1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
|
# -*- coding: utf-8 -*-
# Copyright 2020 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 logging
from inspect import isawaitable
from typing import TYPE_CHECKING
import txredisapi
from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
from synapse.metrics.background_process_metrics import (
BackgroundProcessLoggingContext,
run_as_background_process,
)
from synapse.replication.tcp.commands import (
Command,
ReplicateCommand,
parse_command_from_line,
)
from synapse.replication.tcp.protocol import (
AbstractConnection,
tcp_inbound_commands_counter,
tcp_outbound_commands_counter,
)
if TYPE_CHECKING:
from synapse.replication.tcp.handler import ReplicationCommandHandler
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
"""Connection to redis subscribed to replication stream.
This class fulfils two functions:
(a) it implements the twisted Protocol API, where it handles the SUBSCRIBEd redis
connection, parsing *incoming* messages into replication commands, and passing them
to `ReplicationCommandHandler`
(b) it implements the AbstractConnection API, where it sends *outgoing* commands
onto outbound_redis_connection.
Due to the vagaries of `txredisapi` we don't want to have a custom
constructor, so instead we expect the defined attributes below to be set
immediately after initialisation.
Attributes:
handler: The command handler to handle incoming commands.
stream_name: The *redis* stream name to subscribe to and publish from
(not anything to do with Synapse replication streams).
outbound_redis_connection: The connection to redis to use to send
commands.
"""
handler = None # type: ReplicationCommandHandler
stream_name = None # type: str
outbound_redis_connection = None # type: txredisapi.RedisProtocol
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
# a logcontext which we use for processing incoming commands. We declare it as a
# background process so that the CPU stats get reported to prometheus.
self._logging_context = BackgroundProcessLoggingContext(
"replication_command_handler"
)
def connectionMade(self):
logger.info("Connected to redis")
super().connectionMade()
run_as_background_process("subscribe-replication", self._send_subscribe)
async def _send_subscribe(self):
# it's important to make sure that we only send the REPLICATE command once we
# have successfully subscribed to the stream - otherwise we might miss the
# POSITION response sent back by the other end.
logger.info("Sending redis SUBSCRIBE for %s", self.stream_name)
await make_deferred_yieldable(self.subscribe(self.stream_name))
logger.info(
"Successfully subscribed to redis stream, sending REPLICATE command"
)
self.handler.new_connection(self)
await self._async_send_command(ReplicateCommand())
logger.info("REPLICATE successfully sent")
# We send out our positions when there is a new connection in case the
# other side missed updates. We do this for Redis connections as the
# otherside won't know we've connected and so won't issue a REPLICATE.
self.handler.send_positions_to_connection(self)
def messageReceived(self, pattern: str, channel: str, message: str):
"""Received a message from redis.
"""
with PreserveLoggingContext(self._logging_context):
self._parse_and_dispatch_message(message)
def _parse_and_dispatch_message(self, message: str):
if message.strip() == "":
# Ignore blank lines
return
try:
cmd = parse_command_from_line(message)
except Exception:
logger.exception(
"Failed to parse replication line: %r", message,
)
return
# We use "redis" as the name here as we don't have 1:1 connections to
# remote instances.
tcp_inbound_commands_counter.labels(cmd.NAME, "redis").inc()
self.handle_command(cmd)
def handle_command(self, cmd: Command) -> None:
"""Handle a command we have received over the replication stream.
Delegates to `self.handler.on_<COMMAND>` (which can optionally return an
Awaitable).
Args:
cmd: received command
"""
cmd_func = getattr(self.handler, "on_%s" % (cmd.NAME,), None)
if not cmd_func:
logger.warning("Unhandled command: %r", cmd)
return
res = cmd_func(self, cmd)
# the handler might be a coroutine: fire it off as a background process
# if so.
if isawaitable(res):
run_as_background_process(
"replication-" + cmd.get_logcontext_id(), lambda: res
)
def connectionLost(self, reason):
logger.info("Lost connection to redis")
super().connectionLost(reason)
self.handler.lost_connection(self)
# mark the logging context as finished
self._logging_context.__exit__(None, None, None)
def send_command(self, cmd: Command):
"""Send a command if connection has been established.
Args:
cmd (Command)
"""
run_as_background_process("send-cmd", self._async_send_command, cmd)
async def _async_send_command(self, cmd: Command):
"""Encode a replication command and send it over our outbound connection"""
string = "%s %s" % (cmd.NAME, cmd.to_line())
if "\n" in string:
raise Exception("Unexpected newline in command: %r", string)
encoded_string = string.encode("utf-8")
# We use "redis" as the name here as we don't have 1:1 connections to
# remote instances.
tcp_outbound_commands_counter.labels(cmd.NAME, "redis").inc()
await make_deferred_yieldable(
self.outbound_redis_connection.publish(self.stream_name, encoded_string)
)
class RedisDirectTcpReplicationClientFactory(txredisapi.SubscriberFactory):
"""This is a reconnecting factory that connects to redis and immediately
subscribes to a stream.
Args:
hs
outbound_redis_connection: A connection to redis that will be used to
send outbound commands (this is separate to the redis connection
used to subscribe).
"""
maxDelay = 5
continueTrying = True
protocol = RedisSubscriber
def __init__(
self, hs: "HomeServer", outbound_redis_connection: txredisapi.RedisProtocol
):
super().__init__()
# This sets the password on the RedisFactory base class (as
# SubscriberFactory constructor doesn't pass it through).
self.password = hs.config.redis.redis_password
self.handler = hs.get_tcp_replication()
self.stream_name = hs.hostname
self.outbound_redis_connection = outbound_redis_connection
def buildProtocol(self, addr):
p = super().buildProtocol(addr) # type: RedisSubscriber
# We do this here rather than add to the constructor of `RedisSubcriber`
# as to do so would involve overriding `buildProtocol` entirely, however
# the base method does some other things than just instantiating the
# protocol.
p.handler = self.handler
p.outbound_redis_connection = self.outbound_redis_connection
p.stream_name = self.stream_name
p.password = self.password
return p
|
