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MatrixSynapse/synapse/replication/tcp/handler.py

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# Copyright 2017 Vector Creations Ltd
# Copyright 2020, 2022 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,
Any,
Awaitable,
Dict,
Iterable,
Iterator,
List,
Optional,
Set,
Tuple,
TypeVar,
Union,
)
from prometheus_client import Counter
from typing_extensions import Deque
from twisted.internet.protocol import ReconnectingClientFactory
from synapse.metrics import LaterGauge
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.replication.tcp.commands import (
ClearUserSyncsCommand,
Command,
FederationAckCommand,
PositionCommand,
RdataCommand,
RemoteServerUpCommand,
ReplicateCommand,
UserIpCommand,
UserSyncCommand,
)
from synapse.replication.tcp.protocol import IReplicationConnection
from synapse.replication.tcp.streams import (
STREAMS_MAP,
AccountDataStream,
BackfillStream,
CachesStream,
EventsStream,
FederationStream,
PresenceFederationStream,
PresenceStream,
ReceiptsStream,
Stream,
ToDeviceStream,
TypingStream,
)
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
# number of updates received for each RDATA stream
inbound_rdata_count = Counter(
"synapse_replication_tcp_protocol_inbound_rdata_count", "", ["stream_name"]
)
user_sync_counter = Counter("synapse_replication_tcp_resource_user_sync", "")
federation_ack_counter = Counter("synapse_replication_tcp_resource_federation_ack", "")
remove_pusher_counter = Counter("synapse_replication_tcp_resource_remove_pusher", "")
user_ip_cache_counter = Counter("synapse_replication_tcp_resource_user_ip_cache", "")
# the type of the entries in _command_queues_by_stream
_StreamCommandQueue = Deque[
Tuple[Union[RdataCommand, PositionCommand], IReplicationConnection]
]
class ReplicationCommandHandler:
"""Handles incoming commands from replication as well as sending commands
back out to connections.
"""
def __init__(self, hs: "HomeServer"):
self._replication_data_handler = hs.get_replication_data_handler()
self._presence_handler = hs.get_presence_handler()
self._store = hs.get_datastores().main
self._notifier = hs.get_notifier()
self._clock = hs.get_clock()
self._instance_id = hs.get_instance_id()
self._instance_name = hs.get_instance_name()
# Additional Redis channel suffixes to subscribe to.
self._channels_to_subscribe_to: List[str] = []
self._is_presence_writer = (
hs.get_instance_name() in hs.config.worker.writers.presence
)
self._streams: Dict[str, Stream] = {
stream.NAME: stream(hs) for stream in STREAMS_MAP.values()
}
# List of streams that this instance is the source of
self._streams_to_replicate: List[Stream] = []
for stream in self._streams.values():
if hs.config.redis.redis_enabled and stream.NAME == CachesStream.NAME:
# All workers can write to the cache invalidation stream when
# using redis.
self._streams_to_replicate.append(stream)
continue
if isinstance(stream, (EventsStream, BackfillStream)):
# Only add EventStream and BackfillStream as a source on the
# instance in charge of event persistence.
if hs.get_instance_name() in hs.config.worker.writers.events:
self._streams_to_replicate.append(stream)
continue
if isinstance(stream, ToDeviceStream):
# Only add ToDeviceStream as a source on instances in charge of
# sending to device messages.
if hs.get_instance_name() in hs.config.worker.writers.to_device:
self._streams_to_replicate.append(stream)
continue
if isinstance(stream, TypingStream):
# Only add TypingStream as a source on the instance in charge of
# typing.
if hs.get_instance_name() in hs.config.worker.writers.typing:
self._streams_to_replicate.append(stream)
continue
if isinstance(stream, AccountDataStream):
