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synced 2024-10-01 01:36:05 -04:00
Speed up fetching latest stream positions via cache (#17606)
The idea is to engineer it so that the vast majority of the rooms can stay in the cache, so we can just ignore them.
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changelog.d/17606.misc
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1
changelog.d/17606.misc
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@ -0,0 +1 @@
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Speed up incremental syncs in sliding sync by adding some more caching.
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@ -313,6 +313,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
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"get_unread_event_push_actions_by_room_for_user", (room_id,)
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)
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self._attempt_to_invalidate_cache("_get_max_event_pos", (room_id,))
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# The `_get_membership_from_event_id` is immutable, except for the
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# case where we look up an event *before* persisting it.
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self._attempt_to_invalidate_cache("_get_membership_from_event_id", (event_id,))
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@ -404,6 +406,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
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)
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self._attempt_to_invalidate_cache("get_relations_for_event", (room_id,))
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self._attempt_to_invalidate_cache("_get_max_event_pos", (room_id,))
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self._attempt_to_invalidate_cache("_get_membership_from_event_id", None)
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self._attempt_to_invalidate_cache("get_applicable_edit", None)
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self._attempt_to_invalidate_cache("get_thread_id", None)
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@ -476,6 +480,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
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self._attempt_to_invalidate_cache("get_room_type", (room_id,))
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self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))
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self._attempt_to_invalidate_cache("_get_max_event_pos", (room_id,))
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# And delete state caches.
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self._invalidate_state_caches_all(room_id)
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@ -50,6 +50,7 @@ from typing import (
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Dict,
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Iterable,
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List,
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Mapping,
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Optional,
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Protocol,
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Set,
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@ -80,7 +81,7 @@ from synapse.storage.databases.main.events_worker import EventsWorkerStore
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from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
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from synapse.storage.util.id_generators import MultiWriterIdGenerator
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from synapse.types import PersistedEventPosition, RoomStreamToken, StrCollection
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from synapse.util.caches.descriptors import cached
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from synapse.util.caches.descriptors import cached, cachedList
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from synapse.util.caches.stream_change_cache import StreamChangeCache
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from synapse.util.cancellation import cancellable
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from synapse.util.iterutils import batch_iter
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@ -1381,8 +1382,52 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
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rooms
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"""
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# First we just get the latest positions for the room, as the vast
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# majority of them will be before the given end token anyway. By doing
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# this we can cache most rooms.
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uncapped_results = await self._bulk_get_max_event_pos(room_ids)
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# Check that the stream position for the rooms are from before the
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# minimum position of the token. If not then we need to fetch more
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# rows.
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results: Dict[str, int] = {}
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recheck_rooms: Set[str] = set()
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min_token = end_token.stream
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max_token = end_token.get_max_stream_pos()
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for room_id, stream in uncapped_results.items():
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if stream <= min_token:
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results[room_id] = stream
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else:
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recheck_rooms.add(room_id)
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if not recheck_rooms:
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return results
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# There shouldn't be many rooms that we need to recheck, so we do them
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# one-by-one.
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for room_id in recheck_rooms:
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result = await self.get_last_event_pos_in_room_before_stream_ordering(
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room_id, end_token
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)
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if result is not None:
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results[room_id] = result[1].stream
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return results
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@cached()
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async def _get_max_event_pos(self, room_id: str) -> int:
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raise NotImplementedError()
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@cachedList(cached_method_name="_get_max_event_pos", list_name="room_ids")
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async def _bulk_get_max_event_pos(
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self, room_ids: StrCollection
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) -> Mapping[str, int]:
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"""Fetch the max position of a persisted event in the room."""
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# We need to be careful not to return positions ahead of the current
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# positions, so we get the current token now and cap our queries to it.
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now_token = self.get_room_max_token()
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max_pos = now_token.get_max_stream_pos()
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results: Dict[str, int] = {}
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# First, we check for the rooms in the stream change cache to see if we
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@ -1390,31 +1435,32 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
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missing_room_ids: Set[str] = set()
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for room_id in room_ids:
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stream_pos = self._events_stream_cache.get_max_pos_of_last_change(room_id)
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if stream_pos and stream_pos <= min_token:
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if stream_pos is not None:
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results[room_id] = stream_pos
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else:
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missing_room_ids.add(room_id)
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if not missing_room_ids:
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return results
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# Next, we query the stream position from the DB. At first we fetch all
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# positions less than the *max* stream pos in the token, then filter
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# them down. We do this as a) this is a cheaper query, and b) the vast
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# majority of rooms will have a latest token from before the min stream
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# pos.
