_group_categories(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -1000,7 +962,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_group_category(
         self, destination: str, group_id: str, requester_user_id: str, category_id: str
     ) -> JsonDict:
@@ -1014,7 +975,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def update_group_category(
         self,
         destination: str,
@@ -1034,7 +994,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def delete_group_category(
         self, destination: str, group_id: str, requester_user_id: str, category_id: str
     ) -> JsonDict:
@@ -1048,7 +1007,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_group_roles(
         self, destination: str, group_id: str, requester_user_id: str
     ) -> JsonDict:
@@ -1062,7 +1020,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def get_group_role(
         self, destination: str, group_id: str, requester_user_id: str, role_id: str
     ) -> JsonDict:
@@ -1076,7 +1033,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def update_group_role(
         self,
         destination: str,
@@ -1096,7 +1052,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def delete_group_role(
         self, destination: str, group_id: str, requester_user_id: str, role_id: str
     ) -> JsonDict:
@@ -1110,7 +1065,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def update_group_summary_user(
         self,
         destination: str,
@@ -1136,7 +1090,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def set_group_join_policy(
         self, destination: str, group_id: str, requester_user_id: str, content: JsonDict
     ) -> JsonDict:
@@ -1151,7 +1104,6 @@ class TransportLayerClient:
             ignore_backoff=True,
         )
 
-    @log_function
     async def delete_group_summary_user(
         self,
         destination: str,
diff --git a/synapse/federation/transport/server/federation.py b/synapse/federation/transport/server/federation.py
index 77bfd88a..beadfa42 100644
--- a/synapse/federation/transport/server/federation.py
+++ b/synapse/federation/transport/server/federation.py
@@ -36,6 +36,7 @@ from synapse.util.ratelimitutils import FederationRateLimiter
 from synapse.util.versionstring import get_version_string
 
 logger = logging.getLogger(__name__)
+issue_8631_logger = logging.getLogger("synapse.8631_debug")
 
 
 class BaseFederationServerServlet(BaseFederationServlet):
@@ -95,6 +96,20 @@ class FederationSendServlet(BaseFederationServerServlet):
                 len(transaction_data.get("edus", [])),
             )
 
+            if issue_8631_logger.isEnabledFor(logging.DEBUG):
+                DEVICE_UPDATE_EDUS = {"m.device_list_update", "m.signing_key_update"}
+                device_list_updates = [
+                    edu.content
+                    for edu in transaction_data.get("edus", [])
+                    if edu.edu_type in DEVICE_UPDATE_EDUS
+                ]
+                if device_list_updates:
+                    issue_8631_logger.debug(
+                        "received transaction [%s] including device list updates: %s",
+                        transaction_id,
+                        device_list_updates,
+                    )
+
         except Exception as e:
             logger.exception(e)
             return 400, {"error": "Invalid transaction"}
diff --git a/synapse/handlers/account_data.py b/synapse/handlers/account_data.py
index 96273e2f..bad48713 100644
--- a/synapse/handlers/account_data.py
+++ b/synapse/handlers/account_data.py
@@ -77,7 +77,7 @@ class AccountDataHandler:
     async def add_account_data_for_user(
         self, user_id: str, account_data_type: str, content: JsonDict
     ) -> int:
-        """Add some account_data to a room for a user.
+        """Add some global account_data for a user.
 
         Args:
             user_id: The user to add a tag for.
diff --git a/synapse/handlers/admin.py b/synapse/handlers/admin.py
index 85157a13..00ab5e79 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -55,21 +55,47 @@ class AdminHandler:
 
     async def get_user(self, user: UserID) -> Optional[JsonDict]:
         """Function to get user details"""
-        ret = await self.store.get_user_by_id(user.to_string())
-        if ret:
-            profile = await self.store.get_profileinfo(user.localpart)
-            threepids = await self.store.user_get_threepids(user.to_string())
-            external_ids = [
-                ({"auth_provider": auth_provider, "external_id": external_id})
-                for auth_provider, external_id in await self.store.get_external_ids_by_user(
-                    user.to_string()
-                )
-            ]
-            ret["displayname"] = profile.display_name
-            ret["avatar_url"] = profile.avatar_url
-            ret["threepids"] = threepids
-            ret["external_ids"] = external_ids
-        return ret
+        user_info_dict = await self.store.get_user_by_id(user.to_string())
+        if user_info_dict is None:
+            return None
+
+        # Restrict returned information to a known set of fields. This prevents additional
+        # fields added to get_user_by_id from modifying Synapse's external API surface.
+        user_info_to_return = {
+            "name",
+            "admin",
+            "deactivated",
+            "shadow_banned",
+            "creation_ts",
+            "appservice_id",
+            "consent_server_notice_sent",
+            "consent_version",
+            "user_type",
+            "is_guest",
+        }
+
+        # Restrict returned keys to a known set.
+        user_info_dict = {
+            key: value
+            for key, value in user_info_dict.items()
+            if key in user_info_to_return
+        }
+
+        # Add additional user metadata
+        profile = await self.store.get_profileinfo(user.localpart)
+        threepids = await self.store.user_get_threepids(user.to_string())
+        external_ids = [
+            ({"auth_provider": auth_provider, "external_id": external_id})
+            for auth_provider, external_id in await self.store.get_external_ids_by_user(
+                user.to_string()
+            )
+        ]
+        user_info_dict["displayname"] = profile.display_name
+        user_info_dict["avatar_url"] = profile.avatar_url
+        user_info_dict["threepids"] = threepids
+        user_info_dict["external_ids"] = external_ids
+
+        return user_info_dict
 
     async def export_user_data(self, user_id: str, writer: "ExfiltrationWriter") -> Any:
         """Write all data we have on the user to the given writer.
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 84724b20..bd1a3225 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -168,25 +168,25 @@ def login_id_phone_to_thirdparty(identifier: JsonDict) -> Dict[str, str]:
     }
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class SsoLoginExtraAttributes:
     """Data we track about SAML2 sessions"""
 
     # time the session was created, in milliseconds
-    creation_time = attr.ib(type=int)
-    extra_attributes = attr.ib(type=JsonDict)
+    creation_time: int
+    extra_attributes: JsonDict
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class LoginTokenAttributes:
     """Data we store in a short-term login token"""
 
-    user_id = attr.ib(type=str)
+    user_id: str
 
-    auth_provider_id = attr.ib(type=str)
+    auth_provider_id: str
     """The SSO Identity Provider that the user authenticated with, to get this token."""
 
-    auth_provider_session_id = attr.ib(type=Optional[str])
+    auth_provider_session_id: Optional[str]
     """The session ID advertised by the SSO Identity Provider."""
 
 
@@ -2281,7 +2281,7 @@ class PasswordAuthProvider:
         # call all of the on_logged_out callbacks
         for callback in self.on_logged_out_callbacks:
             try:
-                callback(user_id, device_id, access_token)
+                await callback(user_id, device_id, access_token)
             except Exception as e:
                 logger.warning("Failed to run module API callback %s: %s", callback, e)
                 continue
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index 76654252..b184a48c 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -948,8 +948,16 @@ class DeviceListUpdater:
             devices = []
             ignore_devices = True
         else:
+            prev_stream_id = await self.store.get_device_list_last_stream_id_for_remote(
+                user_id
+            )
             cached_devices = await self.store.get_cached_devices_for_user(user_id)
-            if cached_devices == {d["device_id"]: d for d in devices}:
+
+            # To ensure that a user with no devices is cached, we skip the resync only
+            # if we have a stream_id from previously writing a cache entry.
+            if prev_stream_id is not None and cached_devices == {
+                d["device_id"]: d for d in devices
+            }:
                 logging.info(
                     "Skipping device list resync for %s, as our cache matches already",
                     user_id,
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 14360b4e..d4dfddf6 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -1321,14 +1321,14 @@ def _one_time_keys_match(old_key_json: str, new_key: JsonDict) -> bool:
     return old_key == new_key_copy
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class SignatureListItem:
     """An item in the signature list as used by upload_signatures_for_device_keys."""
 
-    signing_key_id = attr.ib(type=str)
-    target_user_id = attr.ib(type=str)
-    target_device_id = attr.ib(type=str)
-    signature = attr.ib(type=JsonDict)
+    signing_key_id: str
+    target_user_id: str
+    target_device_id: str
+    signature: JsonDict
 
 
 class SigningKeyEduUpdater:
diff --git a/synapse/handlers/events.py b/synapse/handlers/events.py
index 1b996c42..bac5de05 100644
--- a/synapse/handlers/events.py
+++ b/synapse/handlers/events.py
@@ -20,7 +20,6 @@ from synapse.api.constants import EduTypes, EventTypes, Membership
 from synapse.api.errors import AuthError, SynapseError
 from synapse.events import EventBase
 from synapse.handlers.presence import format_user_presence_state
-from synapse.logging.utils import log_function
 from synapse.streams.config import PaginationConfig
 from synapse.types import JsonDict, UserID
 from synapse.visibility import filter_events_for_client
@@ -43,7 +42,6 @@ class EventStreamHandler:
         self._server_notices_sender = hs.get_server_notices_sender()
         self._event_serializer = hs.get_event_client_serializer()
 
-    @log_function
     async def get_stream(
         self,
         auth_user_id: str,
@@ -119,7 +117,7 @@ class EventStreamHandler:
 
             events.extend(to_add)
 
-            chunks = await self._event_serializer.serialize_events(
+            chunks = self._event_serializer.serialize_events(
                 events,
                 time_now,
                 as_client_event=as_client_event,
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 26b8e3f4..a37ae0ca 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -51,7 +51,6 @@ from synapse.logging.context import (
     preserve_fn,
     run_in_background,
 )
-from synapse.logging.utils import log_function
 from synapse.replication.http.federation import (
     ReplicationCleanRoomRestServlet,
     ReplicationStoreRoomOnOutlierMembershipRestServlet,
@@ -556,7 +555,6 @@ class FederationHandler:
 
             run_in_background(self._handle_queued_pdus, room_queue)
 
-    @log_function
     async def do_knock(
         self,
         target_hosts: List[str],
@@ -928,7 +926,6 @@ class FederationHandler:
 
         return event
 
-    @log_function
     async def on_make_knock_request(
         self, origin: str, room_id: str, user_id: str
     ) -> EventBase:
@@ -1039,7 +1036,6 @@ class FederationHandler:
         else:
             return []
 
-    @log_function
     async def on_backfill_request(
         self, origin: str, room_id: str, pdu_list: List[str], limit: int
     ) -> List[EventBase]:
@@ -1056,7 +1052,6 @@ class FederationHandler:
 
         return events
 
-    @log_function
     async def get_persisted_pdu(
         self, origin: str, event_id: str
     ) -> Optional[EventBase]:
@@ -1118,7 +1113,6 @@ class FederationHandler:
 
         return missing_events
 
-    @log_function
     async def exchange_third_party_invite(
         self, sender_user_id: str, target_user_id: str, room_id: str, signed: JsonDict
     ) -> None:
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index 11771f3c..3905f60b 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -56,7 +56,6 @@ from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.federation.federation_client import InvalidResponseError
 from synapse.logging.context import nested_logging_context, run_in_background
-from synapse.logging.utils import log_function
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.replication.http.devices import ReplicationUserDevicesResyncRestServlet
 from synapse.replication.http.federation import (
@@ -275,7 +274,6 @@ class FederationEventHandler:
 
         await self._process_received_pdu(origin, pdu, state=None)
 
-    @log_function
     async def on_send_membership_event(
         self, origin: str, event: EventBase
     ) -> Tuple[EventBase, EventContext]:
@@ -472,7 +470,6 @@ class FederationEventHandler:
 
             return await self.persist_events_and_notify(room_id, [(event, context)])
 
-    @log_function
     async def backfill(
         self, dest: str, room_id: str, limit: int, extremities: Collection[str]
     ) -> None:
diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index 601bab67..346a06ff 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -170,7 +170,7 @@ class InitialSyncHandler:
                 d["inviter"] = event.sender
 
                 invite_event = await self.store.get_event(event.event_id)
-                d["invite"] = await self._event_serializer.serialize_event(
+                d["invite"] = self._event_serializer.serialize_event(
                     invite_event,
                     time_now,
                     as_client_event=as_client_event,
@@ -222,7 +222,7 @@ class InitialSyncHandler:
 
                 d["messages"] = {
                     "chunk": (
-                        await self._event_serializer.serialize_events(
+                        self._event_serializer.serialize_events(
                             messages,
                             time_now=time_now,
                             as_client_event=as_client_event,
@@ -232,7 +232,7 @@ class InitialSyncHandler:
                     "end": await end_token.to_string(self.store),
                 }
 
-                d["state"] = await self._event_serializer.serialize_events(
+                d["state"] = self._event_serializer.serialize_events(
                     current_state.values(),
                     time_now=time_now,
                     as_client_event=as_client_event,
@@ -376,16 +376,14 @@ class InitialSyncHandler:
             "messages": {
                 "chunk": (
                     # Don't bundle aggregations as this is a deprecated API.
-                    await self._event_serializer.serialize_events(messages, time_now)
+                    self._event_serializer.serialize_events(messages, time_now)
                 ),
                 "start": await start_token.to_string(self.store),
                 "end": await end_token.to_string(self.store),
             },
             "state": (
                 # Don't bundle aggregations as this is a deprecated API.
-                await self._event_serializer.serialize_events(
-                    room_state.values(), time_now
-                )
+                self._event_serializer.serialize_events(room_state.values(), time_now)
             ),
             "presence": [],
             "receipts": [],
@@ -404,7 +402,7 @@ class InitialSyncHandler:
         # TODO: These concurrently
         time_now = self.clock.time_msec()
         # Don't bundle aggregations as this is a deprecated API.
-        state = await self._event_serializer.serialize_events(
+        state = self._event_serializer.serialize_events(
             current_state.values(), time_now
         )
 
@@ -480,7 +478,7 @@ class InitialSyncHandler:
             "messages": {
                 "chunk": (
                     # Don't bundle aggregations as this is a deprecated API.
-                    await self._event_serializer.serialize_events(messages, time_now)
+                    self._event_serializer.serialize_events(messages, time_now)
                 ),
                 "start": await start_token.to_string(self.store),
                 "end": await end_token.to_string(self.store),
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 5e3d3886..b37250aa 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -246,7 +246,7 @@ class MessageHandler:
                 room_state = room_state_events[membership_event_id]
 
         now = self.clock.time_msec()
-        events = await self._event_serializer.serialize_events(room_state.values(), now)
+        events = self._event_serializer.serialize_events(room_state.values(), now)
         return events
 
     async def get_joined_members(self, requester: Requester, room_id: str) -> dict:
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 7469cc55..973f2629 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -537,14 +537,16 @@ class PaginationHandler:
                 state_dict = await self.store.get_events(list(state_ids.values()))
                 state = state_dict.values()
 
+        aggregations = await self.store.get_bundled_aggregations(events, user_id)
+
         time_now = self.clock.time_msec()
 
         chunk = {
             "chunk": (
-                await self._event_serializer.serialize_events(
+                self._event_serializer.serialize_events(
                     events,
                     time_now,
-                    bundle_aggregations=True,
+                    bundle_aggregations=aggregations,
                     as_client_event=as_client_event,
                 )
             ),
@@ -553,7 +555,7 @@ class PaginationHandler:
         }
 
         if state:
-            chunk["state"] = await self._event_serializer.serialize_events(
+            chunk["state"] = self._event_serializer.serialize_events(
                 state, time_now, as_client_event=as_client_event
             )
 
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index c781fefb..067c43ae 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -55,7 +55,6 @@ from synapse.api.presence import UserPresenceState
 from synapse.appservice import ApplicationService
 from synapse.events.presence_router import PresenceRouter
 from synapse.logging.context import run_in_background
-from synapse.logging.utils import log_function
 from synapse.metrics import LaterGauge
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.replication.http.presence import (
@@ -1542,7 +1541,6 @@ class PresenceEventSource(EventSource[int, UserPresenceState]):
         self.clock = hs.get_clock()
         self.store = hs.get_datastore()
 
-    @log_function
     async def get_new_events(
         self,
         user: UserID,
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index b9c1cbff..f963078e 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -393,7 +393,9 @@ class RoomCreationHandler:
         user_id = requester.user.to_string()
 
         if not await self.spam_checker.user_may_create_room(user_id):
-            raise SynapseError(403, "You are not permitted to create rooms")
+            raise SynapseError(
+                403, "You are not permitted to create rooms", Codes.FORBIDDEN
+            )
 
         creation_content: JsonDict = {
             "room_version": new_room_version.identifier,
@@ -685,7 +687,9 @@ class RoomCreationHandler:
                 invite_3pid_list,
             )
         ):
-            raise SynapseError(403, "You are not permitted to create rooms")
+            raise SynapseError(
+                403, "You are not permitted to create rooms", Codes.FORBIDDEN
+            )
 
         if ratelimit:
             await self.request_ratelimiter.ratelimit(requester)
@@ -1177,6 +1181,22 @@ class RoomContextHandler:
         # `filtered` rather than the event we retrieved from the datastore.
         results["event"] = filtered[0]
 
+        # Fetch the aggregations.
+        aggregations = await self.store.get_bundled_aggregations(
+            [results["event"]], user.to_string()
+        )
+        aggregations.update(
+            await self.store.get_bundled_aggregations(
+                results["events_before"], user.to_string()
+            )
+        )
+        aggregations.update(
+            await self.store.get_bundled_aggregations(
+                results["events_after"], user.to_string()
+            )
+        )
+        results["aggregations"] = aggregations
+
         if results["events_after"]:
             last_event_id = results["events_after"][-1].event_id
         else:
diff --git a/synapse/handlers/room_summary.py b/synapse/handlers/room_summary.py
index b2cfe537..4844b69a 100644
--- a/synapse/handlers/room_summary.py
+++ b/synapse/handlers/room_summary.py
@@ -153,6 +153,9 @@ class RoomSummaryHandler:
         rooms_result: List[JsonDict] = []
         events_result: List[JsonDict] = []
 
+        if max_rooms_per_space is None or max_rooms_per_space > MAX_ROOMS_PER_SPACE:
+            max_rooms_per_space = MAX_ROOMS_PER_SPACE
+
         while room_queue and len(rooms_result) < MAX_ROOMS:
             queue_entry = room_queue.popleft()
             room_id = queue_entry.room_id
@@ -167,7 +170,7 @@ class RoomSummaryHandler:
             # The client-specified max_rooms_per_space limit doesn't apply to the
             # room_id specified in the request, so we ignore it if this is the
             # first room we are processing.
-            max_children = max_rooms_per_space if processed_rooms else None
+            max_children = max_rooms_per_space if processed_rooms else MAX_ROOMS
 
             if is_in_room:
                 room_entry = await self._summarize_local_room(
@@ -209,7 +212,7 @@ class RoomSummaryHandler:
                         # Before returning to the client, remove the allowed_room_ids
                         # and allowed_spaces keys.
                         room.pop("allowed_room_ids", None)
-                        room.pop("allowed_spaces", None)
+                        room.pop("allowed_spaces", None)  # historical
 
                         rooms_result.append(room)
                         events.extend(room_entry.children_state_events)
@@ -395,7 +398,7 @@ class RoomSummaryHandler:
                     None,
                     room_id,
                     suggested_only,
-                    # TODO Handle max children.
+                    # Do not limit the maximum children.
                     max_children=None,
                 )
 
@@ -525,6 +528,10 @@ class RoomSummaryHandler:
         rooms_result: List[JsonDict] = []
         events_result: List[JsonDict] = []
 
+        # Set a limit on the number of rooms to return.
+        if max_rooms_per_space is None or max_rooms_per_space > MAX_ROOMS_PER_SPACE:
+            max_rooms_per_space = MAX_ROOMS_PER_SPACE
+
         while room_queue and len(rooms_result) < MAX_ROOMS:
             room_id = room_queue.popleft()
             if room_id in processed_rooms:
@@ -583,7 +590,9 @@ class RoomSummaryHandler:
 
         # Iterate through each child and potentially add it, but not its children,
         # to the response.
-        for child_room in root_room_entry.children_state_events:
+        for child_room in itertools.islice(
+            root_room_entry.children_state_events, MAX_ROOMS_PER_SPACE
+        ):
             room_id = child_room.get("state_key")
             assert isinstance(room_id, str)
             # If the room is unknown, skip it.
@@ -633,8 +642,8 @@ class RoomSummaryHandler:
             suggested_only: True if only suggested children should be returned.
                 Otherwise, all children are returned.
             max_children:
-                The maximum number of children rooms to include. This is capped
-                to a server-set limit.
+                The maximum number of children rooms to include. A value of None
+                means no limit.
 
         Returns:
             A room entry if the room should be returned. None, otherwise.
@@ -656,8 +665,13 @@ class RoomSummaryHandler:
             # we only care about suggested children
             child_events = filter(_is_suggested_child_event, child_events)
 
-        if max_children is None or max_children > MAX_ROOMS_PER_SPACE:
-            max_children = MAX_ROOMS_PER_SPACE
+        # TODO max_children is legacy code for the /spaces endpoint.
+        if max_children is not None:
+            child_iter: Iterable[EventBase] = itertools.islice(
+                child_events, max_children
+            )
+        else:
+            child_iter = child_events
 
         stripped_events: List[JsonDict] = [
             {
@@ -668,7 +682,7 @@ class RoomSummaryHandler:
                 "sender": e.sender,
                 "origin_server_ts": e.origin_server_ts,
             }
-            for e in itertools.islice(child_events, max_children)
+            for e in child_iter
         ]
         return _RoomEntry(room_id, room_entry, stripped_events)
 
@@ -766,6 +780,7 @@ class RoomSummaryHandler:
         try:
             (
                 room_response,
+                children_state_events,
                 children,
                 inaccessible_children,
             ) = await self._federation_client.get_room_hierarchy(
@@ -790,7 +805,7 @@ class RoomSummaryHandler:
         }
 
         return (
-            _RoomEntry(room_id, room_response, room_response.pop("children_state", ())),
+            _RoomEntry(room_id, room_response, children_state_events),
             children_by_room_id,
             set(inaccessible_children),
         )
@@ -988,12 +1003,14 @@ class RoomSummaryHandler:
             "canonical_alias": stats["canonical_alias"],
             "num_joined_members": stats["joined_members"],
             "avatar_url": stats["avatar"],
+            # plural join_rules is a documentation error but kept for historical
+            # purposes. Should match /publicRooms.
             "join_rules": stats["join_rules"],
+            "join_rule": stats["join_rules"],
             "world_readable": (
                 stats["history_visibility"] == HistoryVisibility.WORLD_READABLE
             ),
             "guest_can_join": stats["guest_access"] == "can_join",
-            "creation_ts": create_event.origin_server_ts,
             "room_type": create_event.content.get(EventContentFields.ROOM_TYPE),
         }
 
diff --git a/synapse/handlers/search.py b/synapse/handlers/search.py
index ab7eaab2..0b153a68 100644
--- a/synapse/handlers/search.py
+++ b/synapse/handlers/search.py
@@ -420,10 +420,10 @@ class SearchHandler:
         time_now = self.clock.time_msec()
 
         for context in contexts.values():
-            context["events_before"] = await self._event_serializer.serialize_events(
+            context["events_before"] = self._event_serializer.serialize_events(
                 context["events_before"], time_now
             )
-            context["events_after"] = await self._event_serializer.serialize_events(
+            context["events_after"] = self._event_serializer.serialize_events(
                 context["events_after"], time_now
             )
 
@@ -441,9 +441,7 @@ class SearchHandler:
             results.append(
                 {
                     "rank": rank_map[e.event_id],
-                    "result": (
-                        await self._event_serializer.serialize_event(e, time_now)
-                    ),
+                    "result": self._event_serializer.serialize_event(e, time_now),
                     "context": contexts.get(e.event_id, {}),
                 }
             )
@@ -457,7 +455,7 @@ class SearchHandler:
         if state_results:
             s = {}
             for room_id, state_events in state_results.items():
-                s[room_id] = await self._event_serializer.serialize_events(
+                s[room_id] = self._event_serializer.serialize_events(
                     state_events, time_now
                 )
 
diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py
index 65c27bc6..0bb8b092 100644
--- a/synapse/handlers/sso.py
+++ b/synapse/handlers/sso.py
@@ -126,45 +126,45 @@ class SsoIdentityProvider(Protocol):
         raise NotImplementedError()
 
 
-@attr.s
+@attr.s(auto_attribs=True)
 class UserAttributes:
     # the localpart of the mxid that the mapper has assigned to the user.
     # if `None`, the mapper has not picked a userid, and the user should be prompted to
     # enter one.
-    localpart = attr.ib(type=Optional[str])
-    display_name = attr.ib(type=Optional[str], default=None)
-    emails = attr.ib(type=Collection[str], default=attr.Factory(list))
+    localpart: Optional[str]
+    display_name: Optional[str] = None
+    emails: Collection[str] = attr.Factory(list)
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class UsernameMappingSession:
     """Data we track about SSO sessions"""
 
     # A unique identifier for this SSO provider, e.g.  "oidc" or "saml".
-    auth_provider_id = attr.ib(type=str)
+    auth_provider_id: str
 
     # user ID on the IdP server
-    remote_user_id = attr.ib(type=str)
+    remote_user_id: str
 
     # attributes returned by the ID mapper
-    display_name = attr.ib(type=Optional[str])
-    emails = attr.ib(type=Collection[str])
+    display_name: Optional[str]
+    emails: Collection[str]
 
     # An optional dictionary of extra attributes to be provided to the client in the
     # login response.
-    extra_login_attributes = attr.ib(type=Optional[JsonDict])
+    extra_login_attributes: Optional[JsonDict]
 
     # where to redirect the client back to
-    client_redirect_url = attr.ib(type=str)
+    client_redirect_url: str
 
     # expiry time for the session, in milliseconds
-    expiry_time_ms = attr.ib(type=int)
+    expiry_time_ms: int
 
     # choices made by the user
-    chosen_localpart = attr.ib(type=Optional[str], default=None)
-    use_display_name = attr.ib(type=bool, default=True)
-    emails_to_use = attr.ib(type=Collection[str], default=())
-    terms_accepted_version = attr.ib(type=Optional[str], default=None)
+    chosen_localpart: Optional[str] = None
+    use_display_name: bool = True
+    emails_to_use: Collection[str] = ()
+    terms_accepted_version: Optional[str] = None
 
 
 # the HTTP cookie used to track the mapping session id
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 7baf3f19..ffc6b748 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -60,10 +60,6 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
-# Debug logger for https://github.com/matrix-org/synapse/issues/4422
-issue4422_logger = logging.getLogger("synapse.handler.sync.4422_debug")
-
-
 # Counts the number of times we returned a non-empty sync. `type` is one of
 # "initial_sync", "full_state_sync" or "incremental_sync", `lazy_loaded` is
 # "true" or "false" depending on if the request asked for lazy loaded members or
@@ -102,6 +98,9 @@ class TimelineBatch:
     prev_batch: StreamToken
     events: List[EventBase]
     limited: bool
+    # A mapping of event ID to the bundled aggregations for the above events.
+    # This is only calculated if limited is true.
+    bundled_aggregations: Optional[Dict[str, Dict[str, Any]]] = None
 
     def __bool__(self) -> bool:
         """Make the result appear empty if there are no updates. This is used
@@ -634,10 +633,19 @@ class SyncHandler:
 
             prev_batch_token = now_token.copy_and_replace("room_key", room_key)
 
+        # Don't bother to bundle aggregations if the timeline is unlimited,
+        # as clients will have all the necessary information.
+        bundled_aggregations = None
+        if limited or newly_joined_room:
+            bundled_aggregations = await self.store.get_bundled_aggregations(
+                recents, sync_config.user.to_string()
+            )
+
         return TimelineBatch(
             events=recents,
             prev_batch=prev_batch_token,
             limited=limited or newly_joined_room,
+            bundled_aggregations=bundled_aggregations,
         )
 
     async def get_state_after_event(
@@ -1161,13 +1169,8 @@ class SyncHandler:
 
         num_events = 0
 
-        # debug for https://github.com/matrix-org/synapse/issues/4422
+        # debug for https://github.com/matrix-org/synapse/issues/9424
         for joined_room in sync_result_builder.joined:
-            room_id = joined_room.room_id
-            if room_id in newly_joined_rooms:
-                issue4422_logger.debug(
-                    "Sync result for newly joined room %s: %r", room_id, joined_room
-                )
             num_events += len(joined_room.timeline.events)
 
         log_kv(
@@ -1740,18 +1743,6 @@ class SyncHandler:
                         old_mem_ev_id, allow_none=True
                     )
 
-                # debug for #4422
-                if has_join:
-                    prev_membership = None
-                    if old_mem_ev:
-                        prev_membership = old_mem_ev.membership
-                    issue4422_logger.debug(
-                        "Previous membership for room %s with join: %s (event %s)",
-                        room_id,
-                        prev_membership,
-                        old_mem_ev_id,
-                    )
-
                 if not old_mem_ev or old_mem_ev.membership != Membership.JOIN:
                     newly_joined_rooms.append(room_id)
 
@@ -1893,13 +1884,6 @@ class SyncHandler:
                     upto_token=since_token,
                 )
 
-            if newly_joined:
-                # debugging for https://github.com/matrix-org/synapse/issues/4422
-                issue4422_logger.debug(
-                    "RoomSyncResultBuilder events for newly joined room %s: %r",
-                    room_id,
-                    entry.events,
-                )
             room_entries.append(entry)
 
         return _RoomChanges(
@@ -2077,14 +2061,6 @@ class SyncHandler:
             # `_load_filtered_recents` can't find any events the user should see
             # (e.g. due to having ignored the sender of the last 50 events).
 