# Only add AccountDataStream and TagAccountDataStream as a source on the
# instance in charge of account_data persistence.
if hs.get_instance_name() in hs.config.worker.writers.account_data:
self._streams_to_replicate.append(stream)
continue
if isinstance(stream, ReceiptsStream):
# Only add ReceiptsStream as a source on the instance in charge of
# receipts.
if hs.get_instance_name() in hs.config.worker.writers.receipts:
self._streams_to_replicate.append(stream)
continue
if isinstance(stream, (PresenceStream, PresenceFederationStream)):
# Only add PresenceStream as a source on the instance in charge
# of presence.
if self._is_presence_writer:
self._streams_to_replicate.append(stream)
continue
# Only add any other streams if we're on master.
if hs.config.worker.worker_app is not None:
continue
if (
stream.NAME == FederationStream.NAME
and hs.config.worker.send_federation
):
# We only support federation stream if federation sending
# has been disabled on the master.
continue
self._streams_to_replicate.append(stream)
# Map of stream name to batched updates. See RdataCommand for info on
# how batching works.
self._pending_batches: Dict[str, List[Any]] = {}
# The factory used to create connections.
self._factory: Optional[ReconnectingClientFactory] = None
# The currently connected connections. (The list of places we need to send
# outgoing replication commands to.)
self._connections: List[IReplicationConnection] = []
LaterGauge(
"synapse_replication_tcp_resource_total_connections",
"",
[],
lambda: len(self._connections),
)
# When POSITION or RDATA commands arrive, we stick them in a queue and process
# them in order in a separate background process.
# the streams which are currently being processed by _unsafe_process_queue
self._processing_streams: Set[str] = set()
# for each stream, a queue of commands that are awaiting processing, and the
# connection that they arrived on.
self._command_queues_by_stream = {
stream_name: _StreamCommandQueue() for stream_name in self._streams
}
# For each connection, the incoming stream names that have received a POSITION
# from that connection.
self._streams_by_connection: Dict[IReplicationConnection, Set[str]] = {}
LaterGauge(
"synapse_replication_tcp_command_queue",
"Number of inbound RDATA/POSITION commands queued for processing",
["stream_name"],
lambda: {
(stream_name,): len(queue)
for stream_name, queue in self._command_queues_by_stream.items()
},
)
self._is_master = hs.config.worker.worker_app is None
self._federation_sender = None
if self._is_master and not hs.config.worker.send_federation:
self._federation_sender = hs.get_federation_sender()
self._server_notices_sender = None
if self._is_master:
self._server_notices_sender = hs.get_server_notices_sender()
if hs.config.redis.redis_enabled:
# If we're using Redis, it's the background worker that should
# receive USER_IP commands and store the relevant client IPs.
self._should_insert_client_ips = hs.config.worker.run_background_tasks
else:
# If we're NOT using Redis, this must be handled by the master
self._should_insert_client_ips = hs.get_instance_name() == "master"
if self._is_master or self._should_insert_client_ips:
self.subscribe_to_channel("USER_IP")
def subscribe_to_channel(self, channel_name: str) -> None:
"""
Indicates that we wish to subscribe to a Redis channel by name.
(The name will later be prefixed with the server name; i.e. subscribing
to the 'ABC' channel actually subscribes to 'example.com/ABC' Redis-side.)
Raises:
- If replication has already started, then it's too late to subscribe
to new channels.
"""
if self._factory is not None:
# We don't allow subscribing after the fact to avoid the chance
# of missing an important message because we didn't subscribe in time.
raise RuntimeError(
"Cannot subscribe to more channels after replication started."
