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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.
This commit is contained in:
Erik Johnston 2024-08-27 12:03:56 +01:00 committed by GitHub
parent b4d95409fb
commit defd4aca67
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3 changed files with 77 additions and 67 deletions
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1
changelog.d/17606.misc Normal file
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@ -0,0 +1 @@
Speed up incremental syncs in sliding sync by adding some more caching.

6
synapse/storage/databases/main/cache.py
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@ -313,6 +313,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
"get_unread_event_push_actions_by_room_for_user", (room_id,)
)
self._attempt_to_invalidate_cache("_get_max_event_pos", (room_id,))
# The `_get_membership_from_event_id` is immutable, except for the
# case where we look up an event *before* persisting it.
self._attempt_to_invalidate_cache("_get_membership_from_event_id", (event_id,))
@ -404,6 +406,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
)
self._attempt_to_invalidate_cache("get_relations_for_event", (room_id,))
self._attempt_to_invalidate_cache("_get_max_event_pos", (room_id,))
self._attempt_to_invalidate_cache("_get_membership_from_event_id", None)
self._attempt_to_invalidate_cache("get_applicable_edit", None)
self._attempt_to_invalidate_cache("get_thread_id", None)
@ -476,6 +480,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
self._attempt_to_invalidate_cache("get_room_type", (room_id,))
self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))
self._attempt_to_invalidate_cache("_get_max_event_pos", (room_id,))
# And delete state caches.
self._invalidate_state_caches_all(room_id)

181
synapse/storage/databases/main/stream.py
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@ -50,6 +50,7 @@ from typing import (
Dict,
Iterable,
List,
Mapping,
Optional,
Protocol,
Set,
@ -80,7 +81,7 @@ from synapse.storage.databases.main.events_worker import EventsWorkerStore
from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
from synapse.storage.util.id_generators import MultiWriterIdGenerator
from synapse.types import PersistedEventPosition, RoomStreamToken, StrCollection
from synapse.util.caches.descriptors import cached
from synapse.util.caches.descriptors import cached, cachedList
from synapse.util.caches.stream_change_cache import StreamChangeCache
from synapse.util.cancellation import cancellable
from synapse.util.iterutils import batch_iter
@ -1381,63 +1382,18 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
rooms
"""
min_token = end_token.stream
max_token = end_token.get_max_stream_pos()
results: Dict[str, int] = {}
# First, we check for the rooms in the stream change cache to see if we
# can just use the latest position from it.
missing_room_ids: Set[str] = set()
for room_id in room_ids:
stream_pos = self._events_stream_cache.get_max_pos_of_last_change(room_id)
if stream_pos and stream_pos <= min_token:
results[room_id] = stream_pos
else:
missing_room_ids.add(room_id)
# Next, we query the stream position from the DB. At first we fetch all
# positions less than the *max* stream pos in the token, then filter
# them down. We do this as a) this is a cheaper query, and b) the vast
# majority of rooms will have a latest token from before the min stream
# pos.
def bulk_get_last_event_pos_txn(
txn: LoggingTransaction, batch_room_ids: StrCollection
) -> Dict[str, int]:
# This query fetches the latest stream position in the rooms before
# the given max position.
clause, args = make_in_list_sql_clause(
self.database_engine, "room_id", batch_room_ids
)
sql = f"""
SELECT room_id, (
SELECT stream_ordering FROM events AS e
LEFT JOIN rejections USING (event_id)
WHERE e.room_id = r.room_id
AND stream_ordering <= ?
AND NOT outlier
AND rejection_reason IS NULL
ORDER BY stream_ordering DESC
LIMIT 1
)
FROM rooms AS r
WHERE {clause}
"""
txn.execute(sql, [max_token] + args)
return {row[0]: row[1] for row in txn}
recheck_rooms: Set[str] = set()
for batched in batch_iter(missing_room_ids, 1000):
result = await self.db_pool.runInteraction(
"bulk_get_last_event_pos_in_room_before_stream_ordering",
bulk_get_last_event_pos_txn,
batched,
)
# First we just get the latest positions for the room, as the vast
# majority of them will be before the given end token anyway. By doing
# this we can cache most rooms.
uncapped_results = await self._bulk_get_max_event_pos(room_ids)
# Check that the stream position for the rooms are from before the
# minimum position of the token. If not then we need to fetch more
# rows.
for room_id, stream in result.items():
results: Dict[str, int] = {}
recheck_rooms: Set[str] = set()
min_token = end_token.stream
for room_id, stream in uncapped_results.items():
if stream <= min_token:
results[room_id] = stream
else:
@ -1446,49 +1402,96 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
if not recheck_rooms:
return results
# For the remaining rooms we need to fetch all rows between the min and
# max stream positions in the end token, and filter out the rows that
# are after the end token.
#
# This query should be fast as the range between the min and max should
# be small.
# There shouldn't be many rooms that we need to recheck, so we do them
# one-by-one.
for room_id in recheck_rooms:
result = await self.get_last_event_pos_in_room_before_stream_ordering(
room_id, end_token
)
if result is not None:
results[room_id] = result[1].stream
def bulk_get_last_event_pos_recheck_txn(
txn: LoggingTransaction, batch_room_ids: StrCollection
return results
@cached()
async def _get_max_event_pos(self, room_id: str) -> int:
raise NotImplementedError()
@cachedList(cached_method_name="_get_max_event_pos", list_name="room_ids")
async def _bulk_get_max_event_pos(
self, room_ids: StrCollection
) -> Mapping[str, int]:
"""Fetch the max position of a persisted event in the room."""
# We need to be careful not to return positions ahead of the current
# positions, so we get the current token now and cap our queries to it.
now_token = self.get_room_max_token()
max_pos = now_token.get_max_stream_pos()
results: Dict[str, int] = {}
# First, we check for the rooms in the stream change cache to see if we
# can just use the latest position from it.
missing_room_ids: Set[str] = set()
for room_id in room_ids:
stream_pos = self._events_stream_cache.get_max_pos_of_last_change(room_id)
if stream_pos is not None:
results[room_id] = stream_pos
else:
missing_room_ids.add(room_id)
if not missing_room_ids:
return results
# Next, we query the stream position from the DB. At first we fetch all
# positions less than the *max* stream pos in the token, then filter
# them down. We do this as a) this is a cheaper query, and b) the vast
# majority of rooms will have a latest token from before the min stream
# pos.
def bulk_get_max_event_pos_txn(
txn: LoggingTransaction, batched_room_ids: StrCollection
) -> Dict[str, int]:
clause, args = make_in_list_sql_clause(
self.database_engine, "room_id", batch_room_ids
self.database_engine, "room_id", batched_room_ids
)
sql = f"""
SELECT room_id, instance_name, stream_ordering
FROM events
WHERE ? < stream_ordering AND stream_ordering <= ?
SELECT room_id, (
SELECT stream_ordering FROM events AS e
LEFT JOIN rejections USING (event_id)
WHERE e.room_id = r.room_id
AND e.stream_ordering <= ?
AND NOT outlier
AND rejection_reason IS NULL
AND {clause}
ORDER BY stream_ordering ASC
"""
txn.execute(sql, [min_token, max_token] + args)
# We take the max stream ordering that is less than the token. Since
# we ordered by stream ordering we just need to iterate through and
# take the last matching stream ordering.
txn_results: Dict[str, int] = {}
for row in txn:
room_id = row[0]
event_pos = PersistedEventPosition(row[1], row[2])
if not event_pos.persisted_after(end_token):
txn_results[room_id] = event_pos.stream
return txn_results
for batched in batch_iter(recheck_rooms, 1000):
recheck_result = await self.db_pool.runInteraction(
"bulk_get_last_event_pos_in_room_before_stream_ordering_recheck",
bulk_get_last_event_pos_recheck_txn,
batched,
ORDER BY stream_ordering DESC
LIMIT 1
)
results.update(recheck_result)
FROM rooms AS r
WHERE {clause}
"""
txn.execute(sql, [max_pos] + args)
return {row[0]: row[1] for row in txn}
recheck_rooms: Set[str] = set()
for batched in batch_iter(room_ids, 1000):
batch_results = await self.db_pool.runInteraction(
"_bulk_get_max_event_pos", bulk_get_max_event_pos_txn, batched
)
for room_id, stream_ordering in batch_results.items():
if stream_ordering <= now_token.stream:
results.update(batch_results)
else:
recheck_rooms.add(room_id)
# We now need to handle rooms where the above query returned a stream
# position that was potentially too new. This should happen very rarely
# so we just query the rooms one-by-one
for room_id in recheck_rooms:
result = await self.get_last_event_pos_in_room_before_stream_ordering(
room_id, now_token
)
if result is not None:
results[room_id] = result[1].stream
return results