-            if newly_joined:
-                # debug for https://github.com/matrix-org/synapse/issues/4422
-                issue4422_logger.debug(
-                    "Timeline events after filtering in newly-joined room %s: %r",
-                    room_id,
-                    batch,
-                )
-
             # When we join the room (or the client requests full_state), we should
             # send down any existing tags. Usually the user won't have tags in a
             # newly joined room, unless either a) they've joined before or b) the
diff --git a/synapse/http/connectproxyclient.py b/synapse/http/connectproxyclient.py
index fbafffd6..203e995b 100644
--- a/synapse/http/connectproxyclient.py
+++ b/synapse/http/connectproxyclient.py
@@ -32,9 +32,9 @@ class ProxyConnectError(ConnectError):
     pass
 
 
-@attr.s
+@attr.s(auto_attribs=True)
 class ProxyCredentials:
-    username_password = attr.ib(type=bytes)
+    username_password: bytes
 
     def as_proxy_authorization_value(self) -> bytes:
         """
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index deedde0b..2e668363 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -123,37 +123,37 @@ class ByteParser(ByteWriteable, Generic[T], abc.ABC):
         pass
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class MatrixFederationRequest:
-    method = attr.ib(type=str)
+    method: str
     """HTTP method
     """
 
-    path = attr.ib(type=str)
+    path: str
     """HTTP path
     """
 
-    destination = attr.ib(type=str)
+    destination: str
     """The remote server to send the HTTP request to.
     """
 
-    json = attr.ib(default=None, type=Optional[JsonDict])
+    json: Optional[JsonDict] = None
     """JSON to send in the body.
     """
 
-    json_callback = attr.ib(default=None, type=Optional[Callable[[], JsonDict]])
+    json_callback: Optional[Callable[[], JsonDict]] = None
     """A callback to generate the JSON.
     """
 
-    query = attr.ib(default=None, type=Optional[dict])
+    query: Optional[dict] = None
     """Query arguments.
     """
 
-    txn_id = attr.ib(default=None, type=Optional[str])
+    txn_id: Optional[str] = None
     """Unique ID for this request (for logging)
     """
 
-    uri = attr.ib(init=False, type=bytes)
+    uri: bytes = attr.ib(init=False)
     """The URI of this request
     """
 
diff --git a/synapse/http/site.py b/synapse/http/site.py
index 80f7a2ff..c180a1d3 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -534,9 +534,9 @@ class XForwardedForRequest(SynapseRequest):
 
 
 @implementer(IAddress)
-@attr.s(frozen=True, slots=True)
+@attr.s(frozen=True, slots=True, auto_attribs=True)
 class _XForwardedForAddress:
-    host = attr.ib(type=str)
+    host: str
 
 
 class SynapseSite(Site):
diff --git a/synapse/logging/_remote.py b/synapse/logging/_remote.py
index 8202d049..475756f1 100644
--- a/synapse/logging/_remote.py
+++ b/synapse/logging/_remote.py
@@ -39,7 +39,7 @@ from twisted.python.failure import Failure
 logger = logging.getLogger(__name__)
 
 
-@attr.s
+@attr.s(slots=True, auto_attribs=True)
 @implementer(IPushProducer)
 class LogProducer:
     """
@@ -54,10 +54,10 @@ class LogProducer:
 
     # This is essentially ITCPTransport, but that is missing certain fields
     # (connected and registerProducer) which are part of the implementation.
-    transport = attr.ib(type=Connection)
-    _format = attr.ib(type=Callable[[logging.LogRecord], str])
-    _buffer = attr.ib(type=deque)
-    _paused = attr.ib(default=False, type=bool, init=False)
+    transport: Connection
+    _format: Callable[[logging.LogRecord], str]
+    _buffer: Deque[logging.LogRecord]
+    _paused: bool = attr.ib(default=False, init=False)
 
     def pauseProducing(self):
         self._paused = True
diff --git a/synapse/logging/context.py b/synapse/logging/context.py
index d4ee8933..c31c2960 100644
--- a/synapse/logging/context.py
+++ b/synapse/logging/context.py
@@ -193,7 +193,7 @@ class ContextResourceUsage:
         return res
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class ContextRequest:
     """
     A bundle of attributes from the SynapseRequest object.
@@ -205,15 +205,15 @@ class ContextRequest:
       their children.
     """
 
-    request_id = attr.ib(type=str)
-    ip_address = attr.ib(type=str)
-    site_tag = attr.ib(type=str)
-    requester = attr.ib(type=Optional[str])
-    authenticated_entity = attr.ib(type=Optional[str])
-    method = attr.ib(type=str)
-    url = attr.ib(type=str)
-    protocol = attr.ib(type=str)
-    user_agent = attr.ib(type=str)
+    request_id: str
+    ip_address: str
+    site_tag: str
+    requester: Optional[str]
+    authenticated_entity: Optional[str]
+    method: str
+    url: str
+    protocol: str
+    user_agent: str
 
 
 LoggingContextOrSentinel = Union["LoggingContext", "_Sentinel"]
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index 622445e9..b240d2d2 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -247,11 +247,11 @@ try:
         class BaseReporter:  # type: ignore[no-redef]
             pass
 
-    @attr.s(slots=True, frozen=True)
+    @attr.s(slots=True, frozen=True, auto_attribs=True)
     class _WrappedRustReporter(BaseReporter):
         """Wrap the reporter to ensure `report_span` never throws."""
 
-        _reporter = attr.ib(type=Reporter, default=attr.Factory(Reporter))
+        _reporter: Reporter = attr.Factory(Reporter)
 
         def set_process(self, *args, **kwargs):
             return self._reporter.set_process(*args, **kwargs)
diff --git a/synapse/logging/utils.py b/synapse/logging/utils.py
deleted file mode 100644
index 4a01b902..00000000
--- a/synapse/logging/utils.py
+++ /dev/null
@@ -1,76 +0,0 @@
-# Copyright 2014-2016 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-
-import logging
-from functools import wraps
-from inspect import getcallargs
-from typing import Callable, TypeVar, cast
-
-_TIME_FUNC_ID = 0
-
-
-def _log_debug_as_f(f, msg, msg_args):
-    name = f.__module__
-    logger = logging.getLogger(name)
-
-    if logger.isEnabledFor(logging.DEBUG):
-        lineno = f.__code__.co_firstlineno
-        pathname = f.__code__.co_filename
-
-        record = logger.makeRecord(
-            name=name,
-            level=logging.DEBUG,
-            fn=pathname,
-            lno=lineno,
-            msg=msg,
-            args=msg_args,
-            exc_info=None,
-        )
-
-        logger.handle(record)
-
-
-F = TypeVar("F", bound=Callable)
-
-
-def log_function(f: F) -> F:
-    """Function decorator that logs every call to that function."""
-    func_name = f.__name__
-
-    @wraps(f)
-    def wrapped(*args, **kwargs):
-        name = f.__module__
-        logger = logging.getLogger(name)
-        level = logging.DEBUG
-
-        if logger.isEnabledFor(level):
-            bound_args = getcallargs(f, *args, **kwargs)
-
-            def format(value):
-                r = str(value)
-                if len(r) > 50:
-                    r = r[:50] + "..."
-                return r
-
-            func_args = ["%s=%s" % (k, format(v)) for k, v in bound_args.items()]
-
-            msg_args = {"func_name": func_name, "args": ", ".join(func_args)}
-
-            _log_debug_as_f(f, "Invoked '%(func_name)s' with args: %(args)s", msg_args)
-
-        return f(*args, **kwargs)
-
-    wrapped.__name__ = func_name
-    return cast(F, wrapped)
diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index ceef57ad..9e6c1b2f 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -12,16 +12,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import functools
-import gc
 import itertools
 import logging
 import os
 import platform
 import threading
-import time
 from typing import (
-    Any,
     Callable,
     Dict,
     Generic,
@@ -34,35 +30,31 @@ from typing import (
     Type,
     TypeVar,
     Union,
-    cast,
 )
 
 import attr
 from prometheus_client import CollectorRegistry, Counter, Gauge, Histogram, Metric
 from prometheus_client.core import (
     REGISTRY,
-    CounterMetricFamily,
     GaugeHistogramMetricFamily,
     GaugeMetricFamily,
 )
 
-from twisted.internet import reactor
-from twisted.internet.base import ReactorBase
 from twisted.python.threadpool import ThreadPool
 
-import synapse
+import synapse.metrics._reactor_metrics
 from synapse.metrics._exposition import (
     MetricsResource,
     generate_latest,
     start_http_server,
 )
+from synapse.metrics._gc import MIN_TIME_BETWEEN_GCS, install_gc_manager
 from synapse.util.versionstring import get_version_string
 
 logger = logging.getLogger(__name__)
 
 METRICS_PREFIX = "/_synapse/metrics"
 
-running_on_pypy = platform.python_implementation() == "PyPy"
 all_gauges: "Dict[str, Union[LaterGauge, InFlightGauge]]" = {}
 
 HAVE_PROC_SELF_STAT = os.path.exists("/proc/self/stat")
@@ -76,19 +68,17 @@ class RegistryProxy:
                 yield metric
 
 
-@attr.s(slots=True, hash=True)
+@attr.s(slots=True, hash=True, auto_attribs=True)
 class LaterGauge:
 
-    name = attr.ib(type=str)
-    desc = attr.ib(type=str)
-    labels = attr.ib(hash=False, type=Optional[Iterable[str]])
+    name: str
+    desc: str
+    labels: Optional[Iterable[str]] = attr.ib(hash=False)
     # callback: should either return a value (if there are no labels for this metric),
     # or dict mapping from a label tuple to a value
-    caller = attr.ib(
-        type=Callable[
-            [], Union[Mapping[Tuple[str, ...], Union[int, float]], Union[int, float]]
-        ]
-    )
+    caller: Callable[
+        [], Union[Mapping[Tuple[str, ...], Union[int, float]], Union[int, float]]
+    ]
 
     def collect(self) -> Iterable[Metric]:
 
@@ -157,7 +147,9 @@ class InFlightGauge(Generic[MetricsEntry]):
         # Create a class which have the sub_metrics values as attributes, which
         # default to 0 on initialization. Used to pass to registered callbacks.
         self._metrics_class: Type[MetricsEntry] = attr.make_class(
-            "_MetricsEntry", attrs={x: attr.ib(0) for x in sub_metrics}, slots=True
+            "_MetricsEntry",
+            attrs={x: attr.ib(default=0) for x in sub_metrics},
+            slots=True,
         )
 
         # Counts number of in flight blocks for a given set of label values
@@ -369,136 +361,6 @@ class CPUMetrics:
 
 REGISTRY.register(CPUMetrics())
 
-#
-# Python GC metrics
-#
-
-gc_unreachable = Gauge("python_gc_unreachable_total", "Unreachable GC objects", ["gen"])
-gc_time = Histogram(
-    "python_gc_time",
-    "Time taken to GC (sec)",
-    ["gen"],
-    buckets=[
-        0.0025,
-        0.005,
-        0.01,
-        0.025,
-        0.05,
-        0.10,
-        0.25,
-        0.50,
-        1.00,
-        2.50,
-        5.00,
-        7.50,
-        15.00,
-        30.00,
-        45.00,
-        60.00,
-    ],
-)
-
-
-class GCCounts:
-    def collect(self) -> Iterable[Metric]:
-        cm = GaugeMetricFamily("python_gc_counts", "GC object counts", labels=["gen"])
-        for n, m in enumerate(gc.get_count()):
-            cm.add_metric([str(n)], m)
-
-        yield cm
-
-
-if not running_on_pypy:
-    REGISTRY.register(GCCounts())
-
-
-#
-# PyPy GC / memory metrics
-#
-
-
-class PyPyGCStats:
-    def collect(self) -> Iterable[Metric]:
-
-        # @stats is a pretty-printer object with __str__() returning a nice table,
-        # plus some fields that contain data from that table.
-        # unfortunately, fields are pretty-printed themselves (i. e. '4.5MB').
-        stats = gc.get_stats(memory_pressure=False)  # type: ignore
-        # @s contains same fields as @stats, but as actual integers.
-        s = stats._s  # type: ignore
-
-        # also note that field naming is completely braindead
-        # and only vaguely correlates with the pretty-printed table.
-        # >>>> gc.get_stats(False)
-        # Total memory consumed:
-        #     GC used:            8.7MB (peak: 39.0MB)        # s.total_gc_memory, s.peak_memory
-        #        in arenas:            3.0MB                  # s.total_arena_memory
-        #        rawmalloced:          1.7MB                  # s.total_rawmalloced_memory
-        #        nursery:              4.0MB                  # s.nursery_size
-        #     raw assembler used: 31.0kB                      # s.jit_backend_used
-        #     -----------------------------
-        #     Total:              8.8MB                       # stats.memory_used_sum
-        #
-        #     Total memory allocated:
-        #     GC allocated:            38.7MB (peak: 41.1MB)  # s.total_allocated_memory, s.peak_allocated_memory
-        #        in arenas:            30.9MB                 # s.peak_arena_memory
-        #        rawmalloced:          4.1MB                  # s.peak_rawmalloced_memory
-        #        nursery:              4.0MB                  # s.nursery_size
-        #     raw assembler allocated: 1.0MB                  # s.jit_backend_allocated
-        #     -----------------------------
-        #     Total:                   39.7MB                 # stats.memory_allocated_sum
-        #
-        #     Total time spent in GC:  0.073                  # s.total_gc_time
-
-        pypy_gc_time = CounterMetricFamily(
-            "pypy_gc_time_seconds_total",
-            "Total time spent in PyPy GC",
-            labels=[],
-        )
-        pypy_gc_time.add_metric([], s.total_gc_time / 1000)
-        yield pypy_gc_time
-
-        pypy_mem = GaugeMetricFamily(
-            "pypy_memory_bytes",
-            "Memory tracked by PyPy allocator",
-            labels=["state", "class", "kind"],
-        )
-        # memory used by JIT assembler
-        pypy_mem.add_metric(["used", "", "jit"], s.jit_backend_used)
-        pypy_mem.add_metric(["allocated", "", "jit"], s.jit_backend_allocated)
-        # memory used by GCed objects
-        pypy_mem.add_metric(["used", "", "arenas"], s.total_arena_memory)
-        pypy_mem.add_metric(["allocated", "", "arenas"], s.peak_arena_memory)
-        pypy_mem.add_metric(["used", "", "rawmalloced"], s.total_rawmalloced_memory)
-        pypy_mem.add_metric(["allocated", "", "rawmalloced"], s.peak_rawmalloced_memory)
-        pypy_mem.add_metric(["used", "", "nursery"], s.nursery_size)
-        pypy_mem.add_metric(["allocated", "", "nursery"], s.nursery_size)
-        # totals
-        pypy_mem.add_metric(["used", "totals", "gc"], s.total_gc_memory)
-        pypy_mem.add_metric(["allocated", "totals", "gc"], s.total_allocated_memory)
-        pypy_mem.add_metric(["used", "totals", "gc_peak"], s.peak_memory)
-        pypy_mem.add_metric(["allocated", "totals", "gc_peak"], s.peak_allocated_memory)
-        yield pypy_mem
-
-
-if running_on_pypy:
-    REGISTRY.register(PyPyGCStats())
-
-
-#
-# Twisted reactor metrics
-#
-
-tick_time = Histogram(
-    "python_twisted_reactor_tick_time",
-    "Tick time of the Twisted reactor (sec)",
-    buckets=[0.001, 0.002, 0.005, 0.01, 0.025, 0.05, 0.1, 0.2, 0.5, 1, 2, 5],
-)
-pending_calls_metric = Histogram(
-    "python_twisted_reactor_pending_calls",
-    "Pending calls",
-    buckets=[1, 2, 5, 10, 25, 50, 100, 250, 500, 1000],
-)
 
 #
 # Federation Metrics
@@ -551,8 +413,6 @@ build_info.labels(
     " ".join([platform.system(), platform.release()]),
 ).set(1)
 
-last_ticked = time.time()
-
 # 3PID send info
 threepid_send_requests = Histogram(
     "synapse_threepid_send_requests_with_tries",
@@ -600,116 +460,6 @@ def register_threadpool(name: str, threadpool: ThreadPool) -> None:
     )
 
 
-class ReactorLastSeenMetric:
-    def collect(self) -> Iterable[Metric]:
-        cm = GaugeMetricFamily(
-            "python_twisted_reactor_last_seen",
-            "Seconds since the Twisted reactor was last seen",
-        )
-        cm.add_metric([], time.time() - last_ticked)
-        yield cm
-
-
-REGISTRY.register(ReactorLastSeenMetric())
-
-# The minimum time in seconds between GCs for each generation, regardless of the current GC
-# thresholds and counts.
-MIN_TIME_BETWEEN_GCS = (1.0, 10.0, 30.0)
-
-# The time (in seconds since the epoch) of the last time we did a GC for each generation.
-_last_gc = [0.0, 0.0, 0.0]
-
-
-F = TypeVar("F", bound=Callable[..., Any])
-
-
-def runUntilCurrentTimer(reactor: ReactorBase, func: F) -> F:
-    @functools.wraps(func)
-    def f(*args: Any, **kwargs: Any) -> Any:
-        now = reactor.seconds()
-        num_pending = 0
-
-        # _newTimedCalls is one long list of *all* pending calls. Below loop
-        # is based off of impl of reactor.runUntilCurrent
-        for delayed_call in reactor._newTimedCalls:
-            if delayed_call.time > now:
-                break
-
-            if delayed_call.delayed_time > 0:
-                continue
-
-            num_pending += 1
-
-        num_pending += len(reactor.threadCallQueue)
-        start = time.time()
-        ret = func(*args, **kwargs)
-        end = time.time()
-
-        # record the amount of wallclock time spent running pending calls.
-        # This is a proxy for the actual amount of time between reactor polls,
-        # since about 25% of time is actually spent running things triggered by
-        # I/O events, but that is harder to capture without rewriting half the
-        # reactor.
-        tick_time.observe(end - start)
-        pending_calls_metric.observe(num_pending)
-
-        # Update the time we last ticked, for the metric to test whether
-        # Synapse's reactor has frozen
-        global last_ticked
-        last_ticked = end
-
-        if running_on_pypy:
-            return ret
-
-        # Check if we need to do a manual GC (since its been disabled), and do
-        # one if necessary. Note we go in reverse order as e.g. a gen 1 GC may
-        # promote an object into gen 2, and we don't want to handle the same
-        # object multiple times.
-        threshold = gc.get_threshold()
-        counts = gc.get_count()
-        for i in (2, 1, 0):
-            # We check if we need to do one based on a straightforward
-            # comparison between the threshold and count. We also do an extra
-            # check to make sure that we don't a GC too often.
-            if threshold[i] < counts[i] and MIN_TIME_BETWEEN_GCS[i] < end - _last_gc[i]:
-                if i == 0:
-                    logger.debug("Collecting gc %d", i)
-                else:
-                    logger.info("Collecting gc %d", i)
-
-                start = time.time()
-                unreachable = gc.collect(i)
-                end = time.time()
-
-                _last_gc[i] = end
-
-                gc_time.labels(i).observe(end - start)
-                gc_unreachable.labels(i).set(unreachable)
-
-        return ret
-
-    return cast(F, f)
-
-
-try:
-    # Ensure the reactor has all the attributes we expect
-    reactor.seconds  # type: ignore
-    reactor.runUntilCurrent  # type: ignore
-    reactor._newTimedCalls  # type: ignore
-    reactor.threadCallQueue  # type: ignore
-
-    # runUntilCurrent is called when we have pending calls. It is called once
-    # per iteratation after fd polling.
-    reactor.runUntilCurrent = runUntilCurrentTimer(reactor, reactor.runUntilCurrent)  # type: ignore
-
-    # We manually run the GC each reactor tick so that we can get some metrics
-    # about time spent doing GC,
-    if not running_on_pypy:
-        gc.disable()
-except AttributeError:
-    pass
-
-
 __all__ = [
     "MetricsResource",
     "generate_latest",
@@ -717,4 +467,6 @@ __all__ = [
     "LaterGauge",
     "InFlightGauge",
     "GaugeBucketCollector",
+    "MIN_TIME_BETWEEN_GCS",
+    "install_gc_manager",
 ]
diff --git a/synapse/metrics/_gc.py b/synapse/metrics/_gc.py
new file mode 100644
index 00000000..2bc909ef
--- /dev/null
+++ b/synapse/metrics/_gc.py
@@ -0,0 +1,203 @@
+# Copyright 2015-2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import gc
+import logging
+import platform
+import time
+from typing import Iterable
+
+from prometheus_client.core import (
+    REGISTRY,
+    CounterMetricFamily,
+    Gauge,
+    GaugeMetricFamily,
+    Histogram,
+    Metric,
+)
+
+from twisted.internet import task
+
+"""Prometheus metrics for garbage collection"""
+
+
+logger = logging.getLogger(__name__)
+
+# The minimum time in seconds between GCs for each generation, regardless of the current GC
+# thresholds and counts.
+MIN_TIME_BETWEEN_GCS = (1.0, 10.0, 30.0)
+
+running_on_pypy = platform.python_implementation() == "PyPy"
+
+#
+# Python GC metrics
+#
+
+gc_unreachable = Gauge("python_gc_unreachable_total", "Unreachable GC objects", ["gen"])
+gc_time = Histogram(
+    "python_gc_time",
+    "Time taken to GC (sec)",
+    ["gen"],
+    buckets=[
+        0.0025,
+        0.005,
+        0.01,
+        0.025,
+        0.05,
+        0.10,
+        0.25,
+        0.50,
+        1.00,
+        2.50,
+        5.00,
+        7.50,
+        15.00,
+        30.00,
+        45.00,
+        60.00,
+    ],
+)
+
+
+class GCCounts:
+    def collect(self) -> Iterable[Metric]:
+        cm = GaugeMetricFamily("python_gc_counts", "GC object counts", labels=["gen"])
+        for n, m in enumerate(gc.get_count()):
+            cm.add_metric([str(n)], m)
+
+        yield cm
+
+
+def install_gc_manager() -> None:
+    """Disable automatic GC, and replace it with a task that runs every 100ms
+
+    This means that (a) we can limit how often GC runs; (b) we can get some metrics
+    about GC activity.
+
+    It does nothing on PyPy.
+    """
+
+    if running_on_pypy:
+        return
+
+    REGISTRY.register(GCCounts())
+
+    gc.disable()
+
+    # The time (in seconds since the epoch) of the last time we did a GC for each generation.
+    _last_gc = [0.0, 0.0, 0.0]
+
+    def _maybe_gc() -> None:
+        # Check if we need to do a manual GC (since its been disabled), and do
+        # one if necessary. Note we go in reverse order as e.g. a gen 1 GC may
+        # promote an object into gen 2, and we don't want to handle the same
+        # object multiple times.
+        threshold = gc.get_threshold()
+        counts = gc.get_count()
+        end = time.time()
+        for i in (2, 1, 0):
+            # We check if we need to do one based on a straightforward
+            # comparison between the threshold and count. We also do an extra
+            # check to make sure that we don't a GC too often.
+            if threshold[i] < counts[i] and MIN_TIME_BETWEEN_GCS[i] < end - _last_gc[i]:
+                if i == 0:
+                    logger.debug("Collecting gc %d", i)
+                else:
+                    logger.info("Collecting gc %d", i)
+
+                start = time.time()
+                unreachable = gc.collect(i)
+                end = time.time()
+
+                _last_gc[i] = end
+
+                gc_time.labels(i).observe(end - start)
+                gc_unreachable.labels(i).set(unreachable)
+
+    gc_task = task.LoopingCall(_maybe_gc)
+    gc_task.start(0.1)
+
+
+#
+# PyPy GC / memory metrics
+#
+
+
+class PyPyGCStats:
+    def collect(self) -> Iterable[Metric]:
+
+        # @stats is a pretty-printer object with __str__() returning a nice table,
+        # plus some fields that contain data from that table.
+        # unfortunately, fields are pretty-printed themselves (i. e. '4.5MB').
+        stats = gc.get_stats(memory_pressure=False)  # type: ignore
+        # @s contains same fields as @stats, but as actual integers.
+        s = stats._s  # type: ignore
+
+        # also note that field naming is completely braindead
+        # and only vaguely correlates with the pretty-printed table.
+        # >>>> gc.get_stats(False)
+        # Total memory consumed:
+        #     GC used:            8.7MB (peak: 39.0MB)        # s.total_gc_memory, s.peak_memory
+        #        in arenas:            3.0MB                  # s.total_arena_memory
+        #        rawmalloced:          1.7MB                  # s.total_rawmalloced_memory
+        #        nursery:              4.0MB                  # s.nursery_size
+        #     raw assembler used: 31.0kB                      # s.jit_backend_used
+        #     -----------------------------
+        #     Total:              8.8MB                       # stats.memory_used_sum
+        #
+        #     Total memory allocated:
+        #     GC allocated:            38.7MB (peak: 41.1MB)  # s.total_allocated_memory, s.peak_allocated_memory
+        #        in arenas:            30.9MB                 # s.peak_arena_memory
+        #        rawmalloced:          4.1MB                  # s.peak_rawmalloced_memory
+        #        nursery:              4.0MB                  # s.nursery_size
+        #     raw assembler allocated: 1.0MB                  # s.jit_backend_allocated
+        #     -----------------------------
+        #     Total:                   39.7MB                 # stats.memory_allocated_sum
+        #
+        #     Total time spent in GC:  0.073                  # s.total_gc_time
+
+        pypy_gc_time = CounterMetricFamily(
+            "pypy_gc_time_seconds_total",
+            "Total time spent in PyPy GC",
+            labels=[],
+        )
+        pypy_gc_time.add_metric([], s.total_gc_time / 1000)
+        yield pypy_gc_time
+
+        pypy_mem = GaugeMetricFamily(
+            "pypy_memory_bytes",
+            "Memory tracked by PyPy allocator",
+            labels=["state", "class", "kind"],
+        )
+        # memory used by JIT assembler
+        pypy_mem.add_metric(["used", "", "jit"], s.jit_backend_used)
+        pypy_mem.add_metric(["allocated", "", "jit"], s.jit_backend_allocated)
+        # memory used by GCed objects
+        pypy_mem.add_metric(["used", "", "arenas"], s.total_arena_memory)
+        pypy_mem.add_metric(["allocated", "", "arenas"], s.peak_arena_memory)
+        pypy_mem.add_metric(["used", "", "rawmalloced"], s.total_rawmalloced_memory)
+        pypy_mem.add_metric(["allocated", "", "rawmalloced"], s.peak_rawmalloced_memory)
+        pypy_mem.add_metric(["used", "", "nursery"], s.nursery_size)
+        pypy_mem.add_metric(["allocated", "", "nursery"], s.nursery_size)
+        # totals
+        pypy_mem.add_metric(["used", "totals", "gc"], s.total_gc_memory)
+        pypy_mem.add_metric(["allocated", "totals", "gc"], s.total_allocated_memory)
+        pypy_mem.add_metric(["used", "totals", "gc_peak"], s.peak_memory)
+        pypy_mem.add_metric(["allocated", "totals", "gc_peak"], s.peak_allocated_memory)
+        yield pypy_mem
+
+
+if running_on_pypy:
+    REGISTRY.register(PyPyGCStats())
diff --git a/synapse/metrics/_reactor_metrics.py b/synapse/metrics/_reactor_metrics.py
new file mode 100644
index 00000000..f38f7983
--- /dev/null
+++ b/synapse/metrics/_reactor_metrics.py
@@ -0,0 +1,83 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import select
+import time
+from typing import Any, Iterable, List, Tuple
+
+from prometheus_client import Histogram, Metric
+from prometheus_client.core import REGISTRY, GaugeMetricFamily
+
+from twisted.internet import reactor
+
+#
+# Twisted reactor metrics
+#
+
+tick_time = Histogram(
+    "python_twisted_reactor_tick_time",
+    "Tick time of the Twisted reactor (sec)",
+    buckets=[0.001, 0.002, 0.005, 0.01, 0.025, 0.05, 0.1, 0.2, 0.5, 1, 2, 5],
+)
+
+
+class EpollWrapper:
+    """a wrapper for an epoll object which records the time between polls"""
+
+    def __init__(self, poller: "select.epoll"):  # type: ignore[name-defined]
+        self.last_polled = time.time()
+        self._poller = poller
+
+    def poll(self, *args, **kwargs) -> List[Tuple[int, int]]:  # type: ignore[no-untyped-def]
+        # record the time since poll() was last called. This gives a good proxy for
+        # how long it takes to run everything in the reactor - ie, how long anything
+        # waiting for the next tick will have to wait.
+        tick_time.observe(time.time() - self.last_polled)
+
+        ret = self._poller.poll(*args, **kwargs)
+
+        self.last_polled = time.time()
+        return ret
+
+    def __getattr__(self, item: str) -> Any:
+        return getattr(self._poller, item)
+
+
+class ReactorLastSeenMetric:
+    def __init__(self, epoll_wrapper: EpollWrapper):
+        self._epoll_wrapper = epoll_wrapper
+
+    def collect(self) -> Iterable[Metric]:
+        cm = GaugeMetricFamily(
+            "python_twisted_reactor_last_seen",
+            "Seconds since the Twisted reactor was last seen",
+        )
+        cm.add_metric([], time.time() - self._epoll_wrapper.last_polled)
+        yield cm
+
+
+try:
+    # if the reactor has a `_poller` attribute, which is an `epoll` object
+    # (ie, it's an EPollReactor), we wrap the `epoll` with a thing that will
+    # measure the time between ticks
+    from select import epoll  # type: ignore[attr-defined]
+
+    poller = reactor._poller  # type: ignore[attr-defined]
+except (AttributeError, ImportError):
+    pass
+else:
+    if isinstance(poller, epoll):
+        poller = EpollWrapper(poller)
+        reactor._poller = poller  # type: ignore[attr-defined]
+        REGISTRY.register(ReactorLastSeenMetric(poller))
diff --git a/synapse/notifier.py b/synapse/notifier.py
index bbabdb05..632b2245 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -40,7 +40,6 @@ from synapse.handlers.presence import format_user_presence_state
 from synapse.logging import issue9533_logger
 from synapse.logging.context import PreserveLoggingContext
 from synapse.logging.opentracing import log_kv, start_active_span
-from synapse.logging.utils import log_function
 from synapse.metrics import LaterGauge
 from synapse.streams.config import PaginationConfig
 from synapse.types import (
@@ -193,15 +192,15 @@ class EventStreamResult:
         return bool(self.events)
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class _PendingRoomEventEntry:
-    event_pos = attr.ib(type=PersistedEventPosition)
-    extra_users = attr.ib(type=Collection[UserID])
+    event_pos: PersistedEventPosition
+    extra_users: Collection[UserID]
 
