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# -*- 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 typing import TYPE_CHECKING
import txredisapi
from synapse.logging.context import make_deferred_yieldable
from synapse.metrics.background_process_metrics import 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 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.
"""
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()
# Now lets try and call on_<CMD_NAME> function
run_as_background_process(
"replication-" + cmd.get_logcontext_id(), self.handle_command, cmd
)
async def handle_command(self, cmd: Command):
"""Handle a command we have received over the replication stream.
By default delegates to on_<COMMAND>, which should return an awaitable.
Args:
cmd: received command
"""
handled = False
# First call any command handlers on this instance. These are for redis
# specific handling.
cmd_func = getattr(self, "on_%s" % (cmd.NAME,), None)
if cmd_func:
await cmd_func(cmd)
handled = True
# Then call out to the handler.
cmd_func = getattr(self.handler, "on_%s" % (cmd.NAME,), None)
if cmd_func:
await cmd_func(self, cmd)
handled = True
if not handled:
logger.warning("Unhandled command: %r", cmd)
def connectionLost(self, reason):
logger.info("Lost connection to redis")
super().connectionLost(reason)
self.handler.lost_connection(self)
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 seperate 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
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