MatrixSynapse/synapse/replication/tcp/redis.py

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# 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, Generic, Optional, Type, TypeVar, cast
import attr
import txredisapi
from zope.interface import implementer
from twisted.internet.address import IPv4Address, IPv6Address
from twisted.internet.interfaces import IAddress, IConnector
from twisted.python.failure import Failure
from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
from synapse.metrics.background_process_metrics import (
BackgroundProcessLoggingContext,
run_as_background_process,
wrap_as_background_process,
)
from synapse.replication.tcp.commands import (
Command,
ReplicateCommand,
parse_command_from_line,
)
from synapse.replication.tcp.protocol import (
IReplicationConnection,
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__)
T = TypeVar("T")
V = TypeVar("V")
@attr.s
class ConstantProperty(Generic[T, V]):
"""A descriptor that returns the given constant, ignoring attempts to set
it.
"""
constant: V = attr.ib()
def __get__(self, obj: Optional[T], objtype: Optional[Type[T]] = None) -> V:
return self.constant
def __set__(self, obj: Optional[T], value: V):
pass
@implementer(IReplicationConnection)
class RedisSubscriber(txredisapi.SubscriberProtocol):
"""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 IReplicationConnection 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:
synapse_handler: The command handler to handle incoming commands.
synapse_stream_name: The *redis* stream name to subscribe to and publish
from (not anything to do with Synapse replication streams).
synapse_outbound_redis_connection: The connection to redis to use to send
commands.
"""
synapse_handler: "ReplicationCommandHandler"
synapse_stream_name: str
synapse_outbound_redis_connection: 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.
with PreserveLoggingContext():
# thanks to `PreserveLoggingContext()`, the new logcontext is guaranteed to
# capture the sentinel context as its containing context and won't prevent
# GC of / unintentionally reactivate what would be the current context.
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.synapse_stream_name)
await make_deferred_yieldable(self.subscribe(self.synapse_stream_name))
logger.info(
"Successfully subscribed to redis stream, sending REPLICATE command"
)
self.synapse_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.synapse_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.synapse_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.synapse_handler.lost_connection(self)
# mark the logging context as finished by triggering `__exit__()`
with PreserveLoggingContext():
with self._logging_context:
pass
# the sentinel context is now active, which may not be correct.
# PreserveLoggingContext() will restore the correct logging context.
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, bg_start_span=False
)
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.synapse_outbound_redis_connection.publish(
self.synapse_stream_name, encoded_string
)
)
class SynapseRedisFactory(txredisapi.RedisFactory):
"""A subclass of RedisFactory that periodically sends pings to ensure that
we detect dead connections.
"""
# We want to *always* retry connecting, txredisapi will stop if there is a
# failure during certain operations, e.g. during AUTH.
continueTrying = cast(bool, ConstantProperty(True))
def __init__(
self,
hs: "HomeServer",
uuid: str,
dbid: Optional[int],
poolsize: int,
isLazy: bool = False,
handler: Type = txredisapi.ConnectionHandler,
charset: str = "utf-8",
password: Optional[str] = None,
replyTimeout: int = 30,
convertNumbers: Optional[int] = True,
):
super().__init__(
uuid=uuid,
dbid=dbid,
poolsize=poolsize,
isLazy=isLazy,
handler=handler,
charset=charset,
password=password,
replyTimeout=replyTimeout,
convertNumbers=convertNumbers,
)
hs.get_clock().looping_call(self._send_ping, 30 * 1000)
@wrap_as_background_process("redis_ping")
async def _send_ping(self):
for connection in self.pool:
try:
await make_deferred_yieldable(connection.ping())
except Exception:
logger.warning("Failed to send ping to a redis connection")
# ReconnectingClientFactory has some logging (if you enable `self.noisy`), but
# it's rubbish. We add our own here.
def startedConnecting(self, connector: IConnector):
logger.info(
"Connecting to redis server %s", format_address(connector.getDestination())
)
super().startedConnecting(connector)
def clientConnectionFailed(self, connector: IConnector, reason: Failure):
logger.info(
"Connection to redis server %s failed: %s",
format_address(connector.getDestination()),
reason.value,
)
super().clientConnectionFailed(connector, reason)
def clientConnectionLost(self, connector: IConnector, reason: Failure):
logger.info(
"Connection to redis server %s lost: %s",
format_address(connector.getDestination()),
reason.value,
)
super().clientConnectionLost(connector, reason)
def format_address(address: IAddress) -> str:
if isinstance(address, (IPv4Address, IPv6Address)):
return "%s:%i" % (address.host, address.port)
return str(address)
class RedisDirectTcpReplicationClientFactory(SynapseRedisFactory):
"""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
protocol = RedisSubscriber
def __init__(
self, hs: "HomeServer", outbound_redis_connection: txredisapi.RedisProtocol
):
super().__init__(
hs,
uuid="subscriber",
dbid=None,
poolsize=1,
replyTimeout=30,
password=hs.config.redis.redis_password,
)
self.synapse_handler = hs.get_tcp_replication()
self.synapse_stream_name = hs.hostname
self.synapse_outbound_redis_connection = outbound_redis_connection
def buildProtocol(self, addr):
p = super().buildProtocol(addr)
p = cast(RedisSubscriber, p)
# 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.synapse_handler = self.synapse_handler
p.synapse_outbound_redis_connection = self.synapse_outbound_redis_connection
p.synapse_stream_name = self.synapse_stream_name
return p
def lazyConnection(
hs: "HomeServer",
host: str = "localhost",
port: int = 6379,
dbid: Optional[int] = None,
reconnect: bool = True,
password: Optional[str] = None,
replyTimeout: int = 30,
) -> txredisapi.RedisProtocol:
"""Creates a connection to Redis that is lazily set up and reconnects if the
connections is lost.
"""
uuid = "%s:%d" % (host, port)
factory = SynapseRedisFactory(
hs,
uuid=uuid,
dbid=dbid,
poolsize=1,
isLazy=True,
handler=txredisapi.ConnectionHandler,
password=password,
replyTimeout=replyTimeout,
)
factory.continueTrying = reconnect
reactor = hs.get_reactor()
reactor.connectTCP(
host, # type: ignore[arg-type]
port,
factory,
timeout=30,
bindAddress=None,
)
return factory.handler