-    room_id = attr.ib(type=str)
-    type = attr.ib(type=str)
-    state_key = attr.ib(type=Optional[str])
-    membership = attr.ib(type=Optional[str])
+    room_id: str
+    type: str
+    state_key: Optional[str]
+    membership: Optional[str]
 
 
 class Notifier:
@@ -686,7 +685,6 @@ class Notifier:
         else:
             return False
 
-    @log_function
     def remove_expired_streams(self) -> None:
         time_now_ms = self.clock.time_msec()
         expired_streams = []
@@ -700,7 +698,6 @@ class Notifier:
         for expired_stream in expired_streams:
             expired_stream.remove(self)
 
-    @log_function
     def _register_with_keys(self, user_stream: _NotifierUserStream):
         self.user_to_user_stream[user_stream.user_id] = user_stream
 
diff --git a/synapse/push/__init__.py b/synapse/push/__init__.py
index 820f6f3f..5176a1c1 100644
--- a/synapse/push/__init__.py
+++ b/synapse/push/__init__.py
@@ -23,25 +23,25 @@ if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class PusherConfig:
     """Parameters necessary to configure a pusher."""
 
-    id = attr.ib(type=Optional[str])
-    user_name = attr.ib(type=str)
-    access_token = attr.ib(type=Optional[int])
-    profile_tag = attr.ib(type=str)
-    kind = attr.ib(type=str)
-    app_id = attr.ib(type=str)
-    app_display_name = attr.ib(type=str)
-    device_display_name = attr.ib(type=str)
-    pushkey = attr.ib(type=str)
-    ts = attr.ib(type=int)
-    lang = attr.ib(type=Optional[str])
-    data = attr.ib(type=Optional[JsonDict])
-    last_stream_ordering = attr.ib(type=int)
-    last_success = attr.ib(type=Optional[int])
-    failing_since = attr.ib(type=Optional[int])
+    id: Optional[str]
+    user_name: str
+    access_token: Optional[int]
+    profile_tag: str
+    kind: str
+    app_id: str
+    app_display_name: str
+    device_display_name: str
+    pushkey: str
+    ts: int
+    lang: Optional[str]
+    data: Optional[JsonDict]
+    last_stream_ordering: int
+    last_success: Optional[int]
+    failing_since: Optional[int]
 
     def as_dict(self) -> Dict[str, Any]:
         """Information that can be retrieved about a pusher after creation."""
@@ -57,12 +57,12 @@ class PusherConfig:
         }
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class ThrottleParams:
     """Parameters for controlling the rate of sending pushes via email."""
 
-    last_sent_ts = attr.ib(type=int)
-    throttle_ms = attr.ib(type=int)
+    last_sent_ts: int
+    throttle_ms: int
 
 
 class Pusher(metaclass=abc.ABCMeta):
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 009d8e77..bee66089 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -298,7 +298,7 @@ RulesByUser = Dict[str, List[Rule]]
 StateGroup = Union[object, int]
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class RulesForRoomData:
     """The data stored in the cache by `RulesForRoom`.
 
@@ -307,29 +307,29 @@ class RulesForRoomData:
     """
 
     # event_id -> (user_id, state)
-    member_map = attr.ib(type=MemberMap, factory=dict)
+    member_map: MemberMap = attr.Factory(dict)
     # user_id -> rules
-    rules_by_user = attr.ib(type=RulesByUser, factory=dict)
+    rules_by_user: RulesByUser = attr.Factory(dict)
 
     # The last state group we updated the caches for. If the state_group of
     # a new event comes along, we know that we can just return the cached
     # result.
     # On invalidation of the rules themselves (if the user changes them),
     # we invalidate everything and set state_group to `object()`
-    state_group = attr.ib(type=StateGroup, factory=object)
+    state_group: StateGroup = attr.Factory(object)
 
     # A sequence number to keep track of when we're allowed to update the
     # cache. We bump the sequence number when we invalidate the cache. If
     # the sequence number changes while we're calculating stuff we should
     # not update the cache with it.
-    sequence = attr.ib(type=int, default=0)
+    sequence: int = 0
 
     # A cache of user_ids that we *know* aren't interesting, e.g. user_ids
     # owned by AS's, or remote users, etc. (I.e. users we will never need to
     # calculate push for)
     # These never need to be invalidated as we will never set up push for
     # them.
-    uninteresting_user_set = attr.ib(type=Set[str], factory=set)
+    uninteresting_user_set: Set[str] = attr.Factory(set)
 
 
 class RulesForRoom:
@@ -553,7 +553,7 @@ class RulesForRoom:
             self.data.state_group = state_group
 
 
-@attr.attrs(slots=True, frozen=True)
+@attr.attrs(slots=True, frozen=True, auto_attribs=True)
 class _Invalidation:
     # _Invalidation is passed as an `on_invalidate` callback to bulk_get_push_rules,
     # which means that it it is stored on the bulk_get_push_rules cache entry. In order
@@ -564,8 +564,8 @@ class _Invalidation:
     # attrs provides suitable __hash__ and __eq__ methods, provided we remember to
     # set `frozen=True`.
 
-    cache = attr.ib(type=LruCache)
-    room_id = attr.ib(type=str)
+    cache: LruCache
+    room_id: str
 
     def __call__(self) -> None:
         rules_data = self.cache.get(self.room_id, None, update_metrics=False)
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index ff904c2b..dadfc574 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -178,7 +178,7 @@ class Mailer:
         await self.send_email(
             email_address,
             self.email_subjects.email_validation
-            % {"server_name": self.hs.config.server.server_name},
+            % {"server_name": self.hs.config.server.server_name, "app": self.app_name},
             template_vars,
         )
 
@@ -209,7 +209,7 @@ class Mailer:
         await self.send_email(
             email_address,
             self.email_subjects.email_validation
-            % {"server_name": self.hs.config.server.server_name},
+            % {"server_name": self.hs.config.server.server_name, "app": self.app_name},
             template_vars,
         )
 
diff --git a/synapse/replication/tcp/streams/events.py b/synapse/replication/tcp/streams/events.py
index a390cfcb..4f4f1ad4 100644
--- a/synapse/replication/tcp/streams/events.py
+++ b/synapse/replication/tcp/streams/events.py
@@ -50,12 +50,12 @@ data part are:
 """
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class EventsStreamRow:
     """A parsed row from the events replication stream"""
 
-    type = attr.ib()  # str: the TypeId of one of the *EventsStreamRows
-    data = attr.ib()  # BaseEventsStreamRow
+    type: str  # the TypeId of one of the *EventsStreamRows
+    data: "BaseEventsStreamRow"
 
 
 class BaseEventsStreamRow:
@@ -79,28 +79,28 @@ class BaseEventsStreamRow:
         return cls(*data)
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class EventsStreamEventRow(BaseEventsStreamRow):
     TypeId = "ev"
 
-    event_id = attr.ib(type=str)
-    room_id = attr.ib(type=str)
-    type = attr.ib(type=str)
-    state_key = attr.ib(type=Optional[str])
-    redacts = attr.ib(type=Optional[str])
-    relates_to = attr.ib(type=Optional[str])
-    membership = attr.ib(type=Optional[str])
-    rejected = attr.ib(type=bool)
+    event_id: str
+    room_id: str
+    type: str
+    state_key: Optional[str]
+    redacts: Optional[str]
+    relates_to: Optional[str]
+    membership: Optional[str]
+    rejected: bool
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class EventsStreamCurrentStateRow(BaseEventsStreamRow):
     TypeId = "state"
 
-    room_id = attr.ib()  # str
-    type = attr.ib()  # str
-    state_key = attr.ib()  # str
-    event_id = attr.ib()  # str, optional
+    room_id: str
+    type: str
+    state_key: str
+    event_id: Optional[str]
 
 
 _EventRows: Tuple[Type[BaseEventsStreamRow], ...] = (
diff --git a/synapse/rest/admin/background_updates.py b/synapse/rest/admin/background_updates.py
index 6ec00ce0..e9bce22a 100644
--- a/synapse/rest/admin/background_updates.py
+++ b/synapse/rest/admin/background_updates.py
@@ -123,34 +123,25 @@ class BackgroundUpdateStartJobRestServlet(RestServlet):
         job_name = body["job_name"]
 
         if job_name == "populate_stats_process_rooms":
-            jobs = [
-                {
-                    "update_name": "populate_stats_process_rooms",
-                    "progress_json": "{}",
-                },
-            ]
+            jobs = [("populate_stats_process_rooms", "{}", "")]
         elif job_name == "regenerate_directory":
             jobs = [
-                {
-                    "update_name": "populate_user_directory_createtables",
-                    "progress_json": "{}",
-                    "depends_on": "",
-                },
-                {
-                    "update_name": "populate_user_directory_process_rooms",
-                    "progress_json": "{}",
-                    "depends_on": "populate_user_directory_createtables",
-                },
-                {
-                    "update_name": "populate_user_directory_process_users",
-                    "progress_json": "{}",
-                    "depends_on": "populate_user_directory_process_rooms",
-                },
-                {
-                    "update_name": "populate_user_directory_cleanup",
-                    "progress_json": "{}",
-                    "depends_on": "populate_user_directory_process_users",
-                },
+                ("populate_user_directory_createtables", "{}", ""),
+                (
+                    "populate_user_directory_process_rooms",
+                    "{}",
+                    "populate_user_directory_createtables",
+                ),
+                (
+                    "populate_user_directory_process_users",
+                    "{}",
+                    "populate_user_directory_process_rooms",
+                ),
+                (
+                    "populate_user_directory_cleanup",
+                    "{}",
+                    "populate_user_directory_process_users",
+                ),
             ]
         else:
             raise SynapseError(HTTPStatus.BAD_REQUEST, "Invalid job_name")
@@ -158,6 +149,7 @@ class BackgroundUpdateStartJobRestServlet(RestServlet):
         try:
             await self._store.db_pool.simple_insert_many(
                 table="background_updates",
+                keys=("update_name", "progress_json", "depends_on"),
                 values=jobs,
                 desc=f"admin_api_run_{job_name}",
             )
diff --git a/synapse/rest/admin/federation.py b/synapse/rest/admin/federation.py
index 50d88c91..8cd3fa18 100644
--- a/synapse/rest/admin/federation.py
+++ b/synapse/rest/admin/federation.py
@@ -111,25 +111,37 @@ class DestinationsRestServlet(RestServlet):
     ) -> Tuple[int, JsonDict]:
         await assert_requester_is_admin(self._auth, request)
 
+        if not await self._store.is_destination_known(destination):
+            raise NotFoundError("Unknown destination")
+
         destination_retry_timings = await self._store.get_destination_retry_timings(
             destination
         )
 
-        if not destination_retry_timings:
-            raise NotFoundError("Unknown destination")
-
         last_successful_stream_ordering = (
             await self._store.get_destination_last_successful_stream_ordering(
                 destination
             )
         )
 
-        response = {
+        response: JsonDict = {
             "destination": destination,
-            "failure_ts": destination_retry_timings.failure_ts,
-            "retry_last_ts": destination_retry_timings.retry_last_ts,
-            "retry_interval": destination_retry_timings.retry_interval,
             "last_successful_stream_ordering": last_successful_stream_ordering,
         }
 
+        if destination_retry_timings:
+            response = {
+                **response,
+                "failure_ts": destination_retry_timings.failure_ts,
+                "retry_last_ts": destination_retry_timings.retry_last_ts,
+                "retry_interval": destination_retry_timings.retry_interval,
+            }
+        else:
+            response = {
+                **response,
+                "failure_ts": None,
+                "retry_last_ts": 0,
+                "retry_interval": 0,
+            }
+
         return HTTPStatus.OK, response
diff --git a/synapse/rest/admin/media.py b/synapse/rest/admin/media.py
index 7236e402..299f5c9e 100644
--- a/synapse/rest/admin/media.py
+++ b/synapse/rest/admin/media.py
@@ -466,7 +466,7 @@ class UserMediaRestServlet(RestServlet):
         )
 
         deleted_media, total = await self.media_repository.delete_local_media_ids(
-            ([row["media_id"] for row in media])
+            [row["media_id"] for row in media]
         )
 
         return HTTPStatus.OK, {"deleted_media": deleted_media, "total": total}
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index 6030373e..efe25fe7 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -424,7 +424,7 @@ class RoomStateRestServlet(RestServlet):
         event_ids = await self.store.get_current_state_ids(room_id)
         events = await self.store.get_events(event_ids.values())
         now = self.clock.time_msec()
-        room_state = await self._event_serializer.serialize_events(events.values(), now)
+        room_state = self._event_serializer.serialize_events(events.values(), now)
         ret = {"state": room_state}
 
         return HTTPStatus.OK, ret
@@ -744,22 +744,17 @@ class RoomEventContextServlet(RestServlet):
             )
 
         time_now = self.clock.time_msec()
-        results["events_before"] = await self._event_serializer.serialize_events(
-            results["events_before"],
-            time_now,
-            bundle_aggregations=True,
+        aggregations = results.pop("aggregations", None)
+        results["events_before"] = self._event_serializer.serialize_events(
+            results["events_before"], time_now, bundle_aggregations=aggregations
         )
-        results["event"] = await self._event_serializer.serialize_event(
-            results["event"],
-            time_now,
-            bundle_aggregations=True,
+        results["event"] = self._event_serializer.serialize_event(
+            results["event"], time_now, bundle_aggregations=aggregations
         )
-        results["events_after"] = await self._event_serializer.serialize_events(
-            results["events_after"],
-            time_now,
-            bundle_aggregations=True,
+        results["events_after"] = self._event_serializer.serialize_events(
+            results["events_after"], time_now, bundle_aggregations=aggregations
         )
-        results["state"] = await self._event_serializer.serialize_events(
+        results["state"] = self._event_serializer.serialize_events(
             results["state"], time_now
         )
 
diff --git a/synapse/rest/admin/users.py b/synapse/rest/admin/users.py
index 78e795c3..c2617ee3 100644
--- a/synapse/rest/admin/users.py
+++ b/synapse/rest/admin/users.py
@@ -173,12 +173,11 @@ class UserRestServletV2(RestServlet):
         if not self.hs.is_mine(target_user):
             raise SynapseError(HTTPStatus.BAD_REQUEST, "Can only look up local users")
 
-        ret = await self.admin_handler.get_user(target_user)
-
-        if not ret:
+        user_info_dict = await self.admin_handler.get_user(target_user)
+        if not user_info_dict:
             raise NotFoundError("User not found")
 
-        return HTTPStatus.OK, ret
+        return HTTPStatus.OK, user_info_dict
 
     async def on_PUT(
         self, request: SynapseRequest, user_id: str
@@ -399,10 +398,10 @@ class UserRestServletV2(RestServlet):
                     target_user, requester, body["avatar_url"], True
                 )
 
-            user = await self.admin_handler.get_user(target_user)
-            assert user is not None
+            user_info_dict = await self.admin_handler.get_user(target_user)
+            assert user_info_dict is not None
 
-            return 201, user
+            return HTTPStatus.CREATED, user_info_dict
 
 
 class UserRegisterServlet(RestServlet):
diff --git a/synapse/rest/client/events.py b/synapse/rest/client/events.py
index 13b72a04..672c8210 100644
--- a/synapse/rest/client/events.py
+++ b/synapse/rest/client/events.py
@@ -91,7 +91,7 @@ class EventRestServlet(RestServlet):
 
         time_now = self.clock.time_msec()
         if event:
-            result = await self._event_serializer.serialize_event(event, time_now)
+            result = self._event_serializer.serialize_event(event, time_now)
             return 200, result
         else:
             return 404, "Event not found."
diff --git a/synapse/rest/client/notifications.py b/synapse/rest/client/notifications.py
index acd0c9e1..8e427a96 100644
--- a/synapse/rest/client/notifications.py
+++ b/synapse/rest/client/notifications.py
@@ -72,7 +72,7 @@ class NotificationsServlet(RestServlet):
                 "actions": pa.actions,
                 "ts": pa.received_ts,
                 "event": (
-                    await self._event_serializer.serialize_event(
+                    self._event_serializer.serialize_event(
                         notif_events[pa.event_id],
                         self.clock.time_msec(),
                         event_format=format_event_for_client_v2_without_room_id,
diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index 5815650e..8cf5ebaa 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -19,28 +19,20 @@ any time to reflect changes in the MSC.
 """
 
 import logging
-from typing import TYPE_CHECKING, Awaitable, Optional, Tuple
+from typing import TYPE_CHECKING, Optional, Tuple
 
-from synapse.api.constants import EventTypes, RelationTypes
-from synapse.api.errors import ShadowBanError, SynapseError
+from synapse.api.constants import RelationTypes
+from synapse.api.errors import SynapseError
 from synapse.http.server import HttpServer
-from synapse.http.servlet import (
-    RestServlet,
-    parse_integer,
-    parse_json_object_from_request,
-    parse_string,
-)
+from synapse.http.servlet import RestServlet, parse_integer, parse_string
 from synapse.http.site import SynapseRequest
-from synapse.rest.client.transactions import HttpTransactionCache
+from synapse.rest.client._base import client_patterns
 from synapse.storage.relations import (
     AggregationPaginationToken,
     PaginationChunk,
     RelationPaginationToken,
 )
 from synapse.types import JsonDict
-from synapse.util.stringutils import random_string
-
-from ._base import client_patterns
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -48,112 +40,6 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-class RelationSendServlet(RestServlet):
-    """Helper API for sending events that have relation data.
-
-    Example API shape to send a 👍 reaction to a room:
-
-        POST /rooms/!foo/send_relation/$bar/m.annotation/m.reaction?key=%F0%9F%91%8D
-        {}
-
-        {
-            "event_id": "$foobar"
-        }
-    """
-
-    PATTERN = (
-        "/rooms/(?P<room_id>[^/]*)/send_relation"
-        "/(?P<parent_id>[^/]*)/(?P<relation_type>[^/]*)/(?P<event_type>[^/]*)"
-    )
-
-    def __init__(self, hs: "HomeServer"):
-        super().__init__()
-        self.auth = hs.get_auth()
-        self.event_creation_handler = hs.get_event_creation_handler()
-        self.txns = HttpTransactionCache(hs)
-
-    def register(self, http_server: HttpServer) -> None:
-        http_server.register_paths(
-            "POST",
-            client_patterns(self.PATTERN + "$", releases=()),
-            self.on_PUT_or_POST,
-            self.__class__.__name__,
-        )
-        http_server.register_paths(
-            "PUT",
-            client_patterns(self.PATTERN + "/(?P<txn_id>[^/]*)$", releases=()),
-            self.on_PUT,
-            self.__class__.__name__,
-        )
-
-    def on_PUT(
-        self,
-        request: SynapseRequest,
-        room_id: str,
-        parent_id: str,
-        relation_type: str,
-        event_type: str,
-        txn_id: Optional[str] = None,
-    ) -> Awaitable[Tuple[int, JsonDict]]:
-        return self.txns.fetch_or_execute_request(
-            request,
-            self.on_PUT_or_POST,
-            request,
-            room_id,
-            parent_id,
-            relation_type,
-            event_type,
-            txn_id,
-        )
-
-    async def on_PUT_or_POST(
-        self,
-        request: SynapseRequest,
-        room_id: str,
-        parent_id: str,
-        relation_type: str,
-        event_type: str,
-        txn_id: Optional[str] = None,
-    ) -> Tuple[int, JsonDict]:
-        requester = await self.auth.get_user_by_req(request, allow_guest=True)
-
-        if event_type == EventTypes.Member:
-            # Add relations to a membership is meaningless, so we just deny it
-            # at the CS API rather than trying to handle it correctly.
-            raise SynapseError(400, "Cannot send member events with relations")
-
-        content = parse_json_object_from_request(request)
-
-        aggregation_key = parse_string(request, "key", encoding="utf-8")
-
-        content["m.relates_to"] = {
-            "event_id": parent_id,
-            "rel_type": relation_type,
-        }
-        if aggregation_key is not None:
-            content["m.relates_to"]["key"] = aggregation_key
-
-        event_dict = {
-            "type": event_type,
-            "content": content,
-            "room_id": room_id,
-            "sender": requester.user.to_string(),
-        }
-
-        try:
-            (
-                event,
-                _,
-            ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                requester, event_dict=event_dict, txn_id=txn_id
-            )
-            event_id = event.event_id
-        except ShadowBanError:
-            event_id = "$" + random_string(43)
-
-        return 200, {"event_id": event_id}
-
-
 class RelationPaginationServlet(RestServlet):
     """API to paginate relations on an event by topological ordering, optionally
     filtered by relation type and event type.
@@ -227,13 +113,16 @@ class RelationPaginationServlet(RestServlet):
         now = self.clock.time_msec()
         # Do not bundle aggregations when retrieving the original event because
         # we want the content before relations are applied to it.
-        original_event = await self._event_serializer.serialize_event(
-            event, now, bundle_aggregations=False
+        original_event = self._event_serializer.serialize_event(
+            event, now, bundle_aggregations=None
         )
         # The relations returned for the requested event do include their
         # bundled aggregations.
-        serialized_events = await self._event_serializer.serialize_events(
-            events, now, bundle_aggregations=True
+        aggregations = await self.store.get_bundled_aggregations(
+            events, requester.user.to_string()
+        )
+        serialized_events = self._event_serializer.serialize_events(
+            events, now, bundle_aggregations=aggregations
         )
 
         return_value = pagination_chunk.to_dict()
@@ -422,7 +311,7 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
         )
 
         now = self.clock.time_msec()
-        serialized_events = await self._event_serializer.serialize_events(events, now)
+        serialized_events = self._event_serializer.serialize_events(events, now)
 
         return_value = result.to_dict()
         return_value["chunk"] = serialized_events
@@ -431,7 +320,6 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
 