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def bulk_get_last_event_pos_txn(
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txn: LoggingTransaction, batch_room_ids: StrCollection
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def bulk_get_max_event_pos_txn(
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txn: LoggingTransaction, batched_room_ids: StrCollection
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) -> Dict[str, int]:
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# This query fetches the latest stream position in the rooms before
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# the given max position.
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clause, args = make_in_list_sql_clause(
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self.database_engine, "room_id", batch_room_ids
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self.database_engine, "room_id", batched_room_ids
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)
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sql = f"""
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SELECT room_id, (
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SELECT stream_ordering FROM events AS e
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LEFT JOIN rejections USING (event_id)
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WHERE e.room_id = r.room_id
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AND stream_ordering <= ?
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AND e.stream_ordering <= ?
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AND NOT outlier
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AND rejection_reason IS NULL
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ORDER BY stream_ordering DESC
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@ -1423,72 +1469,29 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
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FROM rooms AS r
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WHERE {clause}
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"""
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txn.execute(sql, [max_token] + args)
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txn.execute(sql, [max_pos] + args)
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return {row[0]: row[1] for row in txn}
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recheck_rooms: Set[str] = set()
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for batched in batch_iter(missing_room_ids, 1000):
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result = await self.db_pool.runInteraction(
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"bulk_get_last_event_pos_in_room_before_stream_ordering",
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bulk_get_last_event_pos_txn,
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batched,
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for batched in batch_iter(room_ids, 1000):
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batch_results = await self.db_pool.runInteraction(
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"_bulk_get_max_event_pos", bulk_get_max_event_pos_txn, batched
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)
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# Check that the stream position for the rooms are from before the
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# minimum position of the token. If not then we need to fetch more
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# rows.
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for room_id, stream in result.items():
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if stream <= min_token:
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results[room_id] = stream
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for room_id, stream_ordering in batch_results.items():
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if stream_ordering <= now_token.stream:
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results.update(batch_results)
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else:
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recheck_rooms.add(room_id)
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if not recheck_rooms:
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return results
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# For the remaining rooms we need to fetch all rows between the min and
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# max stream positions in the end token, and filter out the rows that
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# are after the end token.
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#
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# This query should be fast as the range between the min and max should
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# be small.
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def bulk_get_last_event_pos_recheck_txn(
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txn: LoggingTransaction, batch_room_ids: StrCollection
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) -> Dict[str, int]:
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clause, args = make_in_list_sql_clause(
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self.database_engine, "room_id", batch_room_ids
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# We now need to handle rooms where the above query returned a stream
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# position that was potentially too new. This should happen very rarely
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# so we just query the rooms one-by-one
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for room_id in recheck_rooms:
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result = await self.get_last_event_pos_in_room_before_stream_ordering(
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room_id, now_token
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)
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sql = f"""
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SELECT room_id, instance_name, stream_ordering
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FROM events
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WHERE ? < stream_ordering AND stream_ordering <= ?
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AND NOT outlier
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AND rejection_reason IS NULL
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AND {clause}
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ORDER BY stream_ordering ASC
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"""
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txn.execute(sql, [min_token, max_token] + args)
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# We take the max stream ordering that is less than the token. Since
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# we ordered by stream ordering we just need to iterate through and
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# take the last matching stream ordering.
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txn_results: Dict[str, int] = {}
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for row in txn:
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room_id = row[0]
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event_pos = PersistedEventPosition(row[1], row[2])
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if not event_pos.persisted_after(end_token):
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txn_results[room_id] = event_pos.stream
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return txn_results
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for batched in batch_iter(recheck_rooms, 1000):
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recheck_result = await self.db_pool.runInteraction(
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"bulk_get_last_event_pos_in_room_before_stream_ordering_recheck",
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bulk_get_last_event_pos_recheck_txn,
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batched,
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)
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results.update(recheck_result)
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if result is not None:
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results[room_id] = result[1].stream
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return results
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