)
if channel_name not in self._channels_to_subscribe_to:
self._channels_to_subscribe_to.append(channel_name)
def _add_command_to_stream_queue(
self, conn: IReplicationConnection, cmd: Union[RdataCommand, PositionCommand]
) -> None:
"""Queue the given received command for processing
Adds the given command to the per-stream queue, and processes the queue if
necessary
"""
stream_name = cmd.stream_name
queue = self._command_queues_by_stream.get(stream_name)
if queue is None:
logger.error("Got %s for unknown stream: %s", cmd.NAME, stream_name)
return
queue.append((cmd, conn))
# if we're already processing this stream, there's nothing more to do:
# the new entry on the queue will get picked up in due course
if stream_name in self._processing_streams:
return
# fire off a background process to start processing the queue.
run_as_background_process(
"process-replication-data", self._unsafe_process_queue, stream_name
)
async def _unsafe_process_queue(self, stream_name: str) -> None:
"""Processes the command queue for the given stream, until it is empty
Does not check if there is already a thread processing the queue, hence "unsafe"
"""
assert stream_name not in self._processing_streams
self._processing_streams.add(stream_name)
try:
queue = self._command_queues_by_stream.get(stream_name)
while queue:
cmd, conn = queue.popleft()
try:
await self._process_command(cmd, conn, stream_name)
except Exception:
logger.exception("Failed to handle command %s", cmd)
finally:
self._processing_streams.discard(stream_name)
async def _process_command(
self,
cmd: Union[PositionCommand, RdataCommand],
conn: IReplicationConnection,
stream_name: str,
) -> None:
if isinstance(cmd, PositionCommand):
await self._process_position(stream_name, conn, cmd)
elif isinstance(cmd, RdataCommand):
await self._process_rdata(stream_name, conn, cmd)
else:
# This shouldn't be possible
raise Exception("Unrecognised command %s in stream queue", cmd.NAME)
def start_replication(self, hs: "HomeServer") -> None:
"""Helper method to start replication."""
from synapse.replication.tcp.redis import RedisDirectTcpReplicationClientFactory
# First let's ensure that we have a ReplicationStreamer started.
hs.get_replication_streamer()
# We need two connections to redis, one for the subscription stream and
# one to send commands to (as you can't send further redis commands to a
# connection after SUBSCRIBE is called).
# First create the connection for sending commands.
outbound_redis_connection = hs.get_outbound_redis_connection()
# Now create the factory/connection for the subscription stream.
self._factory = RedisDirectTcpReplicationClientFactory(
hs,
outbound_redis_connection,
channel_names=self._channels_to_subscribe_to,
)
hs.get_reactor().connectTCP(
hs.config.redis.redis_host,
hs.config.redis.redis_port,
self._factory,
timeout=30,
bindAddress=None,
)
def get_streams(self) -> Dict[str, Stream]:
"""Get a map from stream name to all streams."""
return self._streams
def get_streams_to_replicate(self) -> List[Stream]:
"""Get a list of streams that this instances replicates."""
return self._streams_to_replicate
def on_REPLICATE(self, conn: IReplicationConnection, cmd: ReplicateCommand) -> None:
self.send_positions_to_connection(conn)
def send_positions_to_connection(self, conn: IReplicationConnection) -> None:
"""Send current position of all streams this process is source of to
the connection.
"""
# We respond with current position of all streams this instance
# replicates.
for stream in self.get_streams_to_replicate():
# Note that we use the current token as the prev token here (rather
# than stream.last_token), as we can't be sure that there have been
# no rows written between last token and the current token (since we
# might be racing with the replication sending bg process).
current_token = stream.current_token(self._instance_name)
self.send_command(
PositionCommand(
stream.NAME,
self._instance_name,
current_token,
current_token,
)
)
def on_USER_SYNC(
self, conn: IReplicationConnection, cmd: UserSyncCommand
) -> Optional[Awaitable[None]]:
user_sync_counter.inc()
if self._is_presence_writer:
return self._presence_handler.update_external_syncs_row(
cmd.instance_id, cmd.user_id, cmd.is_syncing, cmd.last_sync_ms
)
else:
return None
def on_CLEAR_USER_SYNC(
self, conn: IReplicationConnection, cmd: ClearUserSyncsCommand
) -> Optional[Awaitable[None]]:
if self._is_presence_writer:
return self._presence_handler.update_external_syncs_clear(cmd.instance_id)
else:
return None
def on_FEDERATION_ACK(
self, conn: IReplicationConnection, cmd: FederationAckCommand
) -> None:
federation_ack_counter.inc()
if self._federation_sender:
self._federation_sender.federation_ack(cmd.instance_name, cmd.token)
def on_USER_IP(
self, conn: IReplicationConnection, cmd: UserIpCommand
) -> Optional[Awaitable[None]]:
user_ip_cache_counter.inc()
if self._is_master or self._should_insert_client_ips:
