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f5668f0b4a
When we join a room via the faster-joins mechanism, we end up with "partial state" at some points on the event DAG. Many parts of the codebase need to wait for the full state to load. So, we implement a mechanism to keep track of which events have partial state, and wait for them to be fully-populated.
121 lines
4.7 KiB
Python
121 lines
4.7 KiB
Python
# Copyright 2022 The Matrix.org Foundation C.I.C.
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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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import logging
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from collections import defaultdict
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from typing import Collection, Dict, Set
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from twisted.internet import defer
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from twisted.internet.defer import Deferred
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from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
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from synapse.storage.databases.main.events_worker import EventsWorkerStore
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from synapse.util import unwrapFirstError
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logger = logging.getLogger(__name__)
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class PartialStateEventsTracker:
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"""Keeps track of which events have partial state, after a partial-state join"""
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def __init__(self, store: EventsWorkerStore):
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self._store = store
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# a map from event id to a set of Deferreds which are waiting for that event to be
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# un-partial-stated.
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self._observers: Dict[str, Set[Deferred[None]]] = defaultdict(set)
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def notify_un_partial_stated(self, event_id: str) -> None:
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"""Notify that we now have full state for a given event
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Called by the state-resynchronization loop whenever we resynchronize the state
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for a particular event. Unblocks any callers to await_full_state() for that
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event.
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Args:
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event_id: the event that now has full state.
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"""
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observers = self._observers.pop(event_id, None)
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if not observers:
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return
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logger.info(
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"Notifying %i things waiting for un-partial-stating of event %s",
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len(observers),
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event_id,
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)
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with PreserveLoggingContext():
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for o in observers:
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o.callback(None)
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async def await_full_state(self, event_ids: Collection[str]) -> None:
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"""Wait for all the given events to have full state.
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Args:
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event_ids: the list of event ids that we want full state for
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"""
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# first try the happy path: if there are no partial-state events, we can return
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# quickly
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partial_state_event_ids = [
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ev
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for ev, p in (await self._store.get_partial_state_events(event_ids)).items()
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if p
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]
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if not partial_state_event_ids:
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return
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logger.info(
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"Awaiting un-partial-stating of events %s",
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partial_state_event_ids,
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stack_info=True,
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)
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# create an observer for each lazy-joined event
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observers: Dict[str, Deferred[None]] = {
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event_id: Deferred() for event_id in partial_state_event_ids
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}
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for event_id, observer in observers.items():
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self._observers[event_id].add(observer)
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try:
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# some of them may have been un-lazy-joined between us checking the db and
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# registering the observer, in which case we'd wait forever for the
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# notification. Call back the observers now.
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for event_id, partial in (
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await self._store.get_partial_state_events(observers.keys())
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).items():
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# there may have been a call to notify_un_partial_stated during the
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# db query, so the observers may already have been called.
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if not partial and not observers[event_id].called:
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observers[event_id].callback(None)
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await make_deferred_yieldable(
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defer.gatherResults(
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observers.values(),
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consumeErrors=True,
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)
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).addErrback(unwrapFirstError)
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logger.info("Events %s all un-partial-stated", observers.keys())
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finally:
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# remove any observers we created. This should happen when the notification
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# is received, but that might not happen for two reasons:
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# (a) we're bailing out early on an exception (including us being
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# cancelled during the await)
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# (b) the event got de-lazy-joined before we set up the observer.
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for event_id, observer in observers.items():
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observer_set = self._observers.get(event_id)
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if observer_set:
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observer_set.discard(observer)
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if not observer_set:
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del self._observers[event_id]
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