231 lines
8.1 KiB
Python
231 lines
8.1 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 inspect import isawaitable
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from typing import TYPE_CHECKING
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import txredisapi
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from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
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from synapse.metrics.background_process_metrics import (
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BackgroundProcessLoggingContext,
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run_as_background_process,
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)
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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 __init__(self, *args, **kwargs):
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super().__init__(*args, **kwargs)
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# a logcontext which we use for processing incoming commands. We declare it as a
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# background process so that the CPU stats get reported to prometheus.
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self._logging_context = BackgroundProcessLoggingContext(
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"replication_command_handler"
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)
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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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with PreserveLoggingContext(self._logging_context):
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self._parse_and_dispatch_message(message)
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def _parse_and_dispatch_message(self, message: str):
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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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self.handle_command(cmd)
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def handle_command(self, cmd: Command) -> None:
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"""Handle a command we have received over the replication stream.
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Delegates to `self.handler.on_<COMMAND>` (which can optionally return an
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Awaitable).
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Args:
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cmd: received command
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"""
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cmd_func = getattr(self.handler, "on_%s" % (cmd.NAME,), None)
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if not cmd_func:
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logger.warning("Unhandled command: %r", cmd)
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return
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res = cmd_func(self, cmd)
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# the handler might be a coroutine: fire it off as a background process
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# if so.
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if isawaitable(res):
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run_as_background_process(
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"replication-" + cmd.get_logcontext_id(), lambda: res
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)
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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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# mark the logging context as finished
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self._logging_context.__exit__(None, None, None)
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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 separate 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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