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https://git.anonymousland.org/anonymousland/synapse-product.git
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7ee24c5674
Before all streams were only written to from master, so only master needed to respond to `REPLICATE` commands. Before all instances wrote to the cache invalidation stream, but didn't respond to `REPLICATE`. This was a bug, which could lead to missed rows from cache invalidation stream if an instance is restarted, however all the caches would be empty in that case so it wasn't a problem.
208 lines
7.6 KiB
Python
208 lines
7.6 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2017 Vector Creations Ltd
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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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"""The server side of the replication stream.
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"""
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import logging
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import random
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from prometheus_client import Counter
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from twisted.internet.protocol import Factory
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.replication.tcp.protocol import ServerReplicationStreamProtocol
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from synapse.util.metrics import Measure
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stream_updates_counter = Counter(
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"synapse_replication_tcp_resource_stream_updates", "", ["stream_name"]
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)
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logger = logging.getLogger(__name__)
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class ReplicationStreamProtocolFactory(Factory):
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"""Factory for new replication connections.
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"""
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def __init__(self, hs):
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self.command_handler = hs.get_tcp_replication()
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self.clock = hs.get_clock()
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self.server_name = hs.config.server_name
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# If we've created a `ReplicationStreamProtocolFactory` then we're
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# almost certainly registering a replication listener, so let's ensure
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# that we've started a `ReplicationStreamer` instance to actually push
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# data.
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#
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# (This is a bit of a weird place to do this, but the alternatives such
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# as putting this in `HomeServer.setup()`, requires either passing the
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# listener config again or always starting a `ReplicationStreamer`.)
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hs.get_replication_streamer()
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def buildProtocol(self, addr):
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return ServerReplicationStreamProtocol(
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self.server_name, self.clock, self.command_handler
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)
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class ReplicationStreamer(object):
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"""Handles replication connections.
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This needs to be poked when new replication data may be available. When new
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data is available it will propagate to all connected clients.
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"""
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def __init__(self, hs):
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self.store = hs.get_datastore()
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self.clock = hs.get_clock()
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self.notifier = hs.get_notifier()
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self._instance_name = hs.get_instance_name()
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self._replication_torture_level = hs.config.replication_torture_level
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self.notifier.add_replication_callback(self.on_notifier_poke)
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# Keeps track of whether we are currently checking for updates
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self.is_looping = False
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self.pending_updates = False
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self.command_handler = hs.get_tcp_replication()
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# Set of streams to replicate.
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self.streams = self.command_handler.get_streams_to_replicate()
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def on_notifier_poke(self):
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"""Checks if there is actually any new data and sends it to the
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connections if there are.
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This should get called each time new data is available, even if it
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is currently being executed, so that nothing gets missed
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"""
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if not self.command_handler.connected():
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# Don't bother if nothing is listening. We still need to advance
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# the stream tokens otherwise they'll fall beihind forever
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for stream in self.streams:
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stream.discard_updates_and_advance()
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return
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self.pending_updates = True
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if self.is_looping:
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logger.debug("Notifier poke loop already running")
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return
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run_as_background_process("replication_notifier", self._run_notifier_loop)
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async def _run_notifier_loop(self):
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self.is_looping = True
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try:
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# Keep looping while there have been pokes about potential updates.
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# This protects against the race where a stream we already checked
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# gets an update while we're handling other streams.
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while self.pending_updates:
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self.pending_updates = False
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with Measure(self.clock, "repl.stream.get_updates"):
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all_streams = self.streams
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if self._replication_torture_level is not None:
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# there is no guarantee about ordering between the streams,
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# so let's shuffle them around a bit when we are in torture mode.
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all_streams = list(all_streams)
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random.shuffle(all_streams)
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for stream in all_streams:
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if stream.last_token == stream.current_token(
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self._instance_name
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):
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continue
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if self._replication_torture_level:
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await self.clock.sleep(
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self._replication_torture_level / 1000.0
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)
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logger.debug(
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"Getting stream: %s: %s -> %s",
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stream.NAME,
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stream.last_token,
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stream.current_token(self._instance_name),
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)
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try:
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updates, current_token, limited = await stream.get_updates()
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self.pending_updates |= limited
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except Exception:
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logger.info("Failed to handle stream %s", stream.NAME)
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raise
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logger.debug(
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"Sending %d updates", len(updates),
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)
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if updates:
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logger.info(
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"Streaming: %s -> %s", stream.NAME, updates[-1][0]
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)
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stream_updates_counter.labels(stream.NAME).inc(len(updates))
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# Some streams return multiple rows with the same stream IDs,
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# we need to make sure they get sent out in batches. We do
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# this by setting the current token to all but the last of
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# a series of updates with the same token to have a None
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# token. See RdataCommand for more details.
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batched_updates = _batch_updates(updates)
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for token, row in batched_updates:
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try:
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self.command_handler.stream_update(
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stream.NAME, token, row
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)
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except Exception:
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logger.exception("Failed to replicate")
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logger.debug("No more pending updates, breaking poke loop")
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finally:
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self.pending_updates = False
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self.is_looping = False
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def _batch_updates(updates):
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"""Takes a list of updates of form [(token, row)] and sets the token to
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None for all rows where the next row has the same token. This is used to
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implement batching.
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For example:
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[(1, _), (1, _), (2, _), (3, _), (3, _)]
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becomes:
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[(None, _), (1, _), (2, _), (None, _), (3, _)]
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"""
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if not updates:
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return []
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new_updates = []
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for i, update in enumerate(updates[:-1]):
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if update[0] == updates[i + 1][0]:
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new_updates.append((None, update[1]))
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else:
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new_updates.append(update)
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new_updates.append(updates[-1])
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return new_updates
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