 
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
-    RelationSendServlet(hs).register(http_server)
     RelationPaginationServlet(hs).register(http_server)
     RelationAggregationPaginationServlet(hs).register(http_server)
     RelationAggregationGroupPaginationServlet(hs).register(http_server)
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index 40330749..90bb9142 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -642,6 +642,7 @@ class RoomEventServlet(RestServlet):
     def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.clock = hs.get_clock()
+        self._store = hs.get_datastore()
         self.event_handler = hs.get_event_handler()
         self._event_serializer = hs.get_event_client_serializer()
         self.auth = hs.get_auth()
@@ -660,10 +661,15 @@ class RoomEventServlet(RestServlet):
             # https://matrix.org/docs/spec/client_server/r0.5.0#get-matrix-client-r0-rooms-roomid-event-eventid
             raise SynapseError(404, "Event not found.", errcode=Codes.NOT_FOUND)
 
-        time_now = self.clock.time_msec()
         if event:
-            event_dict = await self._event_serializer.serialize_event(
-                event, time_now, bundle_aggregations=True
+            # Ensure there are bundled aggregations available.
+            aggregations = await self._store.get_bundled_aggregations(
+                [event], requester.user.to_string()
+            )
+
+            time_now = self.clock.time_msec()
+            event_dict = self._event_serializer.serialize_event(
+                event, time_now, bundle_aggregations=aggregations
             )
             return 200, event_dict
 
@@ -708,16 +714,17 @@ class RoomEventContextServlet(RestServlet):
             raise SynapseError(404, "Event not found.", errcode=Codes.NOT_FOUND)
 
         time_now = self.clock.time_msec()
-        results["events_before"] = await self._event_serializer.serialize_events(
-            results["events_before"], time_now, bundle_aggregations=True
+        aggregations = results.pop("aggregations", None)
+        results["events_before"] = self._event_serializer.serialize_events(
+            results["events_before"], time_now, bundle_aggregations=aggregations
         )
-        results["event"] = await self._event_serializer.serialize_event(
-            results["event"], time_now, bundle_aggregations=True
+        results["event"] = self._event_serializer.serialize_event(
+            results["event"], time_now, bundle_aggregations=aggregations
         )
-        results["events_after"] = await self._event_serializer.serialize_events(
-            results["events_after"], time_now, bundle_aggregations=True
+        results["events_after"] = self._event_serializer.serialize_events(
+            results["events_after"], time_now, bundle_aggregations=aggregations
         )
-        results["state"] = await self._event_serializer.serialize_events(
+        results["state"] = self._event_serializer.serialize_events(
             results["state"], time_now
         )
 
diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py
index e99a943d..d20ae142 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -17,7 +17,6 @@ from collections import defaultdict
 from typing import (
     TYPE_CHECKING,
     Any,
-    Awaitable,
     Callable,
     Dict,
     Iterable,
@@ -395,7 +394,7 @@ class SyncRestServlet(RestServlet):
         """
         invited = {}
         for room in rooms:
-            invite = await self._event_serializer.serialize_event(
+            invite = self._event_serializer.serialize_event(
                 room.invite,
                 time_now,
                 token_id=token_id,
@@ -432,7 +431,7 @@ class SyncRestServlet(RestServlet):
         """
         knocked = {}
         for room in rooms:
-            knock = await self._event_serializer.serialize_event(
+            knock = self._event_serializer.serialize_event(
                 room.knock,
                 time_now,
                 token_id=token_id,
@@ -525,21 +524,14 @@ class SyncRestServlet(RestServlet):
             The room, encoded in our response format
         """
 
-        def serialize(events: Iterable[EventBase]) -> Awaitable[List[JsonDict]]:
+        def serialize(
+            events: Iterable[EventBase],
+            aggregations: Optional[Dict[str, Dict[str, Any]]] = None,
+        ) -> List[JsonDict]:
             return self._event_serializer.serialize_events(
                 events,
                 time_now=time_now,
-                # Don't bother to bundle aggregations if the timeline is unlimited,
-                # as clients will have all the necessary information.
-                # bundle_aggregations=room.timeline.limited,
-                #
-                # richvdh 2021-12-15: disable this temporarily as it has too high an
-                # overhead for initialsyncs. We need to figure out a way that the
-                # bundling can be done *before* the events are stored in the
-                # SyncResponseCache so that this part can be synchronous.
-                #
-                # Ensure to re-enable the test at tests/rest/client/test_relations.py::RelationsTestCase.test_bundled_aggregations.
-                bundle_aggregations=False,
+                bundle_aggregations=aggregations,
                 token_id=token_id,
                 event_format=event_formatter,
                 only_event_fields=only_fields,
@@ -561,8 +553,10 @@ class SyncRestServlet(RestServlet):
                     event.room_id,
                 )
 
-        serialized_state = await serialize(state_events)
-        serialized_timeline = await serialize(timeline_events)
+        serialized_state = serialize(state_events)
+        serialized_timeline = serialize(
+            timeline_events, room.timeline.bundled_aggregations
+        )
 
         account_data = room.account_data
 
diff --git a/synapse/rest/media/v1/media_storage.py b/synapse/rest/media/v1/media_storage.py
index fca239d8..9f6c251c 100644
--- a/synapse/rest/media/v1/media_storage.py
+++ b/synapse/rest/media/v1/media_storage.py
@@ -343,7 +343,7 @@ class SpamMediaException(NotFoundError):
     """
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class ReadableFileWrapper:
     """Wrapper that allows reading a file in chunks, yielding to the reactor,
     and writing to a callback.
@@ -354,8 +354,8 @@ class ReadableFileWrapper:
 
     CHUNK_SIZE = 2 ** 14
 
-    clock = attr.ib(type=Clock)
-    path = attr.ib(type=str)
+    clock: Clock
+    path: str
 
     async def write_chunks_to(self, callback: Callable[[bytes], None]) -> None:
         """Reads the file in chunks and calls the callback with each chunk."""
diff --git a/synapse/rest/media/v1/oembed.py b/synapse/rest/media/v1/oembed.py
index cce1527e..2177b46c 100644
--- a/synapse/rest/media/v1/oembed.py
+++ b/synapse/rest/media/v1/oembed.py
@@ -33,6 +33,8 @@ logger = logging.getLogger(__name__)
 class OEmbedResult:
     # The Open Graph result (converted from the oEmbed result).
     open_graph_result: JsonDict
+    # The author_name of the oEmbed result
+    author_name: Optional[str]
     # Number of milliseconds to cache the content, according to the oEmbed response.
     #
     # This will be None if no cache-age is provided in the oEmbed response (or
@@ -154,11 +156,12 @@ class OEmbedProvider:
                 "og:url": url,
             }
 
-            # Use either title or author's name as the title.
-            title = oembed.get("title") or oembed.get("author_name")
+            title = oembed.get("title")
             if title:
                 open_graph_response["og:title"] = title
 
+            author_name = oembed.get("author_name")
+
             # Use the provider name and as the site.
             provider_name = oembed.get("provider_name")
             if provider_name:
@@ -193,9 +196,10 @@ class OEmbedProvider:
             # Trap any exception and let the code follow as usual.
             logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
             open_graph_response = {}
+            author_name = None
             cache_age = None
 
-        return OEmbedResult(open_graph_response, cache_age)
+        return OEmbedResult(open_graph_response, author_name, cache_age)
 
 
 def _fetch_urls(tree: "etree.Element", tag_name: str) -> List[str]:
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index a3829d94..e8881bc8 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -262,6 +262,7 @@ class PreviewUrlResource(DirectServeJsonResource):
 
         # The number of milliseconds that the response should be considered valid.
         expiration_ms = media_info.expires
+        author_name: Optional[str] = None
 
         if _is_media(media_info.media_type):
             file_id = media_info.filesystem_id
@@ -294,17 +295,25 @@ class PreviewUrlResource(DirectServeJsonResource):
                 # Check if this HTML document points to oEmbed information and
                 # defer to that.
                 oembed_url = self._oembed.autodiscover_from_html(tree)
-                og = {}
+                og_from_oembed: JsonDict = {}
                 if oembed_url:
                     oembed_info = await self._download_url(oembed_url, user)
-                    og, expiration_ms = await self._handle_oembed_response(
+                    (
+                        og_from_oembed,
+                        author_name,
+                        expiration_ms,
+                    ) = await self._handle_oembed_response(
                         url, oembed_info, expiration_ms
                     )
 
-                # If there was no oEmbed URL (or oEmbed parsing failed), attempt
-                # to generate the Open Graph information from the HTML.
-                if not oembed_url or not og:
-                    og = parse_html_to_open_graph(tree, media_info.uri)
+                # Parse Open Graph information from the HTML in case the oEmbed
+                # response failed or is incomplete.
+                og_from_html = parse_html_to_open_graph(tree, media_info.uri)
+
+                # Compile the Open Graph response by using the scraped
+                # information from the HTML and overlaying any information
+                # from the oEmbed response.
+                og = {**og_from_html, **og_from_oembed}
 
                 await self._precache_image_url(user, media_info, og)
             else:
@@ -312,7 +321,7 @@ class PreviewUrlResource(DirectServeJsonResource):
 
         elif oembed_url:
             # Handle the oEmbed information.
-            og, expiration_ms = await self._handle_oembed_response(
+            og, author_name, expiration_ms = await self._handle_oembed_response(
                 url, media_info, expiration_ms
             )
             await self._precache_image_url(user, media_info, og)
@@ -321,6 +330,11 @@ class PreviewUrlResource(DirectServeJsonResource):
             logger.warning("Failed to find any OG data in %s", url)
             og = {}
 
+        # If we don't have a title but we have author_name, copy it as
+        # title
+        if not og.get("og:title") and author_name:
+            og["og:title"] = author_name
+
         # filter out any stupidly long values
         keys_to_remove = []
         for k, v in og.items():
@@ -484,7 +498,7 @@ class PreviewUrlResource(DirectServeJsonResource):
 
     async def _handle_oembed_response(
         self, url: str, media_info: MediaInfo, expiration_ms: int
-    ) -> Tuple[JsonDict, int]:
+    ) -> Tuple[JsonDict, Optional[str], int]:
         """
         Parse the downloaded oEmbed info.
 
@@ -497,11 +511,12 @@ class PreviewUrlResource(DirectServeJsonResource):
         Returns:
             A tuple of:
                 The Open Graph dictionary, if the oEmbed info can be parsed.
+                The author name if it could be retrieved from oEmbed.
                 The (possibly updated) length of time, in milliseconds, the media is valid for.
         """
         # If JSON was not returned, there's nothing to do.
         if not _is_json(media_info.media_type):
-            return {}, expiration_ms
+            return {}, None, expiration_ms
 
         with open(media_info.filename, "rb") as file:
             body = file.read()
@@ -513,7 +528,7 @@ class PreviewUrlResource(DirectServeJsonResource):
         if open_graph_result and oembed_response.cache_age is not None:
             expiration_ms = oembed_response.cache_age
 
-        return open_graph_result, expiration_ms
+        return open_graph_result, oembed_response.author_name, expiration_ms
 
     def _start_expire_url_cache_data(self) -> Deferred:
         return run_as_background_process(
diff --git a/synapse/server.py b/synapse/server.py
index 185e40e4..3032f0b7 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -759,7 +759,7 @@ class HomeServer(metaclass=abc.ABCMeta):
 
     @cache_in_self
     def get_event_client_serializer(self) -> EventClientSerializer:
-        return EventClientSerializer(self)
+        return EventClientSerializer()
 
     @cache_in_self
     def get_password_policy_handler(self) -> PasswordPolicyHandler:
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index 69ac8c34..67e8bc6e 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -45,7 +45,6 @@ from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, StateResolutionVersio
 from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.logging.context import ContextResourceUsage
-from synapse.logging.utils import log_function
 from synapse.state import v1, v2
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.storage.roommember import ProfileInfo
@@ -450,19 +449,19 @@ class StateHandler:
         return {key: state_map[ev_id] for key, ev_id in new_state.items()}
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _StateResMetrics:
     """Keeps track of some usage metrics about state res."""
 
     # System and User CPU time, in seconds
-    cpu_time = attr.ib(type=float, default=0.0)
+    cpu_time: float = 0.0
 
     # time spent on database transactions (excluding scheduling time). This roughly
     # corresponds to the amount of work done on the db server, excluding event fetches.
-    db_time = attr.ib(type=float, default=0.0)
+    db_time: float = 0.0
 
     # number of events fetched from the db.
-    db_events = attr.ib(type=int, default=0)
+    db_events: int = 0
 
 
 _biggest_room_by_cpu_counter = Counter(
@@ -512,7 +511,6 @@ class StateResolutionHandler:
 
         self.clock.looping_call(self._report_metrics, 120 * 1000)
 
-    @log_function
     async def resolve_state_groups(
         self,
         room_id: str,
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 2cacc7dd..57cc1d76 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -143,7 +143,7 @@ def make_conn(
     return db_conn
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class LoggingDatabaseConnection:
     """A wrapper around a database connection that returns `LoggingTransaction`
     as its cursor class.
@@ -151,9 +151,9 @@ class LoggingDatabaseConnection:
     This is mainly used on startup to ensure that queries get logged correctly
     """
 
-    conn = attr.ib(type=Connection)
-    engine = attr.ib(type=BaseDatabaseEngine)
-    default_txn_name = attr.ib(type=str)
+    conn: Connection
+    engine: BaseDatabaseEngine
+    default_txn_name: str
 
     def cursor(
         self, *, txn_name=None, after_callbacks=None, exception_callbacks=None
@@ -934,56 +934,6 @@ class DatabasePool:
         txn.execute(sql, vals)
 
     async def simple_insert_many(
-        self, table: str, values: List[Dict[str, Any]], desc: str
-    ) -> None:
-        """Executes an INSERT query on the named table.
-
-        The input is given as a list of dicts, with one dict per row.
-        Generally simple_insert_many_values should be preferred for new code.
-
-        Args:
-            table: string giving the table name
-            values: dict of new column names and values for them
-            desc: description of the transaction, for logging and metrics
-        """
-        await self.runInteraction(desc, self.simple_insert_many_txn, table, values)
-
-    @staticmethod
-    def simple_insert_many_txn(
-        txn: LoggingTransaction, table: str, values: List[Dict[str, Any]]
-    ) -> None:
-        """Executes an INSERT query on the named table.
-
-        The input is given as a list of dicts, with one dict per row.
-        Generally simple_insert_many_values_txn should be preferred for new code.
-
-        Args:
-            txn: The transaction to use.
-            table: string giving the table name
-            values: dict of new column names and values for them
-        """
-        if not values:
-            return
-
-        # This is a *slight* abomination to get a list of tuples of key names
-        # and a list of tuples of value names.
-        #
-        # i.e. [{"a": 1, "b": 2}, {"c": 3, "d": 4}]
-        #         => [("a", "b",), ("c", "d",)] and [(1, 2,), (3, 4,)]
-        #
-        # The sort is to ensure that we don't rely on dictionary iteration
-        # order.
-        keys, vals = zip(
-            *(zip(*(sorted(i.items(), key=lambda kv: kv[0]))) for i in values if i)
-        )
-
-        for k in keys:
-            if k != keys[0]:
-                raise RuntimeError("All items must have the same keys")
-
-        return DatabasePool.simple_insert_many_values_txn(txn, table, keys[0], vals)
-
-    async def simple_insert_many_values(
         self,
         table: str,
         keys: Collection[str],
@@ -1002,11 +952,11 @@ class DatabasePool:
             desc: description of the transaction, for logging and metrics
         """
         await self.runInteraction(
-            desc, self.simple_insert_many_values_txn, table, keys, values
+            desc, self.simple_insert_many_txn, table, keys, values
         )
 
     @staticmethod
-    def simple_insert_many_values_txn(
+    def simple_insert_many_txn(
         txn: LoggingTransaction,
         table: str,
         keys: Collection[str],
diff --git a/synapse/storage/databases/main/account_data.py b/synapse/storage/databases/main/account_data.py
index 32a553fd..ef475e18 100644
--- a/synapse/storage/databases/main/account_data.py
+++ b/synapse/storage/databases/main/account_data.py
@@ -450,7 +450,7 @@ class AccountDataWorkerStore(CacheInvalidationWorkerStore):
     async def add_account_data_for_user(
         self, user_id: str, account_data_type: str, content: JsonDict
     ) -> int:
-        """Add some account_data to a room for a user.
+        """Add some global account_data for a user.
 
         Args:
             user_id: The user to add a tag for.
@@ -536,9 +536,9 @@ class AccountDataWorkerStore(CacheInvalidationWorkerStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="ignored_users",
+            keys=("ignorer_user_id", "ignored_user_id"),
             values=[
-                {"ignorer_user_id": user_id, "ignored_user_id": u}
-                for u in currently_ignored_users - previously_ignored_users
+                (user_id, u) for u in currently_ignored_users - previously_ignored_users
             ],
         )
 
diff --git a/synapse/storage/databases/main/deviceinbox.py b/synapse/storage/databases/main/deviceinbox.py
index 3682cb6a..4eca9718 100644
--- a/synapse/storage/databases/main/deviceinbox.py
+++ b/synapse/storage/databases/main/deviceinbox.py
@@ -432,14 +432,21 @@ class DeviceInboxWorkerStore(SQLBaseStore):
             self.db_pool.simple_insert_many_txn(
                 txn,
                 table="device_federation_outbox",
+                keys=(
+                    "destination",
+                    "stream_id",
+                    "queued_ts",
+                    "messages_json",
+                    "instance_name",
+                ),
                 values=[
-                    {
-                        "destination": destination,
-                        "stream_id": stream_id,
-                        "queued_ts": now_ms,
-                        "messages_json": json_encoder.encode(edu),
-                        "instance_name": self._instance_name,
-                    }
+                    (
+                        destination,
+                        stream_id,
+                        now_ms,
+                        json_encoder.encode(edu),
+                        self._instance_name,
+                    )
                     for destination, edu in remote_messages_by_destination.items()
                 ],
             )
@@ -571,14 +578,9 @@ class DeviceInboxWorkerStore(SQLBaseStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="device_inbox",
+            keys=("user_id", "device_id", "stream_id", "message_json", "instance_name"),
             values=[
-                {
-                    "user_id": user_id,
-                    "device_id": device_id,
-                    "stream_id": stream_id,
-                    "message_json": message_json,
-                    "instance_name": self._instance_name,
-                }
+                (user_id, device_id, stream_id, message_json, self._instance_name)
                 for user_id, messages_by_device in local_by_user_then_device.items()
                 for device_id, message_json in messages_by_device.items()
             ],
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index bc7e8760..b2a5cd9a 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -53,6 +53,7 @@ if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
+issue_8631_logger = logging.getLogger("synapse.8631_debug")
 
 DROP_DEVICE_LIST_STREAMS_NON_UNIQUE_INDEXES = (
     "drop_device_list_streams_non_unique_indexes"
@@ -229,6 +230,12 @@ class DeviceWorkerStore(SQLBaseStore):
         if not updates:
             return now_stream_id, []
 
+        if issue_8631_logger.isEnabledFor(logging.DEBUG):
+            data = {(user, device): stream_id for user, device, stream_id, _ in updates}
+            issue_8631_logger.debug(
+                "device updates need to be sent to %s: %s", destination, data
+            )
+
         # get the cross-signing keys of the users in the list, so that we can
         # determine which of the device changes were cross-signing keys
         users = {r[0] for r in updates}
@@ -365,6 +372,17 @@ class DeviceWorkerStore(SQLBaseStore):
             #        and remove the length budgeting above.
             results.append(("org.matrix.signing_key_update", result))
 
+        if issue_8631_logger.isEnabledFor(logging.DEBUG):
+            for (user_id, edu) in results:
+                issue_8631_logger.debug(
+                    "device update to %s for %s from %s to %s: %s",
+                    destination,
+                    user_id,
+                    from_stream_id,
+                    last_processed_stream_id,
+                    edu,
+                )
+
         return last_processed_stream_id, results
 
     def _get_device_updates_by_remote_txn(
@@ -781,7 +799,7 @@ class DeviceWorkerStore(SQLBaseStore):
     @cached(max_entries=10000)
     async def get_device_list_last_stream_id_for_remote(
         self, user_id: str
-    ) -> Optional[Any]:
+    ) -> Optional[str]:
         """Get the last stream_id we got for a user. May be None if we haven't
         got any information for them.
         """
@@ -797,7 +815,9 @@ class DeviceWorkerStore(SQLBaseStore):
         cached_method_name="get_device_list_last_stream_id_for_remote",
         list_name="user_ids",
     )
-    async def get_device_list_last_stream_id_for_remotes(self, user_ids: Iterable[str]):
+    async def get_device_list_last_stream_id_for_remotes(
+        self, user_ids: Iterable[str]
+    ) -> Dict[str, Optional[str]]:
         rows = await self.db_pool.simple_select_many_batch(
             table="device_lists_remote_extremeties",
             column="user_id",
@@ -1384,6 +1404,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         content: JsonDict,
         stream_id: str,
     ) -> None:
+        """Delete, update or insert a cache entry for this (user, device) pair."""
         if content.get("deleted"):
             self.db_pool.simple_delete_txn(
                 txn,
@@ -1443,6 +1464,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
     def _update_remote_device_list_cache_txn(
         self, txn: LoggingTransaction, user_id: str, devices: List[dict], stream_id: int
     ) -> None:
+        """Replace the list of cached devices for this user with the given list."""
         self.db_pool.simple_delete_txn(
             txn, table="device_lists_remote_cache", keyvalues={"user_id": user_id}
         )
@@ -1450,12 +1472,9 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="device_lists_remote_cache",
+            keys=("user_id", "device_id", "content"),
             values=[
-                {
-                    "user_id": user_id,
-                    "device_id": content["device_id"],
-                    "content": json_encoder.encode(content),
-                }
+                (user_id, content["device_id"], json_encoder.encode(content))
                 for content in devices
             ],
         )
@@ -1543,8 +1562,9 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="device_lists_stream",
+            keys=("stream_id", "user_id", "device_id"),
             values=[
-                {"stream_id": stream_id, "user_id": user_id, "device_id": device_id}
+                (stream_id, user_id, device_id)
                 for stream_id, device_id in zip(stream_ids, device_ids)
             ],
         )
@@ -1571,18 +1591,27 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="device_lists_outbound_pokes",
+            keys=(
+                "destination",
+                "stream_id",
+                "user_id",
+                "device_id",
+                "sent",
+                "ts",
+                "opentracing_context",
+            ),
             values=[
-                {
-                    "destination": destination,
-                    "stream_id": next(next_stream_id),
-                    "user_id": user_id,
-                    "device_id": device_id,
-                    "sent": False,
-                    "ts": now,
-                    "opentracing_context": json_encoder.encode(context)
+                (
+                    destination,
+                    next(next_stream_id),
+                    user_id,
+                    device_id,
+                    False,
+                    now,
+                    json_encoder.encode(context)
                     if whitelisted_homeserver(destination)
                     else "{}",
-                }
+                )
                 for destination in hosts
                 for device_id in device_ids
             ],
diff --git a/synapse/storage/databases/main/directory.py b/synapse/storage/databases/main/directory.py
index f76c6121..5903fdaf 100644
--- a/synapse/storage/databases/main/directory.py
+++ b/synapse/storage/databases/main/directory.py
@@ -112,10 +112,8 @@ class DirectoryWorkerStore(CacheInvalidationWorkerStore):
             self.db_pool.simple_insert_many_txn(
                 txn,
                 table="room_alias_servers",
-                values=[
-                    {"room_alias": room_alias.to_string(), "server": server}
-                    for server in servers
-                ],
+                keys=("room_alias", "server"),
+                values=[(room_alias.to_string(), server) for server in servers],
             )
 
             self._invalidate_cache_and_stream(
diff --git a/synapse/storage/databases/main/e2e_room_keys.py b/synapse/storage/databases/main/e2e_room_keys.py
index 0cb48b9d..b789a588 100644
--- a/synapse/storage/databases/main/e2e_room_keys.py
+++ b/synapse/storage/databases/main/e2e_room_keys.py
@@ -110,16 +110,16 @@ class EndToEndRoomKeyStore(SQLBaseStore):
         values = []
         for (room_id, session_id, room_key) in room_keys:
             values.append(
-                {
-                    "user_id": user_id,
-                    "version": version_int,
-                    "room_id": room_id,
-                    "session_id": session_id,
-                    "first_message_index": room_key["first_message_index"],
-                    "forwarded_count": room_key["forwarded_count"],
-                    "is_verified": room_key["is_verified"],
-                    "session_data": json_encoder.encode(room_key["session_data"]),
-                }
+                (
+                    user_id,
+                    version_int,
+                    room_id,
+                    session_id,
+                    room_key["first_message_index"],
+                    room_key["forwarded_count"],
+                    room_key["is_verified"],
+                    json_encoder.encode(room_key["session_data"]),
+                )
             )
             log_kv(
                 {
@@ -131,7 +131,19 @@ class EndToEndRoomKeyStore(SQLBaseStore):
             )
 
         await self.db_pool.simple_insert_many(
-            table="e2e_room_keys", values=values, desc="add_e2e_room_keys"
+            table="e2e_room_keys",
+            keys=(
+                "user_id",
+                "version",
+                "room_id",
+                "session_id",
+                "first_message_index",
+                "forwarded_count",
+                "is_verified",
+                "session_data",
+            ),
+            values=values,
+            desc="add_e2e_room_keys",
         )
 
     @trace
diff --git a/synapse/storage/databases/main/end_to_end_keys.py b/synapse/storage/databases/main/end_to_end_keys.py
index 57b5ffba..1f8447b5 100644
--- a/synapse/storage/databases/main/end_to_end_keys.py
+++ b/synapse/storage/databases/main/end_to_end_keys.py
@@ -50,16 +50,16 @@ if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class DeviceKeyLookupResult:
     """The type returned by get_e2e_device_keys_and_signatures"""
 
-    display_name = attr.ib(type=Optional[str])
+    display_name: Optional[str]
 
     # the key data from e2e_device_keys_json. Typically includes fields like
     # "algorithm", "keys" (including the curve25519 identity key and the ed25519 signing
     # key) and "signatures" (a map from (user id) to (key id/device_id) to signature.)
-    keys = attr.ib(type=Optional[JsonDict])
+    keys: Optional[JsonDict]
 
 
 class EndToEndKeyBackgroundStore(SQLBaseStore):
@@ -387,15 +387,16 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore, CacheInvalidationWorker
             self.db_pool.simple_insert_many_txn(
                 txn,
                 table="e2e_one_time_keys_json",
+                keys=(
+                    "user_id",
+                    "device_id",
+                    "algorithm",
+                    "key_id",
+                    "ts_added_ms",
+                    "key_json",
+                ),
                 values=[
-                    {
-                        "user_id": user_id,
-                        "device_id": device_id,
-                        "algorithm": algorithm,
-                        "key_id": key_id,
-                        "ts_added_ms": time_now,
-                        "key_json": json_bytes,
-                    }
+                    (user_id, device_id, algorithm, key_id, time_now, json_bytes)
                     for algorithm, key_id, json_bytes in new_keys
                 ],
             )
@@ -1186,15 +1187,22 @@ class EndToEndKeyStore(EndToEndKeyWorkerStore, SQLBaseStore):
         """
         await self.db_pool.simple_insert_many(
             "e2e_cross_signing_signatures",
-            [
-                {
-                    "user_id": user_id,
-                    "key_id": item.signing_key_id,
-                    "target_user_id": item.target_user_id,
-                    "target_device_id": item.target_device_id,
-                    "signature": item.signature,
-                }
+            keys=(
+                "user_id",
+                "key_id",
+                "target_user_id",
+                "target_device_id",
+                "signature",
+            ),
+            values=[
+                (
+                    user_id,
+                    item.signing_key_id,
+                    item.target_user_id,
+                    item.target_device_id,
+                    item.signature,
+                )
                 for item in signatures
             ],
-            "add_e2e_signing_key",
+            desc="add_e2e_signing_key",
         )
diff --git a/synapse/storage/databases/main/event_push_actions.py b/synapse/storage/databases/main/event_push_actions.py
index a98e6b25..b7c4c622 100644
--- a/synapse/storage/databases/main/event_push_actions.py
+++ b/synapse/storage/databases/main/event_push_actions.py
@@ -875,14 +875,21 @@ class EventPushActionsWorkerStore(SQLBaseStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_push_summary",
+            keys=(
+                "user_id",
+                "room_id",
+                "notif_count",
+                "unread_count",
+                "stream_ordering",
+            ),
             values=[
-                {
-                    "user_id": user_id,
-                    "room_id": room_id,
-                    "notif_count": summary.notif_count,
-                    "unread_count": summary.unread_count,
-                    "stream_ordering": summary.stream_ordering,
-                }
+                (
+                    user_id,
+                    room_id,
+                    summary.notif_count,
+                    summary.unread_count,
+                    summary.stream_ordering,
+                )
                 for ((user_id, room_id), summary) in summaries.items()
                 if summary.old_user_id is None
             ],
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index dd255aef..1ae1ebe1 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -39,7 +39,6 @@ from synapse.api.room_versions import RoomVersions
 from synapse.crypto.event_signing import compute_event_reference_hash
 from synapse.events import EventBase  # noqa: F401
 from synapse.events.snapshot import EventContext  # noqa: F401
-from synapse.logging.utils import log_function
 from synapse.storage._base import db_to_json, make_in_list_sql_clause
 from synapse.storage.database import (
     DatabasePool,
@@ -69,7 +68,7 @@ event_counter = Counter(
 )
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class DeltaState:
     """Deltas to use to update the `current_state_events` table.
 