# We make a point of only returning an awaitable if there's actually
# something to do; on_USER_IP is not an async function, but
# _handle_user_ip is.
# If on_USER_IP returns an awaitable, it gets scheduled as a
# background process (see `BaseReplicationStreamProtocol.handle_command`).
return self._handle_user_ip(cmd)
else:
# Returning None when this process definitely has nothing to do
# reduces the overhead of handling the USER_IP command, which is
# currently broadcast to all workers regardless of utility.
return None
async def _handle_user_ip(self, cmd: UserIpCommand) -> None:
"""
Handles a User IP, branching depending on whether we are the main process
and/or the background worker.
"""
if self._is_master:
assert self._server_notices_sender is not None
await self._server_notices_sender.on_user_ip(cmd.user_id)
if self._should_insert_client_ips:
await self._store.insert_client_ip(
cmd.user_id,
cmd.access_token,
cmd.ip,
cmd.user_agent,
cmd.device_id,
cmd.last_seen,
)
def on_RDATA(self, conn: IReplicationConnection, cmd: RdataCommand) -> None:
if cmd.instance_name == self._instance_name:
# Ignore RDATA that are just our own echoes
return
stream_name = cmd.stream_name
inbound_rdata_count.labels(stream_name).inc()
# We put the received command into a queue here for two reasons:
# 1. so we don't try and concurrently handle multiple rows for the
# same stream, and
# 2. so we don't race with getting a POSITION command and fetching
# missing RDATA.
self._add_command_to_stream_queue(conn, cmd)
async def _process_rdata(
self, stream_name: str, conn: IReplicationConnection, cmd: RdataCommand
) -> None:
"""Process an RDATA command
Called after the command has been popped off the queue of inbound commands
"""
try:
row = STREAMS_MAP[stream_name].parse_row(cmd.row)
except Exception as e:
raise Exception(
"Failed to parse RDATA: %r %r" % (stream_name, cmd.row)
) from e
# make sure that we've processed a POSITION for this stream *on this
# connection*. (A POSITION on another connection is no good, as there
# is no guarantee that we have seen all the intermediate updates.)
sbc = self._streams_by_connection.get(conn)
if not sbc or stream_name not in sbc:
# Let's drop the row for now, on the assumption we'll receive a
# `POSITION` soon and we'll catch up correctly then.
logger.debug(
"Discarding RDATA for unconnected stream %s -> %s",
stream_name,
cmd.token,
)
return
if cmd.token is None:
# I.e. this is part of a batch of updates for this stream (in
# which case batch until we get an update for the stream with a non
# None token).
self._pending_batches.setdefault(stream_name, []).append(row)
return
# Check if this is the last of a batch of updates
rows = self._pending_batches.pop(stream_name, [])
rows.append(row)
stream = self._streams[stream_name]
# Find where we previously streamed up to.
current_token = stream.current_token(cmd.instance_name)
# Discard this data if this token is earlier than the current
# position. Note that streams can be reset (in which case you
# expect an earlier token), but that must be preceded by a
# POSITION command.
if cmd.token <= current_token:
logger.debug(
"Discarding RDATA from stream %s at position %s before previous position %s",
stream_name,
cmd.token,
current_token,
)
else:
await self.on_rdata(stream_name, cmd.instance_name, cmd.token, rows)
async def on_rdata(
self, stream_name: str, instance_name: str, token: int, rows: list
) -> None:
"""Called to handle a batch of replication data with a given stream token.
