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8ca79613e6
Proactively send out `POSITION` commands (as if we had just received a `REPLICATE`) when we connect to Redis. This is important as other instances won't notice we've connected to issue a `REPLICATE` command (unlike for direct TCP connections). This is only currently an issue if master process reconnects without restarting (if it restarts then it won't have written anything and so other instances probably won't have missed anything).
216 lines
7.6 KiB
Python
216 lines
7.6 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2020 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from typing import TYPE_CHECKING
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import txredisapi
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from synapse.logging.context import make_deferred_yieldable
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.replication.tcp.commands import (
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Command,
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ReplicateCommand,
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parse_command_from_line,
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)
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from synapse.replication.tcp.protocol import (
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AbstractConnection,
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tcp_inbound_commands_counter,
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tcp_outbound_commands_counter,
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)
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if TYPE_CHECKING:
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from synapse.replication.tcp.handler import ReplicationCommandHandler
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
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"""Connection to redis subscribed to replication stream.
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This class fulfils two functions:
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(a) it implements the twisted Protocol API, where it handles the SUBSCRIBEd redis
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connection, parsing *incoming* messages into replication commands, and passing them
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to `ReplicationCommandHandler`
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(b) it implements the AbstractConnection API, where it sends *outgoing* commands
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onto outbound_redis_connection.
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Due to the vagaries of `txredisapi` we don't want to have a custom
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constructor, so instead we expect the defined attributes below to be set
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immediately after initialisation.
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Attributes:
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handler: The command handler to handle incoming commands.
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stream_name: The *redis* stream name to subscribe to and publish from
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(not anything to do with Synapse replication streams).
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outbound_redis_connection: The connection to redis to use to send
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commands.
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"""
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handler = None # type: ReplicationCommandHandler
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stream_name = None # type: str
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outbound_redis_connection = None # type: txredisapi.RedisProtocol
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def connectionMade(self):
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logger.info("Connected to redis")
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super().connectionMade()
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run_as_background_process("subscribe-replication", self._send_subscribe)
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async def _send_subscribe(self):
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# it's important to make sure that we only send the REPLICATE command once we
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# have successfully subscribed to the stream - otherwise we might miss the
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# POSITION response sent back by the other end.
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logger.info("Sending redis SUBSCRIBE for %s", self.stream_name)
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await make_deferred_yieldable(self.subscribe(self.stream_name))
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logger.info(
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"Successfully subscribed to redis stream, sending REPLICATE command"
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)
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self.handler.new_connection(self)
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await self._async_send_command(ReplicateCommand())
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logger.info("REPLICATE successfully sent")
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# We send out our positions when there is a new connection in case the
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# other side missed updates. We do this for Redis connections as the
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# otherside won't know we've connected and so won't issue a REPLICATE.
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self.handler.send_positions_to_connection(self)
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def messageReceived(self, pattern: str, channel: str, message: str):
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"""Received a message from redis.
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"""
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if message.strip() == "":
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# Ignore blank lines
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return
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try:
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cmd = parse_command_from_line(message)
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except Exception:
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logger.exception(
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"Failed to parse replication line: %r", message,
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)
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return
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# We use "redis" as the name here as we don't have 1:1 connections to
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# remote instances.
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tcp_inbound_commands_counter.labels(cmd.NAME, "redis").inc()
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# Now lets try and call on_<CMD_NAME> function
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run_as_background_process(
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"replication-" + cmd.get_logcontext_id(), self.handle_command, cmd
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)
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async def handle_command(self, cmd: Command):
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"""Handle a command we have received over the replication stream.
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By default delegates to on_<COMMAND>, which should return an awaitable.
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Args:
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cmd: received command
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"""
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handled = False
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# First call any command handlers on this instance. These are for redis
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# specific handling.
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cmd_func = getattr(self, "on_%s" % (cmd.NAME,), None)
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if cmd_func:
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await cmd_func(cmd)
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handled = True
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# Then call out to the handler.
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cmd_func = getattr(self.handler, "on_%s" % (cmd.NAME,), None)
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if cmd_func:
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await cmd_func(self, cmd)
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handled = True
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if not handled:
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logger.warning("Unhandled command: %r", cmd)
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def connectionLost(self, reason):
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logger.info("Lost connection to redis")
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super().connectionLost(reason)
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self.handler.lost_connection(self)
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def send_command(self, cmd: Command):
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"""Send a command if connection has been established.
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Args:
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cmd (Command)
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"""
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run_as_background_process("send-cmd", self._async_send_command, cmd)
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async def _async_send_command(self, cmd: Command):
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"""Encode a replication command and send it over our outbound connection"""
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string = "%s %s" % (cmd.NAME, cmd.to_line())
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if "\n" in string:
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raise Exception("Unexpected newline in command: %r", string)
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encoded_string = string.encode("utf-8")
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# We use "redis" as the name here as we don't have 1:1 connections to
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# remote instances.
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tcp_outbound_commands_counter.labels(cmd.NAME, "redis").inc()
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await make_deferred_yieldable(
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self.outbound_redis_connection.publish(self.stream_name, encoded_string)
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)
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class RedisDirectTcpReplicationClientFactory(txredisapi.SubscriberFactory):
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"""This is a reconnecting factory that connects to redis and immediately
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subscribes to a stream.
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Args:
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hs
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outbound_redis_connection: A connection to redis that will be used to
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send outbound commands (this is seperate to the redis connection
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used to subscribe).
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"""
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maxDelay = 5
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continueTrying = True
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protocol = RedisSubscriber
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def __init__(
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self, hs: "HomeServer", outbound_redis_connection: txredisapi.RedisProtocol
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):
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super().__init__()
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# This sets the password on the RedisFactory base class (as
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# SubscriberFactory constructor doesn't pass it through).
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self.password = hs.config.redis.redis_password
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self.handler = hs.get_tcp_replication()
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self.stream_name = hs.hostname
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self.outbound_redis_connection = outbound_redis_connection
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def buildProtocol(self, addr):
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p = super().buildProtocol(addr) # type: RedisSubscriber
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# We do this here rather than add to the constructor of `RedisSubcriber`
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# as to do so would involve overriding `buildProtocol` entirely, however
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# the base method does some other things than just instantiating the
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# protocol.
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p.handler = self.handler
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p.outbound_redis_connection = self.outbound_redis_connection
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p.stream_name = self.stream_name
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p.password = self.password
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return p
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