@@ -80,9 +79,9 @@ class DeltaState:
             should e.g. be removed from `current_state_events` table.
     """
 
-    to_delete = attr.ib(type=List[Tuple[str, str]])
-    to_insert = attr.ib(type=StateMap[str])
-    no_longer_in_room = attr.ib(type=bool, default=False)
+    to_delete: List[Tuple[str, str]]
+    to_insert: StateMap[str]
+    no_longer_in_room: bool = False
 
 
 class PersistEventsStore:
@@ -328,7 +327,6 @@ class PersistEventsStore:
 
         return existing_prevs
 
-    @log_function
     def _persist_events_txn(
         self,
         txn: LoggingTransaction,
@@ -442,12 +440,9 @@ class PersistEventsStore:
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_auth",
+            keys=("event_id", "room_id", "auth_id"),
             values=[
-                {
-                    "event_id": event.event_id,
-                    "room_id": event.room_id,
-                    "auth_id": auth_id,
-                }
+                (event.event_id, event.room_id, auth_id)
                 for event in events
                 for auth_id in event.auth_event_ids()
                 if event.is_state()
@@ -675,8 +670,9 @@ class PersistEventsStore:
         db_pool.simple_insert_many_txn(
             txn,
             table="event_auth_chains",
+            keys=("event_id", "chain_id", "sequence_number"),
             values=[
-                {"event_id": event_id, "chain_id": c_id, "sequence_number": seq}
+                (event_id, c_id, seq)
                 for event_id, (c_id, seq) in new_chain_tuples.items()
             ],
         )
@@ -782,13 +778,14 @@ class PersistEventsStore:
         db_pool.simple_insert_many_txn(
             txn,
             table="event_auth_chain_links",
+            keys=(
+                "origin_chain_id",
+                "origin_sequence_number",
+                "target_chain_id",
+                "target_sequence_number",
+            ),
             values=[
-                {
-                    "origin_chain_id": source_id,
-                    "origin_sequence_number": source_seq,
-                    "target_chain_id": target_id,
-                    "target_sequence_number": target_seq,
-                }
+                (source_id, source_seq, target_id, target_seq)
                 for (
                     source_id,
                     source_seq,
@@ -943,20 +940,28 @@ class PersistEventsStore:
             txn_id = getattr(event.internal_metadata, "txn_id", None)
             if token_id and txn_id:
                 to_insert.append(
-                    {
-                        "event_id": event.event_id,
-                        "room_id": event.room_id,
-                        "user_id": event.sender,
-                        "token_id": token_id,
-                        "txn_id": txn_id,
-                        "inserted_ts": self._clock.time_msec(),
-                    }
+                    (
+                        event.event_id,
+                        event.room_id,
+                        event.sender,
+                        token_id,
+                        txn_id,
+                        self._clock.time_msec(),
+                    )
                 )
 
         if to_insert:
             self.db_pool.simple_insert_many_txn(
                 txn,
                 table="event_txn_id",
+                keys=(
+                    "event_id",
+                    "room_id",
+                    "user_id",
+                    "token_id",
+                    "txn_id",
+                    "inserted_ts",
+                ),
                 values=to_insert,
             )
 
@@ -1161,8 +1166,9 @@ class PersistEventsStore:
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_forward_extremities",
+            keys=("event_id", "room_id"),
             values=[
-                {"event_id": ev_id, "room_id": room_id}
+                (ev_id, room_id)
                 for room_id, new_extrem in new_forward_extremities.items()
                 for ev_id in new_extrem
             ],
@@ -1174,12 +1180,9 @@ class PersistEventsStore:
         self.db_pool.simple_insert_many_txn(
             txn,
             table="stream_ordering_to_exterm",
+            keys=("room_id", "event_id", "stream_ordering"),
             values=[
-                {
-                    "room_id": room_id,
-                    "event_id": event_id,
-                    "stream_ordering": max_stream_order,
-                }
+                (room_id, event_id, max_stream_order)
                 for room_id, new_extrem in new_forward_extremities.items()
                 for event_id in new_extrem
             ],
@@ -1251,20 +1254,22 @@ class PersistEventsStore:
         for room_id, depth in depth_updates.items():
             self._update_min_depth_for_room_txn(txn, room_id, depth)
 
-    def _update_outliers_txn(self, txn, events_and_contexts):
+    def _update_outliers_txn(
+        self,
+        txn: LoggingTransaction,
+        events_and_contexts: List[Tuple[EventBase, EventContext]],
+    ) -> List[Tuple[EventBase, EventContext]]:
         """Update any outliers with new event info.
 
-        This turns outliers into ex-outliers (unless the new event was
-        rejected).
+        This turns outliers into ex-outliers (unless the new event was rejected), and
+        also removes any other events we have already seen from the list.
 
         Args:
-            txn (twisted.enterprise.adbapi.Connection): db connection
-            events_and_contexts (list[(EventBase, EventContext)]): events
-                we are persisting
+            txn: db connection
+            events_and_contexts: events we are persisting
 
         Returns:
-            list[(EventBase, EventContext)] new list, without events which
-            are already in the events table.
+            new list, without events which are already in the events table.
         """
         txn.execute(
             "SELECT event_id, outlier FROM events WHERE event_id in (%s)"
@@ -1272,7 +1277,9 @@ class PersistEventsStore:
             [event.event_id for event, _ in events_and_contexts],
         )
 
-        have_persisted = {event_id: outlier for event_id, outlier in txn}
+        have_persisted: Dict[str, bool] = {
+            event_id: outlier for event_id, outlier in txn
+        }
 
         to_remove = set()
         for event, context in events_and_contexts:
@@ -1282,15 +1289,22 @@ class PersistEventsStore:
             to_remove.add(event)
 
             if context.rejected:
-                # If the event is rejected then we don't care if the event
-                # was an outlier or not.
+                # If the incoming event is rejected then we don't care if the event
+                # was an outlier or not - what we have is at least as good.
                 continue
 
             outlier_persisted = have_persisted[event.event_id]
             if not event.internal_metadata.is_outlier() and outlier_persisted:
                 # We received a copy of an event that we had already stored as
-                # an outlier in the database. We now have some state at that
+                # an outlier in the database. We now have some state at that event
                 # so we need to update the state_groups table with that state.
+                #
+                # Note that we do not update the stream_ordering of the event in this
+                # scenario. XXX: does this cause bugs? It will mean we won't send such
+                # events down /sync. In general they will be historical events, so that
+                # doesn't matter too much, but that is not always the case.
+
+                logger.info("Updating state for ex-outlier event %s", event.event_id)
 
                 # insert into event_to_state_groups.
                 try:
@@ -1342,7 +1356,7 @@ class PersistEventsStore:
             d.pop("redacted_because", None)
             return d
 
-        self.db_pool.simple_insert_many_values_txn(
+        self.db_pool.simple_insert_many_txn(
             txn,
             table="event_json",
             keys=("event_id", "room_id", "internal_metadata", "json", "format_version"),
@@ -1358,7 +1372,7 @@ class PersistEventsStore:
             ),
         )
 
-        self.db_pool.simple_insert_many_values_txn(
+        self.db_pool.simple_insert_many_txn(
             txn,
             table="events",
             keys=(
@@ -1412,7 +1426,7 @@ class PersistEventsStore:
         )
         txn.execute(sql + clause, [False] + args)
 
-        self.db_pool.simple_insert_many_values_txn(
+        self.db_pool.simple_insert_many_txn(
             txn,
             table="state_events",
             keys=("event_id", "room_id", "type", "state_key"),
@@ -1622,14 +1636,9 @@ class PersistEventsStore:
         return self.db_pool.simple_insert_many_txn(
             txn=txn,
             table="event_labels",
+            keys=("event_id", "label", "room_id", "topological_ordering"),
             values=[
-                {
-                    "event_id": event_id,
-                    "label": label,
-                    "room_id": room_id,
-                    "topological_ordering": topological_ordering,
-                }
-                for label in labels
+                (event_id, label, room_id, topological_ordering) for label in labels
             ],
         )
 
@@ -1657,16 +1666,13 @@ class PersistEventsStore:
         vals = []
         for event in events:
             ref_alg, ref_hash_bytes = compute_event_reference_hash(event)
-            vals.append(
-                {
-                    "event_id": event.event_id,
-                    "algorithm": ref_alg,
-                    "hash": memoryview(ref_hash_bytes),
-                }
-            )
+            vals.append((event.event_id, ref_alg, memoryview(ref_hash_bytes)))
 
         self.db_pool.simple_insert_many_txn(
-            txn, table="event_reference_hashes", values=vals
+            txn,
+            table="event_reference_hashes",
+            keys=("event_id", "algorithm", "hash"),
+            values=vals,
         )
 
     def _store_room_members_txn(
@@ -1689,18 +1695,25 @@ class PersistEventsStore:
         self.db_pool.simple_insert_many_txn(
             txn,
             table="room_memberships",
+            keys=(
+                "event_id",
+                "user_id",
+                "sender",
+                "room_id",
+                "membership",
+                "display_name",
+                "avatar_url",
+            ),
             values=[
-                {
-                    "event_id": event.event_id,
-                    "user_id": event.state_key,
-                    "sender": event.user_id,
-                    "room_id": event.room_id,
-                    "membership": event.membership,
-                    "display_name": non_null_str_or_none(
-                        event.content.get("displayname")
-                    ),
-                    "avatar_url": non_null_str_or_none(event.content.get("avatar_url")),
-                }
+                (
+                    event.event_id,
+                    event.state_key,
+                    event.user_id,
+                    event.room_id,
+                    event.membership,
+                    non_null_str_or_none(event.content.get("displayname")),
+                    non_null_str_or_none(event.content.get("avatar_url")),
+                )
                 for event in events
             ],
         )
@@ -1791,6 +1804,13 @@ class PersistEventsStore:
             txn.call_after(
                 self.store.get_thread_summary.invalidate, (parent_id, event.room_id)
             )
+            # It should be safe to only invalidate the cache if the user has not
+            # previously participated in the thread, but that's difficult (and
+            # potentially error-prone) so it is always invalidated.
+            txn.call_after(
+                self.store.get_thread_participated.invalidate,
+                (parent_id, event.room_id, event.sender),
+            )
 
     def _handle_insertion_event(self, txn: LoggingTransaction, event: EventBase):
         """Handles keeping track of insertion events and edges/connections.
@@ -2163,13 +2183,9 @@ class PersistEventsStore:
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_edges",
+            keys=("event_id", "prev_event_id", "room_id", "is_state"),
             values=[
-                {
-                    "event_id": ev.event_id,
-                    "prev_event_id": e_id,
-                    "room_id": ev.room_id,
-                    "is_state": False,
-                }
+                (ev.event_id, e_id, ev.room_id, False)
                 for ev in events
                 for e_id in ev.prev_event_ids()
             ],
@@ -2226,17 +2242,17 @@ class PersistEventsStore:
         )
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _LinkMap:
     """A helper type for tracking links between chains."""
 
     # Stores the set of links as nested maps: source chain ID -> target chain ID
     # -> source sequence number -> target sequence number.
-    maps = attr.ib(type=Dict[int, Dict[int, Dict[int, int]]], factory=dict)
+    maps: Dict[int, Dict[int, Dict[int, int]]] = attr.Factory(dict)
 
     # Stores the links that have been added (with new set to true), as tuples of
     # `(source chain ID, source sequence no, target chain ID, target sequence no.)`
-    additions = attr.ib(type=Set[Tuple[int, int, int, int]], factory=set)
+    additions: Set[Tuple[int, int, int, int]] = attr.Factory(set)
 
     def add_link(
         self,
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
index a68f14ba..d5f00596 100644
--- a/synapse/storage/databases/main/events_bg_updates.py
+++ b/synapse/storage/databases/main/events_bg_updates.py
@@ -65,22 +65,22 @@ class _BackgroundUpdates:
     REPLACE_STREAM_ORDERING_COLUMN = "replace_stream_ordering_column"
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class _CalculateChainCover:
     """Return value for _calculate_chain_cover_txn."""
 
     # The last room_id/depth/stream processed.
-    room_id = attr.ib(type=str)
-    depth = attr.ib(type=int)
-    stream = attr.ib(type=int)
+    room_id: str
+    depth: int
+    stream: int
 
     # Number of rows processed
-    processed_count = attr.ib(type=int)
+    processed_count: int
 
     # Map from room_id to last depth/stream processed for each room that we have
     # processed all events for (i.e. the rooms we can flip the
     # `has_auth_chain_index` for)
-    finished_room_map = attr.ib(type=Dict[str, Tuple[int, int]])
+    finished_room_map: Dict[str, Tuple[int, int]]
 
 
 class EventsBackgroundUpdatesStore(SQLBaseStore):
@@ -684,13 +684,14 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
                     self.db_pool.simple_insert_many_txn(
                         txn=txn,
                         table="event_labels",
+                        keys=("event_id", "label", "room_id", "topological_ordering"),
                         values=[
-                            {
-                                "event_id": event_id,
-                                "label": label,
-                                "room_id": event_json["room_id"],
-                                "topological_ordering": event_json["depth"],
-                            }
+                            (
+                                event_id,
+                                label,
+                                event_json["room_id"],
+                                event_json["depth"],
+                            )
                             for label in event_json["content"].get(
                                 EventContentFields.LABELS, []
                             )
@@ -803,29 +804,19 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
 
             if not has_state:
                 state_events.append(
-                    {
-                        "event_id": event.event_id,
-                        "room_id": event.room_id,
-                        "type": event.type,
-                        "state_key": event.state_key,
-                    }
+                    (event.event_id, event.room_id, event.type, event.state_key)
                 )
 
             if not has_event_auth:
                 # Old, dodgy, events may have duplicate auth events, which we
                 # need to deduplicate as we have a unique constraint.
                 for auth_id in set(event.auth_event_ids()):
-                    auth_events.append(
-                        {
-                            "room_id": event.room_id,
-                            "event_id": event.event_id,
-                            "auth_id": auth_id,
-                        }
-                    )
+                    auth_events.append((event.event_id, event.room_id, auth_id))
 
         if state_events:
             await self.db_pool.simple_insert_many(
                 table="state_events",
+                keys=("event_id", "room_id", "type", "state_key"),
                 values=state_events,
                 desc="_rejected_events_metadata_state_events",
             )
@@ -833,6 +824,7 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
         if auth_events:
             await self.db_pool.simple_insert_many(
                 table="event_auth",
+                keys=("event_id", "room_id", "auth_id"),
                 values=auth_events,
                 desc="_rejected_events_metadata_event_auth",
             )
diff --git a/synapse/storage/databases/main/presence.py b/synapse/storage/databases/main/presence.py
index cbf9ec38..4f05811a 100644
--- a/synapse/storage/databases/main/presence.py
+++ b/synapse/storage/databases/main/presence.py
@@ -129,18 +129,29 @@ class PresenceStore(PresenceBackgroundUpdateStore):
         self.db_pool.simple_insert_many_txn(
             txn,
             table="presence_stream",
+            keys=(
+                "stream_id",
+                "user_id",
+                "state",
+                "last_active_ts",
+                "last_federation_update_ts",
+                "last_user_sync_ts",
+                "status_msg",
+                "currently_active",
+                "instance_name",
+            ),
             values=[
-                {
-                    "stream_id": stream_id,
-                    "user_id": state.user_id,
-                    "state": state.state,
-                    "last_active_ts": state.last_active_ts,
-                    "last_federation_update_ts": state.last_federation_update_ts,
-                    "last_user_sync_ts": state.last_user_sync_ts,
-                    "status_msg": state.status_msg,
-                    "currently_active": state.currently_active,
-                    "instance_name": self._instance_name,
-                }
+                (
+                    stream_id,
+                    state.user_id,
+                    state.state,
+                    state.last_active_ts,
+                    state.last_federation_update_ts,
+                    state.last_user_sync_ts,
+                    state.status_msg,
+                    state.currently_active,
+                    self._instance_name,
+                )
                 for stream_id, state in zip(stream_orderings, presence_states)
             ],
         )
diff --git a/synapse/storage/databases/main/pusher.py b/synapse/storage/databases/main/pusher.py
index 747b4f31..cf64cd63 100644
--- a/synapse/storage/databases/main/pusher.py
+++ b/synapse/storage/databases/main/pusher.py
@@ -561,13 +561,9 @@ class PusherStore(PusherWorkerStore):
             self.db_pool.simple_insert_many_txn(
                 txn,
                 table="deleted_pushers",
+                keys=("stream_id", "app_id", "pushkey", "user_id"),
                 values=[
-                    {
-                        "stream_id": stream_id,
-                        "app_id": pusher.app_id,
-                        "pushkey": pusher.pushkey,
-                        "user_id": user_id,
-                    }
+                    (stream_id, pusher.app_id, pusher.pushkey, user_id)
                     for stream_id, pusher in zip(stream_ids, pushers)
                 ],
             )
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 4175c82a..aac94fa4 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -51,7 +51,7 @@ class ExternalIDReuseException(Exception):
     pass
 
 
-@attr.s(frozen=True, slots=True)
+@attr.s(frozen=True, slots=True, auto_attribs=True)
 class TokenLookupResult:
     """Result of looking up an access token.
 
@@ -69,14 +69,14 @@ class TokenLookupResult:
             cached.
     """
 
-    user_id = attr.ib(type=str)
-    is_guest = attr.ib(type=bool, default=False)
-    shadow_banned = attr.ib(type=bool, default=False)
-    token_id = attr.ib(type=Optional[int], default=None)
-    device_id = attr.ib(type=Optional[str], default=None)
-    valid_until_ms = attr.ib(type=Optional[int], default=None)
-    token_owner = attr.ib(type=str)
-    token_used = attr.ib(type=bool, default=False)
+    user_id: str
+    is_guest: bool = False
+    shadow_banned: bool = False
+    token_id: Optional[int] = None
+    device_id: Optional[str] = None
+    valid_until_ms: Optional[int] = None
+    token_owner: str = attr.ib()
+    token_used: bool = False
 
     # Make the token owner default to the user ID, which is the common case.
     @token_owner.default
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 4ff6aed2..2cb5d06c 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -13,14 +13,30 @@
 # limitations under the License.
 
 import logging
-from typing import List, Optional, Tuple, Union, cast
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Tuple,
+    Union,
+    cast,
+)
 
 import attr
+from frozendict import frozendict
 
-from synapse.api.constants import RelationTypes
+from synapse.api.constants import EventTypes, RelationTypes
 from synapse.events import EventBase
 from synapse.storage._base import SQLBaseStore
-from synapse.storage.database import LoggingTransaction, make_in_list_sql_clause
+from synapse.storage.database import (
+    DatabasePool,
+    LoggingDatabaseConnection,
+    LoggingTransaction,
+    make_in_list_sql_clause,
+)
 from synapse.storage.databases.main.stream import generate_pagination_where_clause
 from synapse.storage.relations import (
     AggregationPaginationToken,
@@ -29,10 +45,24 @@ from synapse.storage.relations import (
 )
 from synapse.util.caches.descriptors import cached
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 class RelationsWorkerStore(SQLBaseStore):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ):
+        super().__init__(database, db_conn, hs)
+
+        self._msc1849_enabled = hs.config.experimental.msc1849_enabled
+        self._msc3440_enabled = hs.config.experimental.msc3440_enabled
+
     @cached(tree=True)
     async def get_relations_for_event(
         self,
@@ -354,8 +384,7 @@ class RelationsWorkerStore(SQLBaseStore):
     async def get_thread_summary(
         self, event_id: str, room_id: str
     ) -> Tuple[int, Optional[EventBase]]:
-        """Get the number of threaded replies, the senders of those replies, and
-        the latest reply (if any) for the given event.
+        """Get the number of threaded replies and the latest reply (if any) for the given event.
 
         Args:
             event_id: Summarize the thread related to this event ID.
@@ -368,7 +397,7 @@ class RelationsWorkerStore(SQLBaseStore):
         def _get_thread_summary_txn(
             txn: LoggingTransaction,
         ) -> Tuple[int, Optional[str]]:
-            # Fetch the count of threaded events and the latest event ID.
+            # Fetch the latest event ID in the thread.
             # TODO Should this only allow m.room.message events.
             sql = """
                 SELECT event_id
@@ -389,6 +418,7 @@ class RelationsWorkerStore(SQLBaseStore):
 
             latest_event_id = row[0]
 
+            # Fetch the number of threaded replies.
             sql = """
                 SELECT COUNT(event_id)
                 FROM event_relations
@@ -413,6 +443,44 @@ class RelationsWorkerStore(SQLBaseStore):
 
         return count, latest_event
 
+    @cached()
+    async def get_thread_participated(
+        self, event_id: str, room_id: str, user_id: str
+    ) -> bool:
+        """Get whether the requesting user participated in a thread.
+
+        This is separate from get_thread_summary since that can be cached across
+        all users while this value is specific to the requeser.
+
+        Args:
+            event_id: The thread related to this event ID.
+            room_id: The room the event belongs to.
+            user_id: The user requesting the summary.
+
+        Returns:
+            True if the requesting user participated in the thread, otherwise false.
+        """
+
+        def _get_thread_summary_txn(txn: LoggingTransaction) -> bool:
+            # Fetch whether the requester has participated or not.
+            sql = """
+                SELECT 1
+                FROM event_relations
+                INNER JOIN events USING (event_id)
+                WHERE
+                    relates_to_id = ?
+                    AND room_id = ?
+                    AND relation_type = ?
+                    AND sender = ?
+            """
+
+            txn.execute(sql, (event_id, room_id, RelationTypes.THREAD, user_id))
+            return bool(txn.fetchone())
+
+        return await self.db_pool.runInteraction(
+            "get_thread_summary", _get_thread_summary_txn
+        )
+
     async def events_have_relations(
         self,
         parent_ids: List[str],
@@ -515,6 +583,104 @@ class RelationsWorkerStore(SQLBaseStore):
             "get_if_user_has_annotated_event", _get_if_user_has_annotated_event
         )
 
+    async def _get_bundled_aggregation_for_event(
+        self, event: EventBase, user_id: str
+    ) -> Optional[Dict[str, Any]]:
+        """Generate bundled aggregations for an event.
+
+        Note that this does not use a cache, but depends on cached methods.
+
+        Args:
+            event: The event to calculate bundled aggregations for.
+            user_id: The user requesting the bundled aggregations.
+
+        Returns:
+            The bundled aggregations for an event, if bundled aggregations are
+            enabled and the event can have bundled aggregations.
+        """
+        # State events and redacted events do not get bundled aggregations.
+        if event.is_state() or event.internal_metadata.is_redacted():
+            return None
+
+        # Do not bundle aggregations for an event which represents an edit or an
+        # annotation. It does not make sense for them to have related events.
+        relates_to = event.content.get("m.relates_to")
+        if isinstance(relates_to, (dict, frozendict)):
+            relation_type = relates_to.get("rel_type")
+            if relation_type in (RelationTypes.ANNOTATION, RelationTypes.REPLACE):
+                return None
+
+        event_id = event.event_id
+        room_id = event.room_id
+
+        # The bundled aggregations to include, a mapping of relation type to a
+        # type-specific value. Some types include the direct return type here
+        # while others need more processing during serialization.
+        aggregations: Dict[str, Any] = {}
+
+        annotations = await self.get_aggregation_groups_for_event(event_id, room_id)
+        if annotations.chunk:
+            aggregations[RelationTypes.ANNOTATION] = annotations.to_dict()
+
+        references = await self.get_relations_for_event(
+            event_id, room_id, RelationTypes.REFERENCE, direction="f"
+        )
+        if references.chunk:
+            aggregations[RelationTypes.REFERENCE] = references.to_dict()
+
+        edit = None
+        if event.type == EventTypes.Message:
+            edit = await self.get_applicable_edit(event_id, room_id)
+
+        if edit:
+            aggregations[RelationTypes.REPLACE] = edit
+
+        # If this event is the start of a thread, include a summary of the replies.
+        if self._msc3440_enabled:
+            thread_count, latest_thread_event = await self.get_thread_summary(
+                event_id, room_id
+            )
+            participated = await self.get_thread_participated(
+                event_id, room_id, user_id
+            )
+            if latest_thread_event:
+                aggregations[RelationTypes.THREAD] = {
+                    "latest_event": latest_thread_event,
+                    "count": thread_count,
+                    "current_user_participated": participated,
+                }
+
+        # Store the bundled aggregations in the event metadata for later use.
+        return aggregations
+
+    async def get_bundled_aggregations(
+        self,
+        events: Iterable[EventBase],
+        user_id: str,
+    ) -> Dict[str, Dict[str, Any]]:
+        """Generate bundled aggregations for events.
+
+        Args:
+            events: The iterable of events to calculate bundled aggregations for.
+            user_id: The user requesting the bundled aggregations.
+
+        Returns:
+            A map of event ID to the bundled aggregation for the event. Not all
+            events may have bundled aggregations in the results.
+        """
+        # If bundled aggregations are disabled, nothing to do.
+        if not self._msc1849_enabled:
+            return {}
+
+        # TODO Parallelize.
+        results = {}
+        for event in events:
+            event_result = await self._get_bundled_aggregation_for_event(event, user_id)
+            if event_result is not None:
+                results[event.event_id] = event_result
+
+        return results
+
 
 class RelationsStore(RelationsWorkerStore):
     pass
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index c0e83785..95167116 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -551,24 +551,24 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
             FROM room_stats_state state
             INNER JOIN room_stats_current curr USING (room_id)
             INNER JOIN rooms USING (room_id)
-            %s
-            ORDER BY %s %s
+            {where}
+            ORDER BY {order_by} {direction}, state.room_id {direction}
             LIMIT ?
             OFFSET ?
-        """ % (
-            where_statement,
-            order_by_column,
-            "ASC" if order_by_asc else "DESC",
+        """.format(
+            where=where_statement,
+            order_by=order_by_column,
+            direction="ASC" if order_by_asc else "DESC",
         )
 
         # Use a nested SELECT statement as SQL can't count(*) with an OFFSET
         count_sql = """
             SELECT count(*) FROM (
               SELECT room_id FROM room_stats_state state
-              %s
+              {where}
             ) AS get_room_ids
-        """ % (
-            where_statement,
+        """.format(
+            where=where_statement,
         )
 
         def _get_rooms_paginate_txn(
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index cda80d65..4489732f 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -1177,18 +1177,18 @@ class RoomMemberStore(RoomMemberWorkerStore, RoomMemberBackgroundUpdateStore):
         await self.db_pool.runInteraction("forget_membership", f)
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _JoinedHostsCache:
     """The cached data used by the `_get_joined_hosts_cache`."""
 