Args:
stream_name: name of the replication stream for this batch of rows
instance_name: the instance that wrote the rows.
token: stream token for this batch of rows
rows: a list of Stream.ROW_TYPE objects as returned by
Stream.parse_row.
"""
logger.debug("Received rdata %s (%s) -> %s", stream_name, instance_name, token)
await self._replication_data_handler.on_rdata(
stream_name, instance_name, token, rows
)
def on_POSITION(self, conn: IReplicationConnection, cmd: PositionCommand) -> None:
if cmd.instance_name == self._instance_name:
# Ignore POSITION that are just our own echoes
return
logger.debug("Handling '%s %s'", cmd.NAME, cmd.to_line())
self._add_command_to_stream_queue(conn, cmd)
async def _process_position(
self, stream_name: str, conn: IReplicationConnection, cmd: PositionCommand
) -> None:
"""Process a POSITION command
Called after the command has been popped off the queue of inbound commands
"""
stream = self._streams[stream_name]
# We're about to go and catch up with the stream, so remove from set
# of connected streams.
for streams in self._streams_by_connection.values():
streams.discard(stream_name)
# We clear the pending batches for the stream as the fetching of the
# missing updates below will fetch all rows in the batch.
self._pending_batches.pop(stream_name, [])
# Find where we previously streamed up to.
current_token = stream.current_token(cmd.instance_name)
# If the position token matches our current token then we're up to
# date and there's nothing to do. Otherwise, fetch all updates
# between then and now.
missing_updates = cmd.prev_token != current_token
while missing_updates:
# Note: There may very well not be any new updates, but we check to
# make sure. This can particularly happen for the event stream where
# event persisters continuously send `POSITION`. See `resource.py`
# for why this can happen.
logger.info(
"Fetching replication rows for '%s' between %i and %i",
stream_name,
current_token,
cmd.new_token,
)
(updates, current_token, missing_updates) = await stream.get_updates_since(
cmd.instance_name, current_token, cmd.new_token
)
# TODO: add some tests for this
# Some streams return multiple rows with the same stream IDs,
# which need to be processed in batches.
for token, rows in _batch_updates(updates):
await self.on_rdata(
stream_name,
cmd.instance_name,
token,
[stream.parse_row(row) for row in rows],
)
logger.info("Caught up with stream '%s' to %i", stream_name, cmd.new_token)
# We've now caught up to position sent to us, notify handler.
await self._replication_data_handler.on_position(
cmd.stream_name, cmd.instance_name, cmd.new_token
)
self._streams_by_connection.setdefault(conn, set()).add(stream_name)
def on_REMOTE_SERVER_UP(
self, conn: IReplicationConnection, cmd: RemoteServerUpCommand
) -> None:
"""Called when get a new REMOTE_SERVER_UP command."""
self._replication_data_handler.on_remote_server_up(cmd.data)
self._notifier.notify_remote_server_up(cmd.data)
# We relay to all other connections to ensure every instance gets the
# notification.
#
# When configured to use redis we'll always only have one connection and
# so this is a no-op (all instances will have already received the same
# REMOTE_SERVER_UP command).
#
# For direct TCP connections this will relay to all other connections
# connected to us. When on master this will correctly fan out to all
# other direct TCP clients and on workers there'll only be the one
# connection to master.
#
# (The logic here should also be sound if we have a mix of Redis and
# direct TCP connections so long as there is only one traffic route
# between two instances, but that is not currently supported).
self.send_command(cmd, ignore_conn=conn)
def new_connection(self, connection: IReplicationConnection) -> None:
"""Called when we have a new connection."""
self._connections.append(connection)
# If we are connected to replication as a client (rather than a server)
# we need to reset the reconnection delay on the client factory (which
# is used to do exponential back off when the connection drops).
#
# Ideally we would reset the delay when we've "fully established" the
# connection (for some definition thereof) to stop us from tightlooping
# on reconnection if something fails after this point and we drop the
# connection. Unfortunately, we don't really have a better definition of
# "fully established" than the connection being established.
if self._factory:
self._factory.resetDelay()
# Tell the other end if we have any users currently syncing.
currently_syncing = (
self._presence_handler.get_currently_syncing_users_for_replication()
)
now = self._clock.time_msec()
for user_id in currently_syncing:
connection.send_command(
UserSyncCommand(self._instance_id, user_id, True, now)
)
def lost_connection(self, connection: IReplicationConnection) -> None:
"""Called when a connection is closed/lost."""
