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Wait for a POSITION on the right connection before accepting RDATA

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... otherwise we can believe we're up to date when we're not.
This commit is contained in:
Richard van der Hoff 2020-05-05 19:32:35 +01:00
parent d78265af0c
commit 7f7eedbebb
2 changed files with 39 additions and 20 deletions
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57
synapse/replication/tcp/handler.py
View File

@ -81,9 +81,6 @@ class ReplicationCommandHandler:
self._instance_id = hs.get_instance_id()
self._instance_name = hs.get_instance_name()
# Set of streams that we've caught up with.
self._streams_connected = set() # type: Set[str]
self._streams = {
stream.NAME: stream(hs) for stream in STREAMS_MAP.values()
} # type: Dict[str, Stream]
@ -103,6 +100,9 @@ class ReplicationCommandHandler:
# outgoing replication commands to.)
self._connections = [] # type: List[AbstractConnection]
# For each connection, the incoming streams that are coming from that connection
self._streams_by_connection = {} # type: Dict[AbstractConnection, Set[str]]
LaterGauge(
"synapse_replication_tcp_resource_total_connections",
"",
@ -258,12 +258,14 @@ class ReplicationCommandHandler:
# 2. so we don't race with getting a POSITION command and fetching
# missing RDATA.
with await self._position_linearizer.queue(cmd.stream_name):
if stream_name not in self._streams_connected:
# If the stream isn't marked as connected then we haven't seen a
# `POSITION` command yet, and so we may have missed some rows.
# 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.warning(
logger.info(
"Discarding RDATA for unconnected stream %s -> %s",
stream_name,
cmd.token,
@ -298,30 +300,33 @@ class ReplicationCommandHandler:
# Ignore POSITION that are just our own echoes
return
stream = self._streams.get(cmd.stream_name)
logger.info("Handling '%s %s'", cmd.NAME, cmd.to_line())
stream_name = cmd.stream_name
stream = self._streams.get(stream_name)
if not stream:
logger.error("Got POSITION for unknown stream: %s", cmd.stream_name)
logger.error("Got POSITION for unknown stream: %s", stream_name)
return
# We protect catching up with a linearizer in case the replication
# connection reconnects under us.
with await self._position_linearizer.queue(cmd.stream_name):
with await self._position_linearizer.queue(stream_name):
# We're about to go and catch up with the stream, so remove from set
# of connected streams.
self._streams_connected.discard(cmd.stream_name)
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(cmd.stream_name, [])
self._pending_batches.pop(stream_name, [])
# Find where we previously streamed up to.
current_token = self._replication_data_handler.get_streams_to_replicate().get(
cmd.stream_name
stream_name
)
if current_token is None:
logger.warning(
"Got POSITION for stream we're not subscribed to: %s",
cmd.stream_name,
"Got POSITION for stream we're not subscribed to: %s", stream_name,
)
return
@ -330,6 +335,12 @@ class ReplicationCommandHandler:
# between then and now.
missing_updates = cmd.token != current_token
while missing_updates:
logger.info(
"Fetching replication rows for '%s' between %i and %i",
stream_name,
current_token,
cmd.token,
)
(
updates,
current_token,
@ -343,13 +354,15 @@ class ReplicationCommandHandler:
for token, rows in _batch_updates(updates):
await self.on_rdata(
cmd.stream_name, token, [stream.parse_row(row) for row in rows],
stream_name, token, [stream.parse_row(row) for row in rows],
)
# We've now caught up to position sent to us, notify handler.
await self._replication_data_handler.on_position(cmd.stream_name, cmd.token)
logger.info("Caught up with stream '%s' to %i", stream_name, cmd.token)
self._streams_connected.add(cmd.stream_name)
# We've now caught up to position sent to us, notify handler.
await self._replication_data_handler.on_position(stream_name, cmd.token)
self._streams_by_connection.setdefault(conn, set()).add(stream_name)
async def on_REMOTE_SERVER_UP(
self, conn: AbstractConnection, cmd: RemoteServerUpCommand
@ -407,6 +420,12 @@ class ReplicationCommandHandler:
def lost_connection(self, connection: AbstractConnection):
"""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:

2
synapse/replication/tcp/redis.py
View File

@ -144,7 +144,7 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
Args:
cmd (Command)
"""
run_as_background_process("send-cmd", self._send_command, cmd)
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"""