     # Dict of host to the set of their users in the room at the state group.
-    hosts_to_joined_users = attr.ib(type=Dict[str, Set[str]], factory=dict)
+    hosts_to_joined_users: Dict[str, Set[str]] = attr.Factory(dict)
 
     # The state group `hosts_to_joined_users` is derived from. Will be an object
     # if the instance is newly created or if the state is not based on a state
     # group. (An object is used as a sentinel value to ensure that it never is
     # equal to anything else).
-    state_group = attr.ib(type=Union[object, int], factory=object)
+    state_group: Union[object, int] = attr.Factory(object)
 
     def __len__(self):
         return sum(len(v) for v in self.hosts_to_joined_users.values())
diff --git a/synapse/storage/databases/main/session.py b/synapse/storage/databases/main/session.py
index 5a971204..e8c776b9 100644
--- a/synapse/storage/databases/main/session.py
+++ b/synapse/storage/databases/main/session.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 #  Copyright 2021 The Matrix.org Foundation C.I.C.
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/synapse/storage/databases/main/transactions.py b/synapse/storage/databases/main/transactions.py
index 6c299caf..4b78b4d0 100644
--- a/synapse/storage/databases/main/transactions.py
+++ b/synapse/storage/databases/main/transactions.py
@@ -560,3 +560,14 @@ class TransactionWorkerStore(CacheInvalidationWorkerStore):
         return await self.db_pool.runInteraction(
             "get_destinations_paginate_txn", get_destinations_paginate_txn
         )
+
+    async def is_destination_known(self, destination: str) -> bool:
+        """Check if a destination is known to the server."""
+        result = await self.db_pool.simple_select_one_onecol(
+            table="destinations",
+            keyvalues={"destination": destination},
+            retcol="1",
+            allow_none=True,
+            desc="is_destination_known",
+        )
+        return bool(result)
diff --git a/synapse/storage/databases/main/ui_auth.py b/synapse/storage/databases/main/ui_auth.py
index a1a1a6a1..2d339b60 100644
--- a/synapse/storage/databases/main/ui_auth.py
+++ b/synapse/storage/databases/main/ui_auth.py
@@ -23,19 +23,19 @@ from synapse.types import JsonDict
 from synapse.util import json_encoder, stringutils
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class UIAuthSessionData:
-    session_id = attr.ib(type=str)
+    session_id: str
     # The dictionary from the client root level, not the 'auth' key.
-    clientdict = attr.ib(type=JsonDict)
+    clientdict: JsonDict
     # The URI and method the session was intiatied with. These are checked at
     # each stage of the authentication to ensure that the asked for operation
     # has not changed.
-    uri = attr.ib(type=str)
-    method = attr.ib(type=str)
+    uri: str
+    method: str
     # A string description of the operation that the current authentication is
     # authorising.
-    description = attr.ib(type=str)
+    description: str
 
 
 class UIAuthWorkerStore(SQLBaseStore):
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
index 0f9b8575..f7c778bd 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -105,8 +105,10 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
                 GROUP BY room_id
             """
             txn.execute(sql)
-            rooms = [{"room_id": x[0], "events": x[1]} for x in txn.fetchall()]
-            self.db_pool.simple_insert_many_txn(txn, TEMP_TABLE + "_rooms", rooms)
+            rooms = list(txn.fetchall())
+            self.db_pool.simple_insert_many_txn(
+                txn, TEMP_TABLE + "_rooms", keys=("room_id", "events"), values=rooms
+            )
             del rooms
 
             sql = (
@@ -117,9 +119,11 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
             txn.execute(sql)
 
             txn.execute("SELECT name FROM users")
-            users = [{"user_id": x[0]} for x in txn.fetchall()]
+            users = list(txn.fetchall())
 
-            self.db_pool.simple_insert_many_txn(txn, TEMP_TABLE + "_users", users)
+            self.db_pool.simple_insert_many_txn(
+                txn, TEMP_TABLE + "_users", keys=("user_id",), values=users
+            )
 
         new_pos = await self.get_max_stream_id_in_current_state_deltas()
         await self.db_pool.runInteraction(
diff --git a/synapse/storage/databases/state/bg_updates.py b/synapse/storage/databases/state/bg_updates.py
index eb1118d2..5de70f31 100644
--- a/synapse/storage/databases/state/bg_updates.py
+++ b/synapse/storage/databases/state/bg_updates.py
@@ -327,14 +327,15 @@ class StateBackgroundUpdateStore(StateGroupBackgroundUpdateStore):
                         self.db_pool.simple_insert_many_txn(
                             txn,
                             table="state_groups_state",
+                            keys=(
+                                "state_group",
+                                "room_id",
+                                "type",
+                                "state_key",
+                                "event_id",
+                            ),
                             values=[
-                                {
-                                    "state_group": state_group,
-                                    "room_id": room_id,
-                                    "type": key[0],
-                                    "state_key": key[1],
-                                    "event_id": state_id,
-                                }
+                                (state_group, room_id, key[0], key[1], state_id)
                                 for key, state_id in delta_state.items()
                             ],
                         )
diff --git a/synapse/storage/databases/state/store.py b/synapse/storage/databases/state/store.py
index c4c8c002..7614d76a 100644
--- a/synapse/storage/databases/state/store.py
+++ b/synapse/storage/databases/state/store.py
@@ -460,14 +460,9 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
                 self.db_pool.simple_insert_many_txn(
                     txn,
                     table="state_groups_state",
+                    keys=("state_group", "room_id", "type", "state_key", "event_id"),
                     values=[
-                        {
-                            "state_group": state_group,
-                            "room_id": room_id,
-                            "type": key[0],
-                            "state_key": key[1],
-                            "event_id": state_id,
-                        }
+                        (state_group, room_id, key[0], key[1], state_id)
                         for key, state_id in delta_ids.items()
                     ],
                 )
@@ -475,14 +470,9 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
                 self.db_pool.simple_insert_many_txn(
                     txn,
                     table="state_groups_state",
+                    keys=("state_group", "room_id", "type", "state_key", "event_id"),
                     values=[
-                        {
-                            "state_group": state_group,
-                            "room_id": room_id,
-                            "type": key[0],
-                            "state_key": key[1],
-                            "event_id": state_id,
-                        }
+                        (state_group, room_id, key[0], key[1], state_id)
                         for key, state_id in current_state_ids.items()
                     ],
                 )
@@ -589,14 +579,9 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
             self.db_pool.simple_insert_many_txn(
                 txn,
                 table="state_groups_state",
+                keys=("state_group", "room_id", "type", "state_key", "event_id"),
                 values=[
-                    {
-                        "state_group": sg,
-                        "room_id": room_id,
-                        "type": key[0],
-                        "state_key": key[1],
-                        "event_id": state_id,
-                    }
+                    (sg, room_id, key[0], key[1], state_id)
                     for key, state_id in curr_state.items()
                 ],
             )
diff --git a/synapse/storage/keys.py b/synapse/storage/keys.py
index 540adb87..71584f3f 100644
--- a/synapse/storage/keys.py
+++ b/synapse/storage/keys.py
@@ -21,7 +21,7 @@ from signedjson.types import VerifyKey
 logger = logging.getLogger(__name__)
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class FetchKeyResult:
-    verify_key = attr.ib(type=VerifyKey)  # the key itself
-    valid_until_ts = attr.ib(type=int)  # how long we can use this key for
+    verify_key: VerifyKey  # the key itself
+    valid_until_ts: int  # how long we can use this key for
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index e45adfcb..1823e187 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -696,7 +696,7 @@ def _get_or_create_schema_state(
     )
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _DirectoryListing:
     """Helper class to store schema file name and the
     absolute path to it.
@@ -705,5 +705,5 @@ class _DirectoryListing:
     `file_name` attr is kept first.
     """
 
-    file_name = attr.ib(type=str)
-    absolute_path = attr.ib(type=str)
+    file_name: str
+    absolute_path: str
diff --git a/synapse/storage/relations.py b/synapse/storage/relations.py
index 10a46b5e..b1536c1c 100644
--- a/synapse/storage/relations.py
+++ b/synapse/storage/relations.py
@@ -23,7 +23,7 @@ from synapse.types import JsonDict
 logger = logging.getLogger(__name__)
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class PaginationChunk:
     """Returned by relation pagination APIs.
 
@@ -35,9 +35,9 @@ class PaginationChunk:
             None then there are no previous results.
     """
 
-    chunk = attr.ib(type=List[JsonDict])
-    next_batch = attr.ib(type=Optional[Any], default=None)
-    prev_batch = attr.ib(type=Optional[Any], default=None)
+    chunk: List[JsonDict]
+    next_batch: Optional[Any] = None
+    prev_batch: Optional[Any] = None
 
     def to_dict(self) -> Dict[str, Any]:
         d = {"chunk": self.chunk}
@@ -51,7 +51,7 @@ class PaginationChunk:
         return d
 
 
-@attr.s(frozen=True, slots=True)
+@attr.s(frozen=True, slots=True, auto_attribs=True)
 class RelationPaginationToken:
     """Pagination token for relation pagination API.
 
@@ -64,8 +64,8 @@ class RelationPaginationToken:
         stream: The stream ordering of the boundary event.
     """
 
-    topological = attr.ib(type=int)
-    stream = attr.ib(type=int)
+    topological: int
+    stream: int
 
     @staticmethod
     def from_string(string: str) -> "RelationPaginationToken":
@@ -82,7 +82,7 @@ class RelationPaginationToken:
         return attr.astuple(self)
 
 
-@attr.s(frozen=True, slots=True)
+@attr.s(frozen=True, slots=True, auto_attribs=True)
 class AggregationPaginationToken:
     """Pagination token for relation aggregation pagination API.
 
@@ -94,8 +94,8 @@ class AggregationPaginationToken:
         stream: The MAX stream ordering in the boundary group.
     """
 
-    count = attr.ib(type=int)
-    stream = attr.ib(type=int)
+    count: int
+    stream: int
 
     @staticmethod
     def from_string(string: str) -> "AggregationPaginationToken":
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index b5ba1560..df8b2f10 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -45,7 +45,7 @@ logger = logging.getLogger(__name__)
 T = TypeVar("T")
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class StateFilter:
     """A filter used when querying for state.
 
@@ -58,8 +58,8 @@ class StateFilter:
             appear in `types`.
     """
 
-    types = attr.ib(type="frozendict[str, Optional[FrozenSet[str]]]")
-    include_others = attr.ib(default=False, type=bool)
+    types: "frozendict[str, Optional[FrozenSet[str]]]"
+    include_others: bool = False
 
     def __attrs_post_init__(self):
         # If `include_others` is set we canonicalise the filter by removing
diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index b8112e1c..3c13859f 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -762,13 +762,13 @@ class _AsyncCtxManagerWrapper(Generic[T]):
         return self.inner.__exit__(exc_type, exc, tb)
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _MultiWriterCtxManager:
     """Async context manager returned by MultiWriterIdGenerator"""
 
-    id_gen = attr.ib(type=MultiWriterIdGenerator)
-    multiple_ids = attr.ib(type=Optional[int], default=None)
-    stream_ids = attr.ib(type=List[int], factory=list)
+    id_gen: MultiWriterIdGenerator
+    multiple_ids: Optional[int] = None
+    stream_ids: List[int] = attr.Factory(list)
 
     async def __aenter__(self) -> Union[int, List[int]]:
         # It's safe to run this in autocommit mode as fetching values from a
diff --git a/synapse/streams/config.py b/synapse/streams/config.py
index c08d591f..b52723e2 100644
--- a/synapse/streams/config.py
+++ b/synapse/streams/config.py
@@ -28,14 +28,14 @@ logger = logging.getLogger(__name__)
 MAX_LIMIT = 1000
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class PaginationConfig:
     """A configuration object which stores pagination parameters."""
 
-    from_token = attr.ib(type=Optional[StreamToken])
-    to_token = attr.ib(type=Optional[StreamToken])
-    direction = attr.ib(type=str)
-    limit = attr.ib(type=Optional[int])
+    from_token: Optional[StreamToken]
+    to_token: Optional[StreamToken]
+    direction: str
+    limit: Optional[int]
 
     @classmethod
     async def from_request(
diff --git a/synapse/types.py b/synapse/types.py
index 42aeaf62..f89fb216 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -20,7 +20,9 @@ from typing import (
     Any,
     ClassVar,
     Dict,
+    List,
     Mapping,
+    Match,
     MutableMapping,
     Optional,
     Tuple,
@@ -79,7 +81,7 @@ class ISynapseReactor(
     """The interfaces necessary for Synapse to function."""
 
 
-@attr.s(frozen=True, slots=True)
+@attr.s(frozen=True, slots=True, auto_attribs=True)
 class Requester:
     """
     Represents the user making a request
@@ -97,13 +99,13 @@ class Requester:
             "puppeting" the user.
     """
 
-    user = attr.ib(type="UserID")
-    access_token_id = attr.ib(type=Optional[int])
-    is_guest = attr.ib(type=bool)
-    shadow_banned = attr.ib(type=bool)
-    device_id = attr.ib(type=Optional[str])
-    app_service = attr.ib(type=Optional["ApplicationService"])
-    authenticated_entity = attr.ib(type=str)
+    user: "UserID"
+    access_token_id: Optional[int]
+    is_guest: bool
+    shadow_banned: bool
+    device_id: Optional[str]
+    app_service: Optional["ApplicationService"]
+    authenticated_entity: str
 
     def serialize(self):
         """Converts self to a type that can be serialized as JSON, and then
@@ -210,7 +212,7 @@ def get_localpart_from_id(string: str) -> str:
 DS = TypeVar("DS", bound="DomainSpecificString")
 
 
-@attr.s(slots=True, frozen=True, repr=False)
+@attr.s(slots=True, frozen=True, repr=False, auto_attribs=True)
 class DomainSpecificString(metaclass=abc.ABCMeta):
     """Common base class among ID/name strings that have a local part and a
     domain name, prefixed with a sigil.
@@ -223,8 +225,8 @@ class DomainSpecificString(metaclass=abc.ABCMeta):
 
     SIGIL: ClassVar[str] = abc.abstractproperty()  # type: ignore
 
-    localpart = attr.ib(type=str)
-    domain = attr.ib(type=str)
+    localpart: str
+    domain: str
 
     # Because this is a frozen class, it is deeply immutable.
     def __copy__(self):
@@ -380,7 +382,7 @@ def map_username_to_mxid_localpart(
             onto different mxids
 
     Returns:
-        unicode: string suitable for a mxid localpart
+        string suitable for a mxid localpart
     """
     if not isinstance(username, bytes):
         username = username.encode("utf-8")
@@ -388,29 +390,23 @@ def map_username_to_mxid_localpart(
     # first we sort out upper-case characters
     if case_sensitive:
 
-        def f1(m):
+        def f1(m: Match[bytes]) -> bytes:
             return b"_" + m.group().lower()
 
         username = UPPER_CASE_PATTERN.sub(f1, username)
     else:
         username = username.lower()
 
-    # then we sort out non-ascii characters
-    def f2(m):
-        g = m.group()[0]
-        if isinstance(g, str):
-            # on python 2, we need to do a ord(). On python 3, the
-            # byte itself will do.
-            g = ord(g)
-        return b"=%02x" % (g,)
+    # then we sort out non-ascii characters by converting to the hex equivalent.
+    def f2(m: Match[bytes]) -> bytes:
+        return b"=%02x" % (m.group()[0],)
 
     username = NON_MXID_CHARACTER_PATTERN.sub(f2, username)
 
     # we also do the =-escaping to mxids starting with an underscore.
     username = re.sub(b"^_", b"=5f", username)
 
-    # we should now only have ascii bytes left, so can decode back to a
-    # unicode.
+    # we should now only have ascii bytes left, so can decode back to a string.
     return username.decode("ascii")
 
 
@@ -466,14 +462,12 @@ class RoomStreamToken:
     attributes, must be hashable.
     """
 
-    topological = attr.ib(
-        type=Optional[int],
+    topological: Optional[int] = attr.ib(
         validator=attr.validators.optional(attr.validators.instance_of(int)),
     )
-    stream = attr.ib(type=int, validator=attr.validators.instance_of(int))
+    stream: int = attr.ib(validator=attr.validators.instance_of(int))
 
-    instance_map = attr.ib(
-        type="frozendict[str, int]",
+    instance_map: "frozendict[str, int]" = attr.ib(
         factory=frozendict,
         validator=attr.validators.deep_mapping(
             key_validator=attr.validators.instance_of(str),
@@ -482,7 +476,7 @@ class RoomStreamToken:
         ),
     )
 
-    def __attrs_post_init__(self):
+    def __attrs_post_init__(self) -> None:
         """Validates that both `topological` and `instance_map` aren't set."""
 
         if self.instance_map and self.topological:
@@ -598,7 +592,7 @@ class RoomStreamToken:
             return "s%d" % (self.stream,)
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class StreamToken:
     """A collection of positions within multiple streams.
 
@@ -606,20 +600,20 @@ class StreamToken:
     must be hashable.
     """
 
-    room_key = attr.ib(
-        type=RoomStreamToken, validator=attr.validators.instance_of(RoomStreamToken)
+    room_key: RoomStreamToken = attr.ib(
+        validator=attr.validators.instance_of(RoomStreamToken)
     )
-    presence_key = attr.ib(type=int)
-    typing_key = attr.ib(type=int)
-    receipt_key = attr.ib(type=int)
-    account_data_key = attr.ib(type=int)
-    push_rules_key = attr.ib(type=int)
-    to_device_key = attr.ib(type=int)
-    device_list_key = attr.ib(type=int)
-    groups_key = attr.ib(type=int)
+    presence_key: int
+    typing_key: int
+    receipt_key: int
+    account_data_key: int
+    push_rules_key: int
+    to_device_key: int
+    device_list_key: int
+    groups_key: int
 
     _SEPARATOR = "_"
-    START: "StreamToken"
+    START: ClassVar["StreamToken"]
 
     @classmethod
     async def from_string(cls, store: "DataStore", string: str) -> "StreamToken":
@@ -679,7 +673,7 @@ class StreamToken:
 StreamToken.START = StreamToken(RoomStreamToken(None, 0), 0, 0, 0, 0, 0, 0, 0, 0)
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class PersistedEventPosition:
     """Position of a newly persisted event with instance that persisted it.
 
@@ -687,8 +681,8 @@ class PersistedEventPosition:
     RoomStreamToken.
     """
 
-    instance_name = attr.ib(type=str)
-    stream = attr.ib(type=int)
+    instance_name: str
+    stream: int
 
     def persisted_after(self, token: RoomStreamToken) -> bool:
         return token.get_stream_pos_for_instance(self.instance_name) < self.stream
@@ -738,15 +732,15 @@ class ThirdPartyInstanceID:
     __str__ = to_string
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class ReadReceipt:
     """Information about a read-receipt"""
 
-    room_id = attr.ib()
-    receipt_type = attr.ib()
-    user_id = attr.ib()
-    event_ids = attr.ib()
-    data = attr.ib()
+    room_id: str
+    receipt_type: str
+    user_id: str
+    event_ids: List[str]
+    data: JsonDict
 
 
 def get_verify_key_from_cross_signing_key(key_info):
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 150a04b5..3f7299af 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -309,12 +309,12 @@ def gather_results(  # type: ignore[misc]
     return deferred.addCallback(tuple)
 
 
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class _LinearizerEntry:
     # The number of things executing.
-    count = attr.ib(type=int)
+    count: int
     # Deferreds for the things blocked from executing.
-    deferreds = attr.ib(type=collections.OrderedDict)
+    deferreds: collections.OrderedDict
 
 
 class Linearizer:
diff --git a/synapse/util/caches/dictionary_cache.py b/synapse/util/caches/dictionary_cache.py
index 485ddb18..d267703d 100644
--- a/synapse/util/caches/dictionary_cache.py
+++ b/synapse/util/caches/dictionary_cache.py
@@ -33,7 +33,7 @@ DV = TypeVar("DV")
 
 # This class can't be generic because it uses slots with attrs.
 # See: https://github.com/python-attrs/attrs/issues/313
-@attr.s(slots=True)
+@attr.s(slots=True, auto_attribs=True)
 class DictionaryEntry:  # should be: Generic[DKT, DV].
     """Returned when getting an entry from the cache
 
@@ -41,14 +41,13 @@ class DictionaryEntry:  # should be: Generic[DKT, DV].
         full: Whether the cache has the full or dict or just some keys.
             If not full then not all requested keys will necessarily be present
             in `value`
-        known_absent: Keys that were looked up in the dict and were not
-            there.
+        known_absent: Keys that were looked up in the dict and were not there.
         value: The full or partial dict value
     """
 
-    full = attr.ib(type=bool)
-    known_absent = attr.ib(type=Set[Any])  # should be: Set[DKT]
-    value = attr.ib(type=Dict[Any, Any])  # should be: Dict[DKT, DV]
+    full: bool
+    known_absent: Set[Any]  # should be: Set[DKT]
+    value: Dict[Any, Any]  # should be: Dict[DKT, DV]
 
     def __len__(self) -> int:
         return len(self.value)
diff --git a/tests/api/test_auth.py b/tests/api/test_auth.py
index a2dfa1ed..4b53b6d4 100644
--- a/tests/api/test_auth.py
+++ b/tests/api/test_auth.py
@@ -274,6 +274,39 @@ class AuthTestCase(unittest.HomeserverTestCase):
         self.assertEquals(failure.value.code, 400)
         self.assertEquals(failure.value.errcode, Codes.EXCLUSIVE)
 
+    def test_get_user_by_req__puppeted_token__not_tracking_puppeted_mau(self):
+        self.store.get_user_by_access_token = simple_async_mock(
+            TokenLookupResult(
+                user_id="@baldrick:matrix.org",
+                device_id="device",
+                token_owner="@admin:matrix.org",
+            )
+        )
+        self.store.insert_client_ip = simple_async_mock(None)
+        request = Mock(args={})
+        request.getClientIP.return_value = "127.0.0.1"
+        request.args[b"access_token"] = [self.test_token]
+        request.requestHeaders.getRawHeaders = mock_getRawHeaders()
+        self.get_success(self.auth.get_user_by_req(request))
+        self.store.insert_client_ip.assert_called_once()
+
+    def test_get_user_by_req__puppeted_token__tracking_puppeted_mau(self):
+        self.auth._track_puppeted_user_ips = True
+        self.store.get_user_by_access_token = simple_async_mock(
+            TokenLookupResult(
+                user_id="@baldrick:matrix.org",
+                device_id="device",
+                token_owner="@admin:matrix.org",
+            )
+        )
+        self.store.insert_client_ip = simple_async_mock(None)
+        request = Mock(args={})
+        request.getClientIP.return_value = "127.0.0.1"
+        request.args[b"access_token"] = [self.test_token]
+        request.requestHeaders.getRawHeaders = mock_getRawHeaders()
+        self.get_success(self.auth.get_user_by_req(request))
+        self.assertEquals(self.store.insert_client_ip.call_count, 2)
+
     def test_get_user_from_macaroon(self):
         self.store.get_user_by_access_token = simple_async_mock(
             TokenLookupResult(user_id="@baldrick:matrix.org", device_id="device")
diff --git a/tests/handlers/test_e2e_keys.py b/tests/handlers/test_e2e_keys.py
index ddcf3ee3..734ed84d 100644
--- a/tests/handlers/test_e2e_keys.py
+++ b/tests/handlers/test_e2e_keys.py
@@ -13,8 +13,10 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from typing import Iterable
 from unittest import mock
 
+from parameterized import parameterized
 from signedjson import key as key, sign as sign
 
 from twisted.internet import defer
@@ -23,6 +25,7 @@ from synapse.api.constants import RoomEncryptionAlgorithms
 from synapse.api.errors import Codes, SynapseError
 
 from tests import unittest
+from tests.test_utils import make_awaitable
 
 
 class E2eKeysHandlerTestCase(unittest.HomeserverTestCase):
@@ -765,6 +768,8 @@ class E2eKeysHandlerTestCase(unittest.HomeserverTestCase):
         remote_user_id = "@test:other"
         local_user_id = "@test:test"
 
