# -*- coding: utf-8 -*- # Copyright 2018 New Vector 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 abc import logging import re from six import raise_from from six.moves import urllib from twisted.internet import defer from synapse.api.errors import ( CodeMessageException, HttpResponseException, RequestSendFailed, SynapseError, ) from synapse.util.caches.response_cache import ResponseCache from synapse.util.stringutils import random_string logger = logging.getLogger(__name__) class ReplicationEndpoint(object): """Helper base class for defining new replication HTTP endpoints. This creates an endpoint under `/_synapse/replication/:NAME/:PATH_ARGS..` (with an `/:txn_id` prefix for cached requests.), where NAME is a name, PATH_ARGS are a tuple of parameters to be encoded in the URL. For example, if `NAME` is "send_event" and `PATH_ARGS` is `("event_id",)`, with `CACHE` set to true then this generates an endpoint: /_synapse/replication/send_event/:event_id/:txn_id For POST/PUT requests the payload is serialized to json and sent as the body, while for GET requests the payload is added as query parameters. See `_serialize_payload` for details. Incoming requests are handled by overriding `_handle_request`. Servers must call `register` to register the path with the HTTP server. Requests can be sent by calling the client returned by `make_client`. Attributes: NAME (str): A name for the endpoint, added to the path as well as used in logging and metrics. PATH_ARGS (tuple[str]): A list of parameters to be added to the path. Adding parameters to the path (rather than payload) can make it easier to follow along in the log files. METHOD (str): The method of the HTTP request, defaults to POST. Can be one of POST, PUT or GET. If GET then the payload is sent as query parameters rather than a JSON body. CACHE (bool): Whether server should cache the result of the request/ If true then transparently adds a txn_id to all requests, and `_handle_request` must return a Deferred. RETRY_ON_TIMEOUT(bool): Whether or not to retry the request when a 504 is received. """ __metaclass__ = abc.ABCMeta NAME = abc.abstractproperty() PATH_ARGS = abc.abstractproperty() METHOD = "POST" CACHE = True RETRY_ON_TIMEOUT = True def __init__(self, hs): if self.CACHE: self.response_cache = ResponseCache( hs, "repl." + self.NAME, timeout_ms=30 * 60 * 1000 ) assert self.METHOD in ("PUT", "POST", "GET") @abc.abstractmethod def _serialize_payload(**kwargs): """Static method that is called when creating a request. Concrete implementations should have explicit parameters (rather than kwargs) so that an appropriate exception is raised if the client is called with unexpected parameters. All PATH_ARGS must appear in argument list. Returns: Deferred[dict]|dict: If POST/PUT request then dictionary must be JSON serialisable, otherwise must be appropriate for adding as query args. """ return {} @abc.abstractmethod def _handle_request(self, request, **kwargs): """Handle incoming request. This is called with the request object and PATH_ARGS. Returns: Deferred[dict]: A JSON serialisable dict to be used as response body of request. """ pass @classmethod def make_client(cls, hs): """Create a client that makes requests. Returns a callable that accepts the same parameters as `_serialize_payload`. """ clock = hs.get_clock() host = hs.config.worker_replication_host port = hs.config.worker_replication_http_port client = hs.get_simple_http_client() @defer.inlineCallbacks def send_request(**kwargs): data = yield cls._serialize_payload(**kwargs) url_args = [ urllib.parse.quote(kwargs[name], safe="") for name in cls.PATH_ARGS ] if cls.CACHE: txn_id = random_string(10) url_args.append(txn_id) if cls.METHOD == "POST": request_func = client.post_json_get_json elif cls.METHOD == "PUT": request_func = client.put_json elif cls.METHOD == "GET": request_func = client.get_json else: # We have already asserted in the constructor that a # compatible was picked, but lets be paranoid. raise Exception( "Unknown METHOD on %s replication endpoint" % (cls.NAME,) ) uri = "http://%s:%s/_synapse/replication/%s/%s" % ( host, port, cls.NAME, "/".join(url_args), ) try: # We keep retrying the same request for timeouts. This is so that we # have a good idea that the request has either succeeded or failed on # the master, and so whether we should clean up or not. while True: try: result = yield request_func(uri, data) break except CodeMessageException as e: if e.code != 504 or not cls.RETRY_ON_TIMEOUT: raise logger.warn("%s request timed out", cls.NAME) # If we timed out we probably don't need to worry about backing # off too much, but lets just wait a little anyway. yield clock.sleep(1) except HttpResponseException as e: # We convert to SynapseError as we know that it was a SynapseError # on the master process that we should send to the client. (And # importantly, not stack traces everywhere) raise e.to_synapse_error() except RequestSendFailed as e: raise_from(SynapseError(502, "Failed to talk to master"), e) defer.returnValue(result) return send_request def register(self, http_server): """Called by the server to register this as a handler to the appropriate path. """ url_args = list(self.PATH_ARGS) handler = self._handle_request method = self.METHOD if self.CACHE: handler = self._cached_handler url_args.append("txn_id") args = "/".join("(?P<%s>[^/]+)" % (arg,) for arg in url_args) pattern = re.compile("^/_synapse/replication/%s/%s$" % (self.NAME, args)) http_server.register_paths(method, [pattern], handler, self.__class__.__name__) def _cached_handler(self, request, txn_id, **kwargs): """Called on new incoming requests when caching is enabled. Checks if there is a cached response for the request and returns that, otherwise calls `_handle_request` and caches its response. """ # We just use the txn_id here, but we probably also want to use the # other PATH_ARGS as well. assert self.CACHE return self.response_cache.wrap(txn_id, self._handle_request, request, **kwargs)