# we no longer need _streams_by_connection for this connection.
streams = self._streams_by_connection.pop(connection, None)
if streams:
logger.info(
"Lost replication connection; streams now disconnected: %s", streams
)
try:
self._connections.remove(connection)
except ValueError:
pass
def connected(self) -> bool:
"""Do we have any replication connections open?
Is used by e.g. `ReplicationStreamer` to no-op if nothing is connected.
"""
return bool(self._connections)
def send_command(
self, cmd: Command, ignore_conn: Optional[IReplicationConnection] = None
) -> None:
"""Send a command to all connected connections.
Args:
cmd
ignore_conn: If set don't send command to the given connection.
Used when relaying commands from one connection to all others.
"""
if self._connections:
for connection in self._connections:
if connection == ignore_conn:
continue
try:
connection.send_command(cmd)
except Exception:
# We probably want to catch some types of exceptions here
# and log them as warnings (e.g. connection gone), but I
# can't find what those exception types they would be.
logger.exception(
"Failed to write command %s to connection %s",
cmd.NAME,
connection,
)
else:
logger.warning("Dropping command as not connected: %r", cmd.NAME)
def send_federation_ack(self, token: int) -> None:
"""Ack data for the federation stream. This allows the master to drop
data stored purely in memory.
"""
self.send_command(FederationAckCommand(self._instance_name, token))
def send_user_sync(
self, instance_id: str, user_id: str, is_syncing: bool, last_sync_ms: int
) -> None:
"""Poke the master that a user has started/stopped syncing."""
self.send_command(
UserSyncCommand(instance_id, user_id, is_syncing, last_sync_ms)
)
def send_user_ip(
self,
user_id: str,
access_token: str,
ip: str,
user_agent: str,
device_id: Optional[str],
last_seen: int,
) -> None:
"""Tell the master that the user made a request."""
cmd = UserIpCommand(user_id, access_token, ip, user_agent, device_id, last_seen)
self.send_command(cmd)
def send_remote_server_up(self, server: str) -> None:
self.send_command(RemoteServerUpCommand(server))
def stream_update(self, stream_name: str, token: Optional[int], data: Any) -> None:
"""Called when a new update is available to stream to Redis subscribers.
We need to check if the client is interested in the stream or not
"""
self.send_command(RdataCommand(stream_name, self._instance_name, token, data))
UpdateToken = TypeVar("UpdateToken")
UpdateRow = TypeVar("UpdateRow")
def _batch_updates(
updates: Iterable[Tuple[UpdateToken, UpdateRow]]
) -> Iterator[Tuple[UpdateToken, List[UpdateRow]]]:
"""Collect stream updates with the same token together
Given a series of updates returned by Stream.get_updates_since(), collects
the updates which share the same stream_id together.
For example:
[(1, a), (1, b), (2, c), (3, d), (3, e)]
becomes:
[
(1, [a, b]),
(2, [c]),
(3, [d, e]),
]
"""
update_iter = iter(updates)
first_update = next(update_iter, None)
if first_update is None:
# empty input
return
current_batch_token = first_update[0]
current_batch = [first_update[1]]
for token, row in update_iter:
if token != current_batch_token:
# different token to the previous row: flush the previous
# batch and start anew
yield current_batch_token, current_batch
current_batch_token = token
current_batch = []
current_batch.append(row)
# flush the final batch
yield current_batch_token, current_batch
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