+        # Pretend we're sharing a room with the user we're querying. If not,
+        # `_query_devices_for_destination` will return early.
         self.store.get_rooms_for_user = mock.Mock(
             return_value=defer.succeed({"some_room_id"})
         )
@@ -831,3 +836,94 @@ class E2eKeysHandlerTestCase(unittest.HomeserverTestCase):
                 }
             },
         )
+
+    @parameterized.expand(
+        [
+            # The remote homeserver's response indicates that this user has 0/1/2 devices.
+            ([],),
+            (["device_1"],),
+            (["device_1", "device_2"],),
+        ]
+    )
+    def test_query_all_devices_caches_result(self, device_ids: Iterable[str]):
+        """Test that requests for all of a remote user's devices are cached.
+
+        We do this by asserting that only one call over federation was made, and that
+        the two queries to the local homeserver produce the same response.
+        """
+        local_user_id = "@test:test"
+        remote_user_id = "@test:other"
+        request_body = {"device_keys": {remote_user_id: []}}
+
+        response_devices = [
+            {
+                "device_id": device_id,
+                "keys": {
+                    "algorithms": ["dummy"],
+                    "device_id": device_id,
+                    "keys": {f"dummy:{device_id}": "dummy"},
+                    "signatures": {device_id: {f"dummy:{device_id}": "dummy"}},
+                    "unsigned": {},
+                    "user_id": "@test:other",
+                },
+            }
+            for device_id in device_ids
+        ]
+
+        response_body = {
+            "devices": response_devices,
+            "user_id": remote_user_id,
+            "stream_id": 12345,  # an integer, according to the spec
+        }
+
+        e2e_handler = self.hs.get_e2e_keys_handler()
+
+        # Pretend we're sharing a room with the user we're querying. If not,
+        # `_query_devices_for_destination` will return early.
+        mock_get_rooms = mock.patch.object(
+            self.store,
+            "get_rooms_for_user",
+            new_callable=mock.MagicMock,
+            return_value=make_awaitable(["some_room_id"]),
+        )
+        mock_request = mock.patch.object(
+            self.hs.get_federation_client(),
+            "query_user_devices",
+            new_callable=mock.MagicMock,
+            return_value=make_awaitable(response_body),
+        )
+
+        with mock_get_rooms, mock_request as mocked_federation_request:
+            # Make the first query and sanity check it succeeds.
+            response_1 = self.get_success(
+                e2e_handler.query_devices(
+                    request_body,
+                    timeout=10,
+                    from_user_id=local_user_id,
+                    from_device_id="some_device_id",
+                )
+            )
+            self.assertEqual(response_1["failures"], {})
+
+            # We should have made a federation request to do so.
+            mocked_federation_request.assert_called_once()
+
+            # Reset the mock so we can prove we don't make a second federation request.
+            mocked_federation_request.reset_mock()
+
+            # Repeat the query.
+            response_2 = self.get_success(
+                e2e_handler.query_devices(
+                    request_body,
+                    timeout=10,
+                    from_user_id=local_user_id,
+                    from_device_id="some_device_id",
+                )
+            )
+            self.assertEqual(response_2["failures"], {})
+
+            # We should not have made a second federation request.
+            mocked_federation_request.assert_not_called()
+
+            # The two requests to the local homeserver should be identical.
+            self.assertEqual(response_1, response_2)
diff --git a/tests/handlers/test_password_providers.py b/tests/handlers/test_password_providers.py
index 08e9730d..2add72b2 100644
--- a/tests/handlers/test_password_providers.py
+++ b/tests/handlers/test_password_providers.py
@@ -22,7 +22,7 @@ from twisted.internet import defer
 import synapse
 from synapse.handlers.auth import load_legacy_password_auth_providers
 from synapse.module_api import ModuleApi
-from synapse.rest.client import devices, login
+from synapse.rest.client import devices, login, logout
 from synapse.types import JsonDict
 
 from tests import unittest
@@ -155,6 +155,7 @@ class PasswordAuthProviderTests(unittest.HomeserverTestCase):
         synapse.rest.admin.register_servlets,
         login.register_servlets,
         devices.register_servlets,
+        logout.register_servlets,
     ]
 
     def setUp(self):
@@ -719,6 +720,31 @@ class PasswordAuthProviderTests(unittest.HomeserverTestCase):
         channel = self._send_password_login("localuser", "localpass")
         self.assertEqual(channel.code, 400, channel.result)
 
+    def test_on_logged_out(self):
+        """Tests that the on_logged_out callback is called when the user logs out."""
+        self.register_user("rin", "password")
+        tok = self.login("rin", "password")
+
+        self.called = False
+
+        async def on_logged_out(user_id, device_id, access_token):
+            self.called = True
+
+        on_logged_out = Mock(side_effect=on_logged_out)
+        self.hs.get_password_auth_provider().on_logged_out_callbacks.append(
+            on_logged_out
+        )
+
+        channel = self.make_request(
+            "POST",
+            "/_matrix/client/v3/logout",
+            {},
+            access_token=tok,
+        )
+        self.assertEqual(channel.code, 200)
+        on_logged_out.assert_called_once()
+        self.assertTrue(self.called)
+
     def _get_login_flows(self) -> JsonDict:
         channel = self.make_request("GET", "/_matrix/client/r0/login")
         self.assertEqual(channel.code, 200, channel.result)
diff --git a/tests/handlers/test_room_summary.py b/tests/handlers/test_room_summary.py
index e5a6a6c7..51b22d29 100644
--- a/tests/handlers/test_room_summary.py
+++ b/tests/handlers/test_room_summary.py
@@ -28,6 +28,7 @@ from synapse.api.constants import (
 from synapse.api.errors import AuthError, NotFoundError, SynapseError
 from synapse.api.room_versions import RoomVersions
 from synapse.events import make_event_from_dict
+from synapse.federation.transport.client import TransportLayerClient
 from synapse.handlers.room_summary import _child_events_comparison_key, _RoomEntry
 from synapse.rest import admin
 from synapse.rest.client import login, room
@@ -134,10 +135,18 @@ class SpaceSummaryTestCase(unittest.HomeserverTestCase):
         self._add_child(self.space, self.room, self.token)
 
     def _add_child(
-        self, space_id: str, room_id: str, token: str, order: Optional[str] = None
+        self,
+        space_id: str,
+        room_id: str,
+        token: str,
+        order: Optional[str] = None,
+        via: Optional[List[str]] = None,
     ) -> None:
         """Add a child room to a space."""
-        content: JsonDict = {"via": [self.hs.hostname]}
+        if via is None:
+            via = [self.hs.hostname]
+
+        content: JsonDict = {"via": via}
         if order is not None:
             content["order"] = order
         self.helper.send_state(
@@ -253,6 +262,38 @@ class SpaceSummaryTestCase(unittest.HomeserverTestCase):
         )
         self._assert_hierarchy(result, expected)
 
+    def test_large_space(self):
+        """Test a space with a large number of rooms."""
+        rooms = [self.room]
+        # Make at least 51 rooms that are part of the space.
+        for _ in range(55):
+            room = self.helper.create_room_as(self.user, tok=self.token)
+            self._add_child(self.space, room, self.token)
+            rooms.append(room)
+
+        result = self.get_success(self.handler.get_space_summary(self.user, self.space))
+        # The spaces result should have the space and the first 50 rooms in it,
+        # along with the links from space -> room for those 50 rooms.
+        expected = [(self.space, rooms[:50])] + [(room, []) for room in rooms[:49]]
+        self._assert_rooms(result, expected)
+
+        # The result should have the space and the rooms in it, along with the links
+        # from space -> room.
+        expected = [(self.space, rooms)] + [(room, []) for room in rooms]
+
+        # Make two requests to fully paginate the results.
+        result = self.get_success(
+            self.handler.get_room_hierarchy(create_requester(self.user), self.space)
+        )
+        result2 = self.get_success(
+            self.handler.get_room_hierarchy(
+                create_requester(self.user), self.space, from_token=result["next_batch"]
+            )
+        )
+        # Combine the results.
+        result["rooms"] += result2["rooms"]
+        self._assert_hierarchy(result, expected)
+
     def test_visibility(self):
         """A user not in a space cannot inspect it."""
         user2 = self.register_user("user2", "pass")
@@ -1004,6 +1045,85 @@ class SpaceSummaryTestCase(unittest.HomeserverTestCase):
             )
         self._assert_hierarchy(result, expected)
 
+    def test_fed_caching(self):
+        """
+        Federation `/hierarchy` responses should be cached.
+        """
+        fed_hostname = self.hs.hostname + "2"
+        fed_subspace = "#space:" + fed_hostname
+        fed_room = "#room:" + fed_hostname
+
+        # Add a room to the space which is on another server.
+        self._add_child(self.space, fed_subspace, self.token, via=[fed_hostname])
+
+        federation_requests = 0
+
+        async def get_room_hierarchy(
+            _self: TransportLayerClient,
+            destination: str,
+            room_id: str,
+            suggested_only: bool,
+        ) -> JsonDict:
+            nonlocal federation_requests
+            federation_requests += 1
+
+            return {
+                "room": {
+                    "room_id": fed_subspace,
+                    "world_readable": True,
+                    "room_type": RoomTypes.SPACE,
+                    "children_state": [
+                        {
+                            "type": EventTypes.SpaceChild,
+                            "room_id": fed_subspace,
+                            "state_key": fed_room,
+                            "content": {"via": [fed_hostname]},
+                        },
+                    ],
+                },
+                "children": [
+                    {
+                        "room_id": fed_room,
+                        "world_readable": True,
+                    },
+                ],
+                "inaccessible_children": [],
+            }
+
+        expected = [
+            (self.space, [self.room, fed_subspace]),
+            (self.room, ()),
+            (fed_subspace, [fed_room]),
+            (fed_room, ()),
+        ]
+
+        with mock.patch(
+            "synapse.federation.transport.client.TransportLayerClient.get_room_hierarchy",
+            new=get_room_hierarchy,
+        ):
+            result = self.get_success(
+                self.handler.get_room_hierarchy(create_requester(self.user), self.space)
+            )
+            self.assertEqual(federation_requests, 1)
+            self._assert_hierarchy(result, expected)
+
+            # The previous federation response should be reused.
+            result = self.get_success(
+                self.handler.get_room_hierarchy(create_requester(self.user), self.space)
+            )
+            self.assertEqual(federation_requests, 1)
+            self._assert_hierarchy(result, expected)
+
+            # Expire the response cache
+            self.reactor.advance(5 * 60 + 1)
+
+            # A new federation request should be made.
+            result = self.get_success(
+                self.handler.get_room_hierarchy(create_requester(self.user), self.space)
+            )
+            self.assertEqual(federation_requests, 2)
+            self._assert_hierarchy(result, expected)
+
 
 class RoomSummaryTestCase(unittest.HomeserverTestCase):
     servlets = [
diff --git a/tests/handlers/test_sync.py b/tests/handlers/test_sync.py
index 638186f1..07a760e9 100644
--- a/tests/handlers/test_sync.py
+++ b/tests/handlers/test_sync.py
@@ -11,15 +11,14 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 from typing import Optional
-from unittest.mock import Mock
+from unittest.mock import MagicMock, Mock, patch
 
 from synapse.api.constants import EventTypes, JoinRules
 from synapse.api.errors import Codes, ResourceLimitError
 from synapse.api.filtering import Filtering
 from synapse.api.room_versions import RoomVersions
-from synapse.handlers.sync import SyncConfig
+from synapse.handlers.sync import SyncConfig, SyncResult
 from synapse.rest import admin
 from synapse.rest.client import knock, login, room
 from synapse.server import HomeServer
@@ -27,6 +26,7 @@ from synapse.types import UserID, create_requester
 
 import tests.unittest
 import tests.utils
+from tests.test_utils import make_awaitable
 
 
 class SyncTestCase(tests.unittest.HomeserverTestCase):
@@ -186,6 +186,97 @@ class SyncTestCase(tests.unittest.HomeserverTestCase):
         self.assertNotIn(invite_room, [r.room_id for r in result.invited])
         self.assertNotIn(knock_room, [r.room_id for r in result.knocked])
 
+    def test_ban_wins_race_with_join(self):
+        """Rooms shouldn't appear under "joined" if a join loses a race to a ban.
+
+        A complicated edge case. Imagine the following scenario:
+
+        * you attempt to join a room
+        * racing with that is a ban which comes in over federation, which ends up with
+          an earlier stream_ordering than the join.
+        * you get a sync response with a sync token which is _after_ the ban, but before
+          the join
+        * now your join lands; it is a valid event because its `prev_event`s predate the
+          ban, but will not make it into current_state_events (because bans win over
+          joins in state res, essentially).
+        * When we do a sync from the incremental sync, the only event in the timeline
+          is your join ... and yet you aren't joined.
+
+        The ban coming in over federation isn't crucial for this behaviour; the key
+        requirements are:
+        1. the homeserver generates a join event with prev_events that precede the ban
+           (so that it passes the "are you banned" test)
+        2. the join event has a stream_ordering after that of the ban.
+
+        We use monkeypatching to artificially trigger condition (1).
+        """
+        # A local user Alice creates a room.
+        owner = self.register_user("alice", "password")
+        owner_tok = self.login(owner, "password")
+        room_id = self.helper.create_room_as(owner, is_public=True, tok=owner_tok)
+
+        # Do a sync as Alice to get the latest event in the room.
+        alice_sync_result: SyncResult = self.get_success(
+            self.sync_handler.wait_for_sync_for_user(
+                create_requester(owner), generate_sync_config(owner)
+            )
+        )
+        self.assertEqual(len(alice_sync_result.joined), 1)
+        self.assertEqual(alice_sync_result.joined[0].room_id, room_id)
+        last_room_creation_event_id = (
+            alice_sync_result.joined[0].timeline.events[-1].event_id
+        )
+
+        # Eve, a ne'er-do-well, registers.
+        eve = self.register_user("eve", "password")
+        eve_token = self.login(eve, "password")
+
+        # Alice preemptively bans Eve.
+        self.helper.ban(room_id, owner, eve, tok=owner_tok)
+
+        # Eve syncs.
+        eve_requester = create_requester(eve)
+        eve_sync_config = generate_sync_config(eve)
+        eve_sync_after_ban: SyncResult = self.get_success(
+            self.sync_handler.wait_for_sync_for_user(eve_requester, eve_sync_config)
+        )
+
+        # Sanity check this sync result. We shouldn't be joined to the room.
+        self.assertEqual(eve_sync_after_ban.joined, [])
+
+        # Eve tries to join the room. We monkey patch the internal logic which selects
+        # the prev_events used when creating the join event, such that the ban does not
+        # precede the join.
+        mocked_get_prev_events = patch.object(
+            self.hs.get_datastore(),
+            "get_prev_events_for_room",
+            new_callable=MagicMock,
+            return_value=make_awaitable([last_room_creation_event_id]),
+        )
+        with mocked_get_prev_events:
+            self.helper.join(room_id, eve, tok=eve_token)
+
+        # Eve makes a second, incremental sync.
+        eve_incremental_sync_after_join: SyncResult = self.get_success(
+            self.sync_handler.wait_for_sync_for_user(
+                eve_requester,
+                eve_sync_config,
+                since_token=eve_sync_after_ban.next_batch,
+            )
+        )
+        # Eve should not see herself as joined to the room.
+        self.assertEqual(eve_incremental_sync_after_join.joined, [])
+
+        # If we did a third initial sync, we should _still_ see eve is not joined to the room.
+        eve_initial_sync_after_join: SyncResult = self.get_success(
+            self.sync_handler.wait_for_sync_for_user(
+                eve_requester,
+                eve_sync_config,
+                since_token=None,
+            )
+        )
+        self.assertEqual(eve_initial_sync_after_join.joined, [])
+
 
 _request_key = 0
 
diff --git a/tests/http/test_webclient.py b/tests/http/test_webclient.py
new file mode 100644
index 00000000..ee5cf299
--- /dev/null
+++ b/tests/http/test_webclient.py
@@ -0,0 +1,108 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from http import HTTPStatus
+from typing import Dict
+
+from twisted.web.resource import Resource
+
+from synapse.app.homeserver import SynapseHomeServer
+from synapse.config.server import HttpListenerConfig, HttpResourceConfig, ListenerConfig
+from synapse.http.site import SynapseSite
+
+from tests.server import make_request
+from tests.unittest import HomeserverTestCase, create_resource_tree, override_config
+
+
+class WebClientTests(HomeserverTestCase):
+    @override_config(
+        {
+            "web_client_location": "https://example.org",
+        }
+    )
+    def test_webclient_resolves_with_client_resource(self):
+        """
+        Tests that both client and webclient resources can be accessed simultaneously.
+
+        This is a regression test created in response to https://github.com/matrix-org/synapse/issues/11763.
+        """
+        for resource_name_order_list in [
+            ["webclient", "client"],
+            ["client", "webclient"],
+        ]:
+            # Create a dictionary from path regex -> resource
+            resource_dict: Dict[str, Resource] = {}
+
+            for resource_name in resource_name_order_list:
+                resource_dict.update(
+                    SynapseHomeServer._configure_named_resource(self.hs, resource_name)
+                )
+
+            # Create a root resource which ties the above resources together into one
+            root_resource = Resource()
+            create_resource_tree(resource_dict, root_resource)
+
+            # Create a site configured with this resource to make HTTP requests against
+            listener_config = ListenerConfig(
+                port=8008,
+                bind_addresses=["127.0.0.1"],
+                type="http",
+                http_options=HttpListenerConfig(
+                    resources=[HttpResourceConfig(names=resource_name_order_list)]
+                ),
+            )
+            test_site = SynapseSite(
+                logger_name="synapse.access.http.fake",
+                site_tag=self.hs.config.server.server_name,
+                config=listener_config,
+                resource=root_resource,
+                server_version_string="1",
+                max_request_body_size=1234,
+                reactor=self.reactor,
+            )
+
+            # Attempt to make requests to endpoints on both the webclient and client resources
+            # on test_site.
+            self._request_client_and_webclient_resources(test_site)
+
+    def _request_client_and_webclient_resources(self, test_site: SynapseSite) -> None:
+        """Make a request to an endpoint on both the webclient and client-server resources
+        of the given SynapseSite.
+
+        Args:
+            test_site: The SynapseSite object to make requests against.
+        """
+
+        # Ensure that the *webclient* resource is behaving as expected (we get redirected to
+        # the configured web_client_location)
+        channel = make_request(
+            self.reactor,
+            site=test_site,
+            method="GET",
+            path="/_matrix/client",
+        )
+        # Check that we are being redirected to the webclient location URI.
+        self.assertEqual(channel.code, HTTPStatus.FOUND)
+        self.assertEqual(
+            channel.headers.getRawHeaders("Location"), ["https://example.org"]
+        )
+
+        # Ensure that a request to the *client* resource works.
+        channel = make_request(
+            self.reactor,
+            site=test_site,
+            method="GET",
+            path="/_matrix/client/v3/login",
+        )
+        self.assertEqual(channel.code, HTTPStatus.OK)
+        self.assertIn("flows", channel.json_body)
diff --git a/tests/rest/admin/test_federation.py b/tests/rest/admin/test_federation.py
index 742f1942..b70350b6 100644
--- a/tests/rest/admin/test_federation.py
+++ b/tests/rest/admin/test_federation.py
@@ -314,15 +314,12 @@ class FederationTestCase(unittest.HomeserverTestCase):
             retry_interval,
             last_successful_stream_ordering,
         ) in dest:
-            self.get_success(
-                self.store.set_destination_retry_timings(
-                    destination, failure_ts, retry_last_ts, retry_interval
-                )
-            )
-            self.get_success(
-                self.store.set_destination_last_successful_stream_ordering(
-                    destination, last_successful_stream_ordering
-                )
+            self._create_destination(
+                destination,
+                failure_ts,
+                retry_last_ts,
+                retry_interval,
+                last_successful_stream_ordering,
             )
 
         # order by default (destination)
@@ -413,11 +410,9 @@ class FederationTestCase(unittest.HomeserverTestCase):
         _search_test(None, "foo")
         _search_test(None, "bar")
 
-    def test_get_single_destination(self) -> None:
-        """
-        Get one specific destinations.
-        """
-        self._create_destinations(5)
+    def test_get_single_destination_with_retry_timings(self) -> None:
+        """Get one specific destination which has retry timings."""
+        self._create_destinations(1)
 
         channel = self.make_request(
             "GET",
@@ -432,6 +427,53 @@ class FederationTestCase(unittest.HomeserverTestCase):
         # convert channel.json_body into a List
         self._check_fields([channel.json_body])
 
+    def test_get_single_destination_no_retry_timings(self) -> None:
+        """Get one specific destination which has no retry timings."""
+        self._create_destination("sub0.example.com")
+
+        channel = self.make_request(
+            "GET",
+            self.url + "/sub0.example.com",
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
+        self.assertEqual("sub0.example.com", channel.json_body["destination"])
+        self.assertEqual(0, channel.json_body["retry_last_ts"])
+        self.assertEqual(0, channel.json_body["retry_interval"])
+        self.assertIsNone(channel.json_body["failure_ts"])
+        self.assertIsNone(channel.json_body["last_successful_stream_ordering"])
+
+    def _create_destination(
+        self,
+        destination: str,
+        failure_ts: Optional[int] = None,
+        retry_last_ts: int = 0,
+        retry_interval: int = 0,
+        last_successful_stream_ordering: Optional[int] = None,
+    ) -> None:
+        """Create one specific destination
+
+        Args:
+            destination: the destination we have successfully sent to
+            failure_ts: when the server started failing (ms since epoch)
+            retry_last_ts: time of last retry attempt in unix epoch ms
+            retry_interval: how long until next retry in ms
+            last_successful_stream_ordering: the stream_ordering of the most
+                recent successfully-sent PDU
+        """
+        self.get_success(
+            self.store.set_destination_retry_timings(
+                destination, failure_ts, retry_last_ts, retry_interval
+            )
+        )
+        if last_successful_stream_ordering is not None:
+            self.get_success(
+                self.store.set_destination_last_successful_stream_ordering(
+                    destination, last_successful_stream_ordering
+                )
+            )
+
     def _create_destinations(self, number_destinations: int) -> None:
         """Create a number of destinations
 
@@ -440,10 +482,7 @@ class FederationTestCase(unittest.HomeserverTestCase):
         """
         for i in range(0, number_destinations):
             dest = f"sub{i}.example.com"
-            self.get_success(self.store.set_destination_retry_timings(dest, 50, 50, 50))
-            self.get_success(
-                self.store.set_destination_last_successful_stream_ordering(dest, 100)
-            )
+            self._create_destination(dest, 50, 50, 50, 100)
 
     def _check_fields(self, content: List[JsonDict]) -> None:
         """Checks that the expected destination attributes are present in content
diff --git a/tests/rest/admin/test_registration_tokens.py b/tests/rest/admin/test_registration_tokens.py
index 81f3ac7f..8513b1d2 100644
--- a/tests/rest/admin/test_registration_tokens.py
+++ b/tests/rest/admin/test_registration_tokens.py
@@ -223,20 +223,13 @@ class ManageRegistrationTokensTestCase(unittest.HomeserverTestCase):
         # Create all possible single character tokens
         tokens = []
         for c in string.ascii_letters + string.digits + "._~-":
-            tokens.append(
-                {
-                    "token": c,
-                    "uses_allowed": None,
-                    "pending": 0,
-                    "completed": 0,
-                    "expiry_time": None,
-                }
-            )
+            tokens.append((c, None, 0, 0, None))
         self.get_success(
             self.store.db_pool.simple_insert_many(
                 "registration_tokens",
-                tokens,
-                "create_all_registration_tokens",
+                keys=("token", "uses_allowed", "pending", "completed", "expiry_time"),
+                values=tokens,
+                desc="create_all_registration_tokens",
             )
         )
 
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index d2c8781c..3495a036 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -1089,6 +1089,8 @@ class RoomTestCase(unittest.HomeserverTestCase):
             )
             room_ids.append(room_id)
 
+        room_ids.sort()
+
         # Request the list of rooms
         url = "/_synapse/admin/v1/rooms"
         channel = self.make_request(
@@ -1360,6 +1362,12 @@ class RoomTestCase(unittest.HomeserverTestCase):
         room_id_2 = self.helper.create_room_as(self.admin_user, tok=self.admin_user_tok)
         room_id_3 = self.helper.create_room_as(self.admin_user, tok=self.admin_user_tok)
 
+        # Also create a list sorted by IDs for properties that are equal (and thus sorted by room_id)
+        sorted_by_room_id_asc = [room_id_1, room_id_2, room_id_3]
+        sorted_by_room_id_asc.sort()
+        sorted_by_room_id_desc = sorted_by_room_id_asc.copy()
+        sorted_by_room_id_desc.reverse()
+
         # Set room names in alphabetical order. room 1 -> A, 2 -> B, 3 -> C
         self.helper.send_state(
             room_id_1,
@@ -1405,41 +1413,42 @@ class RoomTestCase(unittest.HomeserverTestCase):
         _order_test("canonical_alias", [room_id_1, room_id_2, room_id_3])
         _order_test("canonical_alias", [room_id_3, room_id_2, room_id_1], reverse=True)
 
+        # Note: joined_member counts are sorted in descending order when dir=f
         _order_test("joined_members", [room_id_3, room_id_2, room_id_1])
         _order_test("joined_members", [room_id_1, room_id_2, room_id_3], reverse=True)
 
+        # Note: joined_local_member counts are sorted in descending order when dir=f
         _order_test("joined_local_members", [room_id_3, room_id_2, room_id_1])
         _order_test(
             "joined_local_members", [room_id_1, room_id_2, room_id_3], reverse=True
         )
 
-        _order_test("version", [room_id_1, room_id_2, room_id_3])
-        _order_test("version", [room_id_1, room_id_2, room_id_3], reverse=True)
+        # Note: versions are sorted in descending order when dir=f
+        _order_test("version", sorted_by_room_id_asc, reverse=True)
+        _order_test("version", sorted_by_room_id_desc)
 
-        _order_test("creator", [room_id_1, room_id_2, room_id_3])
-        _order_test("creator", [room_id_1, room_id_2, room_id_3], reverse=True)
+        _order_test("creator", sorted_by_room_id_asc)
+        _order_test("creator", sorted_by_room_id_desc, reverse=True)
 
-        _order_test("encryption", [room_id_1, room_id_2, room_id_3])
-        _order_test("encryption", [room_id_1, room_id_2, room_id_3], reverse=True)
+        _order_test("encryption", sorted_by_room_id_asc)
+        _order_test("encryption", sorted_by_room_id_desc, reverse=True)
 
-        _order_test("federatable", [room_id_1, room_id_2, room_id_3])
-        _order_test("federatable", [room_id_1, room_id_2, room_id_3], reverse=True)
+        _order_test("federatable", sorted_by_room_id_asc)
+        _order_test("federatable", sorted_by_room_id_desc, reverse=True)
 
-        _order_test("public", [room_id_1, room_id_2, room_id_3])
-        # Different sort order of SQlite and PostreSQL
-        # _order_test("public", [room_id_3, room_id_2, room_id_1], reverse=True)
+        _order_test("public", sorted_by_room_id_asc)
+        _order_test("public", sorted_by_room_id_desc, reverse=True)
 
-        _order_test("join_rules", [room_id_1, room_id_2, room_id_3])
-        _order_test("join_rules", [room_id_1, room_id_2, room_id_3], reverse=True)
+        _order_test("join_rules", sorted_by_room_id_asc)
+        _order_test("join_rules", sorted_by_room_id_desc, reverse=True)
 
-        _order_test("guest_access", [room_id_1, room_id_2, room_id_3])
-        _order_test("guest_access", [room_id_1, room_id_2, room_id_3], reverse=True)
+        _order_test("guest_access", sorted_by_room_id_asc)
+        _order_test("guest_access", sorted_by_room_id_desc, reverse=True)
 
-        _order_test("history_visibility", [room_id_1, room_id_2, room_id_3])
-        _order_test(
-            "history_visibility", [room_id_1, room_id_2, room_id_3], reverse=True
-        )
+        _order_test("history_visibility", sorted_by_room_id_asc)
+        _order_test("history_visibility", sorted_by_room_id_desc, reverse=True)
 
+        # Note: state_event counts are sorted in descending order when dir=f
         _order_test("state_events", [room_id_3, room_id_2, room_id_1])
         _order_test("state_events", [room_id_1, room_id_2, room_id_3], reverse=True)
 
diff --git a/tests/rest/admin/test_user.py b/tests/rest/admin/test_user.py
index e0b9fe8e..97114057 100644
--- a/tests/rest/admin/test_user.py
+++ b/tests/rest/admin/test_user.py
@@ -1181,6 +1181,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
                 self.other_user, device_id=None, valid_until_ms=None
             )
         )
+
         self.url_prefix = "/_synapse/admin/v2/users/%s"
         self.url_other_user = self.url_prefix % self.other_user
 
@@ -1188,7 +1189,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         """
         If the user is not a server admin, an error is returned.
         """
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         channel = self.make_request(
             "GET",
@@ -1216,7 +1217,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
 
         channel = self.make_request(
             "GET",
-            "/_synapse/admin/v2/users/@unknown_person:test",
+            self.url_prefix % "@unknown_person:test",
             access_token=self.admin_user_tok,
         )
 
@@ -1337,7 +1338,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         """
         Check that a new admin user is created successfully.
         """
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user (server admin)
         body = {
@@ -1386,7 +1387,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         """
         Check that a new regular user is created successfully.
         """
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user
         body = {
@@ -1478,7 +1479,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         )
 
         # Register new user with admin API
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user
         channel = self.make_request(
@@ -1515,7 +1516,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         )
 
         # Register new user with admin API
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user
         channel = self.make_request(
@@ -1545,7 +1546,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         Check that a new regular user is created successfully and
         got an email pusher.
         """
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user
         body = {
@@ -1588,7 +1589,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         Check that a new regular user is created successfully and
         got not an email pusher.
         """
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user
         body = {
@@ -2085,10 +2086,13 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
         self.assertEqual("@user:test", channel.json_body["name"])
         self.assertTrue(channel.json_body["deactivated"])
-        self.assertIsNone(channel.json_body["password_hash"])
         self.assertEqual(0, len(channel.json_body["threepids"]))
         self.assertEqual("mxc://servername/mediaid", channel.json_body["avatar_url"])
         self.assertEqual("User", channel.json_body["displayname"])
+
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
         # the user is deactivated, the threepid will be deleted
 
         # Get user
@@ -2101,11 +2105,13 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
         self.assertEqual("@user:test", channel.json_body["name"])
         self.assertTrue(channel.json_body["deactivated"])
-        self.assertIsNone(channel.json_body["password_hash"])
         self.assertEqual(0, len(channel.json_body["threepids"]))
         self.assertEqual("mxc://servername/mediaid", channel.json_body["avatar_url"])
         self.assertEqual("User", channel.json_body["displayname"])
 
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
     @override_config({"user_directory": {"enabled": True, "search_all_users": True}})
     def test_change_name_deactivate_user_user_directory(self):
         """
@@ -2177,9 +2183,11 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
         self.assertEqual("@user:test", channel.json_body["name"])
         self.assertFalse(channel.json_body["deactivated"])
-        self.assertIsNotNone(channel.json_body["password_hash"])
         self._is_erased("@user:test", False)
 
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
     @override_config({"password_config": {"localdb_enabled": False}})
     def test_reactivate_user_localdb_disabled(self):
         """
@@ -2209,9 +2217,11 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
         self.assertEqual("@user:test", channel.json_body["name"])
         self.assertFalse(channel.json_body["deactivated"])
-        self.assertIsNone(channel.json_body["password_hash"])
         self._is_erased("@user:test", False)
 
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
     @override_config({"password_config": {"enabled": False}})
     def test_reactivate_user_password_disabled(self):
         """
@@ -2241,9 +2251,11 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
         self.assertEqual("@user:test", channel.json_body["name"])
         self.assertFalse(channel.json_body["deactivated"])
-        self.assertIsNone(channel.json_body["password_hash"])
         self._is_erased("@user:test", False)
 
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
     def test_set_user_as_admin(self):
         """
         Test setting the admin flag on a user.
@@ -2328,7 +2340,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         Ensure an account can't accidentally be deactivated by using a str value
         for the deactivated body parameter
         """
-        url = "/_synapse/admin/v2/users/@bob:test"
+        url = self.url_prefix % "@bob:test"
 
         # Create user
         channel = self.make_request(
@@ -2392,18 +2404,20 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         # Deactivate the user.
         channel = self.make_request(
             "PUT",
-            "/_synapse/admin/v2/users/%s" % urllib.parse.quote(user_id),
+            self.url_prefix % urllib.parse.quote(user_id),
             access_token=self.admin_user_tok,
             content={"deactivated": True},
         )
         self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
         self.assertTrue(channel.json_body["deactivated"])
-        self.assertIsNone(channel.json_body["password_hash"])
         self._is_erased(user_id, False)
         d = self.store.mark_user_erased(user_id)
         self.assertIsNone(self.get_success(d))
         self._is_erased(user_id, True)
 
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
     def _check_fields(self, content: JsonDict):
         """Checks that the expected user attributes are present in content
 
@@ -2416,13 +2430,15 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         self.assertIn("admin", content)
         self.assertIn("deactivated", content)
         self.assertIn("shadow_banned", content)
-        self.assertIn("password_hash", content)
         self.assertIn("creation_ts", content)
         self.assertIn("appservice_id", content)
         self.assertIn("consent_server_notice_sent", content)
         self.assertIn("consent_version", content)
         self.assertIn("external_ids", content)
 
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", content)
+
 
 class UserMembershipRestTestCase(unittest.HomeserverTestCase):
 
diff --git a/tests/rest/client/test_relations.py b/tests/rest/client/test_relations.py
index c026d526..c9b220e7 100644
--- a/tests/rest/client/test_relations.py
+++ b/tests/rest/client/test_relations.py
@@ -21,6 +21,7 @@ from unittest.mock import patch
 from synapse.api.constants import EventTypes, RelationTypes
 from synapse.rest import admin
 from synapse.rest.client import login, register, relations, room, sync
+from synapse.types import JsonDict
 
 from tests import unittest
 from tests.server import FakeChannel
@@ -93,11 +94,6 @@ class RelationsTestCase(unittest.HomeserverTestCase):
             channel.json_body,
         )
 
-    def test_deny_membership(self):
-        """Test that we deny relations on membership events"""
-        channel = self._send_relation(RelationTypes.ANNOTATION, EventTypes.Member)
-        self.assertEquals(400, channel.code, channel.json_body)
-
     def test_deny_invalid_event(self):
         """Test that we deny relations on non-existant events"""
         channel = self._send_relation(
@@ -459,7 +455,14 @@ class RelationsTestCase(unittest.HomeserverTestCase):
 
     @unittest.override_config({"experimental_features": {"msc3440_enabled": True}})
     def test_bundled_aggregations(self):
-        """Test that annotations, references, and threads get correctly bundled."""
+        """
+        Test that annotations, references, and threads get correctly bundled.
+
+        Note that this doesn't test against /relations since only thread relations
+        get bundled via that API. See test_aggregation_get_event_for_thread.
+
+        See test_edit for a similar test for edits.
+        """
         # Setup by sending a variety of relations.
         channel = self._send_relation(RelationTypes.ANNOTATION, "m.reaction", "a")
         self.assertEquals(200, channel.code, channel.json_body)
@@ -487,12 +490,13 @@ class RelationsTestCase(unittest.HomeserverTestCase):
         self.assertEquals(200, channel.code, channel.json_body)
         thread_2 = channel.json_body["event_id"]
 
-        def assert_bundle(actual):
+        def assert_bundle(event_json: JsonDict) -> None:
             """Assert the expected values of the bundled aggregations."""
+            relations_dict = event_json["unsigned"].get("m.relations")
 
             # Ensure the fields are as expected.
             self.assertCountEqual(
-                actual.keys(),
+                relations_dict.keys(),
                 (
                     RelationTypes.ANNOTATION,
                     RelationTypes.REFERENCE,
@@ -508,17 +512,20 @@ class RelationsTestCase(unittest.HomeserverTestCase):
                         {"type": "m.reaction", "key": "b", "count": 1},
                     ]
                 },
-                actual[RelationTypes.ANNOTATION],
+                relations_dict[RelationTypes.ANNOTATION],
             )
 
             self.assertEquals(
                 {"chunk": [{"event_id": reply_1}, {"event_id": reply_2}]},
-                actual[RelationTypes.REFERENCE],
+                relations_dict[RelationTypes.REFERENCE],
             )
 
             self.assertEquals(
                 2,
-                actual[RelationTypes.THREAD].get("count"),
+                relations_dict[RelationTypes.THREAD].get("count"),
+            )
+            self.assertTrue(
+                relations_dict[RelationTypes.THREAD].get("current_user_participated")
             )
             # The latest thread event has some fields that don't matter.
             self.assert_dict(
@@ -535,20 +542,9 @@ class RelationsTestCase(unittest.HomeserverTestCase):
                     "type": "m.room.test",
                     "user_id": self.user_id,
                 },
-                actual[RelationTypes.THREAD].get("latest_event"),
+                relations_dict[RelationTypes.THREAD].get("latest_event"),
             )
 
-        def _find_and_assert_event(events):
-            """
-            Find the parent event in a chunk of events and assert that it has the proper bundled aggregations.
-            """
-            for event in events:
-                if event["event_id"] == self.parent_id:
-                    break
-            else:
-                raise AssertionError(f"Event {self.parent_id} not found in chunk")
-            assert_bundle(event["unsigned"].get("m.relations"))
-
         # Request the event directly.
         channel = self.make_request(
             "GET",
@@ -556,7 +552,7 @@ class RelationsTestCase(unittest.HomeserverTestCase):
             access_token=self.user_token,
         )
         self.assertEquals(200, channel.code, channel.json_body)
-        assert_bundle(channel.json_body["unsigned"].get("m.relations"))
+        assert_bundle(channel.json_body)
 
         # Request the room messages.
         channel = self.make_request(
@@ -565,7 +561,7 @@ class RelationsTestCase(unittest.HomeserverTestCase):
             access_token=self.user_token,
         )
         self.assertEquals(200, channel.code, channel.json_body)
-        _find_and_assert_event(channel.json_body["chunk"])
+        assert_bundle(self._find_event_in_chunk(channel.json_body["chunk"]))
 
         # Request the room context.
         channel = self.make_request(
@@ -574,17 +570,14 @@ class RelationsTestCase(unittest.HomeserverTestCase):
             access_token=self.user_token,
         )
         self.assertEquals(200, channel.code, channel.json_body)
-        assert_bundle(channel.json_body["event"]["unsigned"].get("m.relations"))
+        assert_bundle(channel.json_body["event"])
 
         # Request sync.
-        # channel = self.make_request("GET", "/sync", access_token=self.user_token)
-        # self.assertEquals(200, channel.code, channel.json_body)
-        # room_timeline = channel.json_body["rooms"]["join"][self.room]["timeline"]
-        # self.assertTrue(room_timeline["limited"])
-        # _find_and_assert_event(room_timeline["events"])
-
-        # Note that /relations is tested separately in test_aggregation_get_event_for_thread
-        # since it needs different data configured.
+        channel = self.make_request("GET", "/sync", access_token=self.user_token)
+        self.assertEquals(200, channel.code, channel.json_body)
+        room_timeline = channel.json_body["rooms"]["join"][self.room]["timeline"]
+        self.assertTrue(room_timeline["limited"])
+        self._find_event_in_chunk(room_timeline["events"])
 
     def test_aggregation_get_event_for_annotation(self):
         """Test that annotations do not get bundled aggregations included
@@ -779,25 +772,58 @@ class RelationsTestCase(unittest.HomeserverTestCase):
 
         edit_event_id = channel.json_body["event_id"]
 
+        def assert_bundle(event_json: JsonDict) -> None:
+            """Assert the expected values of the bundled aggregations."""
+            relations_dict = event_json["unsigned"].get("m.relations")
+            self.assertIn(RelationTypes.REPLACE, relations_dict)
+
+            m_replace_dict = relations_dict[RelationTypes.REPLACE]
+            for key in ["event_id", "sender", "origin_server_ts"]:
+                self.assertIn(key, m_replace_dict)
+
+            self.assert_dict(
+                {"event_id": edit_event_id, "sender": self.user_id}, m_replace_dict
+            )
+
         channel = self.make_request(
             "GET",
-            "/rooms/%s/event/%s" % (self.room, self.parent_id),
+            f"/rooms/{self.room}/event/{self.parent_id}",
             access_token=self.user_token,
         )
         self.assertEquals(200, channel.code, channel.json_body)
-
         self.assertEquals(channel.json_body["content"], new_body)
+        assert_bundle(channel.json_body)
 
-        relations_dict = channel.json_body["unsigned"].get("m.relations")
-        self.assertIn(RelationTypes.REPLACE, relations_dict)
+        # Request the room messages.
+        channel = self.make_request(
+            "GET",
+            f"/rooms/{self.room}/messages?dir=b",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        assert_bundle(self._find_event_in_chunk(channel.json_body["chunk"]))
 
-        m_replace_dict = relations_dict[RelationTypes.REPLACE]
-        for key in ["event_id", "sender", "origin_server_ts"]:
-            self.assertIn(key, m_replace_dict)
+        # Request the room context.
+        channel = self.make_request(
+            "GET",
+            f"/rooms/{self.room}/context/{self.parent_id}",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        assert_bundle(channel.json_body["event"])
 
-        self.assert_dict(
-            {"event_id": edit_event_id, "sender": self.user_id}, m_replace_dict
+        # Request sync, but limit the timeline so it becomes limited (and includes
+        # bundled aggregations).
+        filter = urllib.parse.quote_plus(
+            '{"room": {"timeline": {"limit": 2}}}'.encode()
         )
+        channel = self.make_request(
+            "GET", f"/sync?filter={filter}", access_token=self.user_token
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        room_timeline = channel.json_body["rooms"]["join"][self.room]["timeline"]
+        self.assertTrue(room_timeline["limited"])
+        assert_bundle(self._find_event_in_chunk(room_timeline["events"]))
 
     def test_multi_edit(self):
         """Test that multiple edits, including attempts by people who
@@ -1104,6 +1130,16 @@ class RelationsTestCase(unittest.HomeserverTestCase):
         self.assertEquals(200, channel.code, channel.json_body)
         self.assertEquals(channel.json_body["chunk"], [])
 
+    def _find_event_in_chunk(self, events: List[JsonDict]) -> JsonDict:
+        """
+        Find the parent event in a chunk of events and assert that it has the proper bundled aggregations.
+        """
+        for event in events:
+            if event["event_id"] == self.parent_id:
+                return event
+
+        raise AssertionError(f"Event {self.parent_id} not found in chunk")
+
     def _send_relation(
         self,
         relation_type: str,
@@ -1119,7 +1155,8 @@ class RelationsTestCase(unittest.HomeserverTestCase):
             relation_type: One of `RelationTypes`
             event_type: The type of the event to create
             key: The aggregation key used for m.annotation relation type.
-            content: The content of the created event.
+            content: The content of the created event. Will be modified to configure
+                the m.relates_to key based on the other provided parameters.
             access_token: The access token used to send the relation, defaults
                 to `self.user_token`
             parent_id: The event_id this relation relates to. If None, then self.parent_id
@@ -1130,17 +1167,21 @@ class RelationsTestCase(unittest.HomeserverTestCase):
         if not access_token:
             access_token = self.user_token
 
-        query = ""
-        if key:
-            query = "?key=" + urllib.parse.quote_plus(key.encode("utf-8"))
-
         original_id = parent_id if parent_id else self.parent_id
 
+        if content is None:
+            content = {}
+        content["m.relates_to"] = {
+            "event_id": original_id,
+            "rel_type": relation_type,
+        }
+        if key is not None:
+            content["m.relates_to"]["key"] = key
+
         channel = self.make_request(
             "POST",
-            "/_matrix/client/unstable/rooms/%s/send_relation/%s/%s/%s%s"
-            % (self.room, original_id, relation_type, event_type, query),
-            content or {},
+            f"/_matrix/client/v3/rooms/{self.room}/send/{event_type}",
+            content,
             access_token=access_token,
         )
         return channel
diff --git a/tests/rest/client/test_retention.py b/tests/rest/client/test_retention.py
index b5845219..fe5b536d 100644
--- a/tests/rest/client/test_retention.py
+++ b/tests/rest/client/test_retention.py
@@ -228,7 +228,7 @@ class RetentionTestCase(unittest.HomeserverTestCase):
         self.assertIsNotNone(event)
 
         time_now = self.clock.time_msec()
-        serialized = self.get_success(self.serializer.serialize_event(event, time_now))
+        serialized = self.serializer.serialize_event(event, time_now)
 
         return serialized
 
diff --git a/tests/rest/client/utils.py b/tests/rest/client/utils.py
index 1af5e5ce..84243835 100644
--- a/tests/rest/client/utils.py
+++ b/tests/rest/client/utils.py
@@ -196,6 +196,16 @@ class RestHelper:
             expect_code=expect_code,
         )
 
+    def ban(self, room: str, src: str, targ: str, **kwargs: object):
+        """A convenience helper: `change_membership` with `membership` preset to "ban"."""
+        self.change_membership(
+            room=room,
+            src=src,
+            targ=targ,
+            membership=Membership.BAN,
+            **kwargs,
+        )
+
     def change_membership(
         self,
         room: str,
diff --git a/tests/server.py b/tests/server.py
index ca2b7a5b..a0cd14ea 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -14,6 +14,8 @@
 import hashlib
 import json
 import logging
+import os
+import os.path
 import time
 import uuid
 import warnings
@@ -71,6 +73,7 @@ from tests.utils import (
     POSTGRES_HOST,
     POSTGRES_PASSWORD,
     POSTGRES_USER,
+    SQLITE_PERSIST_DB,
     USE_POSTGRES_FOR_TESTS,
     MockClock,
     default_config,
@@ -739,9 +742,23 @@ def setup_test_homeserver(
             },
         }
     else:
+        if SQLITE_PERSIST_DB:
+            # The current working directory is in _trial_temp, so this gets created within that directory.
+            test_db_location = os.path.abspath("test.db")
+            logger.debug("Will persist db to %s", test_db_location)
+            # Ensure each test gets a clean database.
+            try:
+                os.remove(test_db_location)
+            except FileNotFoundError:
+                pass
+            else:
+                logger.debug("Removed existing DB at %s", test_db_location)
+        else:
+            test_db_location = ":memory:"
+
         database_config = {
             "name": "sqlite3",
-            "args": {"database": ":memory:", "cp_min": 1, "cp_max": 1},
+            "args": {"database": test_db_location, "cp_min": 1, "cp_max": 1},
         }
 
     if "db_txn_limit" in kwargs:
diff --git a/tests/storage/test_event_federation.py b/tests/storage/test_event_federation.py
index bf780848..2bc89512 100644
--- a/tests/storage/test_event_federation.py
+++ b/tests/storage/test_event_federation.py
@@ -531,17 +531,25 @@ class EventFederationWorkerStoreTestCase(tests.unittest.HomeserverTestCase):
         self.get_success(
             self.store.db_pool.simple_insert_many(
                 table="federation_inbound_events_staging",
+                keys=(
+                    "origin",
+                    "room_id",
+                    "received_ts",
+                    "event_id",
+                    "event_json",
+                    "internal_metadata",
+                ),
                 values=[
-                    {
-                        "origin": "some_origin",
-                        "room_id": room_id,
-                        "received_ts": 0,
-                        "event_id": f"$fake_event_id_{i + 1}",
-                        "event_json": json_encoder.encode(
+                    (
+                        "some_origin",
+                        room_id,
+                        0,
+                        f"$fake_event_id_{i + 1}",
+                        json_encoder.encode(
                             {"prev_events": [prev_event_format(f"$fake_event_id_{i}")]}
                         ),
-                        "internal_metadata": "{}",
-                    }
+                        "{}",
+                    )
                     for i in range(500)
                 ],
                 desc="test_prune_inbound_federation_queue",
diff --git a/tests/test_federation.py b/tests/test_federation.py
index 3eef1c4c..2b9804ab 100644
--- a/tests/test_federation.py
+++ b/tests/test_federation.py
@@ -17,7 +17,9 @@ from unittest.mock import Mock
 from twisted.internet.defer import succeed
 
 from synapse.api.errors import FederationError
+from synapse.api.room_versions import RoomVersions
 from synapse.events import make_event_from_dict
+from synapse.federation.federation_base import event_from_pdu_json
 from synapse.logging.context import LoggingContext
 from synapse.types import UserID, create_requester
 from synapse.util import Clock
@@ -276,3 +278,73 @@ class MessageAcceptTests(unittest.HomeserverTestCase):
             "ed25519:" + remote_self_signing_key in self_signing_key["keys"].keys(),
         )
         self.assertTrue(remote_self_signing_key in self_signing_key["keys"].values())
+
+
+class StripUnsignedFromEventsTestCase(unittest.TestCase):
+    def test_strip_unauthorized_unsigned_values(self):
+        event1 = {
+            "sender": "@baduser:test.serv",
+            "state_key": "@baduser:test.serv",
+            "event_id": "$event1:test.serv",
+            "depth": 1000,
+            "origin_server_ts": 1,
+            "type": "m.room.member",
+            "origin": "test.servx",
+            "content": {"membership": "join"},
+            "auth_events": [],
+            "unsigned": {"malicious garbage": "hackz", "more warez": "more hackz"},
+        }
+        filtered_event = event_from_pdu_json(event1, RoomVersions.V1)
+        # Make sure unauthorized fields are stripped from unsigned
+        self.assertNotIn("more warez", filtered_event.unsigned)
+
+    def test_strip_event_maintains_allowed_fields(self):
+        event2 = {
+            "sender": "@baduser:test.serv",
+            "state_key": "@baduser:test.serv",
+            "event_id": "$event2:test.serv",
+            "depth": 1000,
+            "origin_server_ts": 1,
+            "type": "m.room.member",
+            "origin": "test.servx",
+            "auth_events": [],
+            "content": {"membership": "join"},
+            "unsigned": {
+                "malicious garbage": "hackz",
+                "more warez": "more hackz",
+                "age": 14,
+                "invite_room_state": [],
+            },
+        }
+
+        filtered_event2 = event_from_pdu_json(event2, RoomVersions.V1)
+        self.assertIn("age", filtered_event2.unsigned)
+        self.assertEqual(14, filtered_event2.unsigned["age"])
+        self.assertNotIn("more warez", filtered_event2.unsigned)
+        # Invite_room_state is allowed in events of type m.room.member
+        self.assertIn("invite_room_state", filtered_event2.unsigned)
+        self.assertEqual([], filtered_event2.unsigned["invite_room_state"])
+
+    def test_strip_event_removes_fields_based_on_event_type(self):
+        event3 = {
+            "sender": "@baduser:test.serv",
+            "state_key": "@baduser:test.serv",
+            "event_id": "$event3:test.serv",
+            "depth": 1000,
+            "origin_server_ts": 1,
+            "type": "m.room.power_levels",
+            "origin": "test.servx",
+            "content": {},
+            "auth_events": [],
+            "unsigned": {
+                "malicious garbage": "hackz",
+                "more warez": "more hackz",
+                "age": 14,
+                "invite_room_state": [],
+            },
+        }
+        filtered_event3 = event_from_pdu_json(event3, RoomVersions.V1)
+        self.assertIn("age", filtered_event3.unsigned)
+        # Invite_room_state field is only permitted in event type m.room.member
+        self.assertNotIn("invite_room_state", filtered_event3.unsigned)
+        self.assertNotIn("more warez", filtered_event3.unsigned)
diff --git a/tests/test_utils/__init__.py b/tests/test_utils/__init__.py
index 15ac2bfe..f05a373a 100644
--- a/tests/test_utils/__init__.py
+++ b/tests/test_utils/__init__.py
@@ -19,7 +19,7 @@ import sys
 import warnings
 from asyncio import Future
 from binascii import unhexlify
-from typing import Any, Awaitable, Callable, TypeVar
+from typing import Awaitable, Callable, TypeVar
 from unittest.mock import Mock
 
 import attr
@@ -46,7 +46,7 @@ def get_awaitable_result(awaitable: Awaitable[TV]) -> TV:
     raise Exception("awaitable has not yet completed")
 
 
-def make_awaitable(result: Any) -> Awaitable[Any]:
+def make_awaitable(result: TV) -> Awaitable[TV]:
     """
     Makes an awaitable, suitable for mocking an `async` function.
     This uses Futures as they can be awaited multiple times so can be returned
diff --git a/tests/utils.py b/tests/utils.py
index 6d013e85..c06fc320 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -42,6 +42,10 @@ POSTGRES_HOST = os.environ.get("SYNAPSE_POSTGRES_HOST", None)
 POSTGRES_PASSWORD = os.environ.get("SYNAPSE_POSTGRES_PASSWORD", None)
 POSTGRES_BASE_DB = "_synapse_unit_tests_base_%s" % (os.getpid(),)
 
+# When debugging a specific test, it's occasionally useful to write the
+# DB to disk and query it with the sqlite CLI.
+SQLITE_PERSIST_DB = os.environ.get("SYNAPSE_TEST_PERSIST_SQLITE_DB") is not None
+
 # the dbname we will connect to in order to create the base database.
 POSTGRES_DBNAME_FOR_INITIAL_CREATE = "postgres"
author	Andrej Shadura <andrewsh@debian.org>	2022-01-25 17:19:30 +0100
committer	Andrej Shadura <andrewsh@debian.org>	2022-01-25 17:19:30 +0100
commit	a3314bc3fb01a561884a7f1cfe8cb8161e582655 (patch)
tree	ad313f9f848e964d9028260931dcf64177c23ec0
parent	0e0f67024b1d67178e063ffd2a86cfb78ab1e08a (diff)
parent	0027c02b907486b437772b1cdecbea14d18597d9 (diff)