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add a cache to have_seen_event (#9953) 

Empirically, this helped my server considerably when handling gaps in Matrix HQ. The problem was that we would repeatedly call have_seen_events for the same set of (50K or so) auth_events, each of which would take many minutes to complete, even though it's only an index scan.
This commit is contained in:
Richard van der Hoff 2021-06-01 12:04:47 +01:00 committed by GitHub
parent 10e6d2abce
commit b4b2fd2ece
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10 changed files with 206 additions and 21 deletions
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1
changelog.d/9953.feature Normal file
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@ -0,0 +1 @@
Improve performance of incoming federation transactions in large rooms.

1
changelog.d/9973.feature Normal file
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@ -0,0 +1 @@
Improve performance of incoming federation transactions in large rooms.

1
changelog.d/9973.misc
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@ -1 +0,0 @@
Make `LruCache.invalidate` support tree invalidation, and remove `invalidate_many`.

12
synapse/handlers/federation.py
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@ -577,7 +577,9 @@ class FederationHandler(BaseHandler):
# Fetch the state events from the DB, and check we have the auth events.
event_map = await self.store.get_events(state_event_ids, allow_rejected=True)
auth_events_in_store = await self.store.have_seen_events(auth_event_ids)
auth_events_in_store = await self.store.have_seen_events(
room_id, auth_event_ids
)
# Check for missing events. We handle state and auth event seperately,
# as we want to pull the state from the DB, but we don't for the auth
@ -610,7 +612,7 @@ class FederationHandler(BaseHandler):
if missing_auth_events:
auth_events_in_store = await self.store.have_seen_events(
missing_auth_events
room_id, missing_auth_events
)
missing_auth_events.difference_update(auth_events_in_store)
@ -710,7 +712,7 @@ class FederationHandler(BaseHandler):
missing_auth_events = set(auth_event_ids) - fetched_events.keys()
missing_auth_events.difference_update(
await self.store.have_seen_events(missing_auth_events)
await self.store.have_seen_events(room_id, missing_auth_events)
)
logger.debug("We are also missing %i auth events", len(missing_auth_events))
@ -2475,7 +2477,7 @@ class FederationHandler(BaseHandler):
#
# we start by checking if they are in the store, and then try calling /event_auth/.
if missing_auth:
have_events = await self.store.have_seen_events(missing_auth)
have_events = await self.store.have_seen_events(event.room_id, missing_auth)
logger.debug("Events %s are in the store", have_events)
missing_auth.difference_update(have_events)
@ -2494,7 +2496,7 @@ class FederationHandler(BaseHandler):
return context
seen_remotes = await self.store.have_seen_events(
[e.event_id for e in remote_auth_chain]
event.room_id, [e.event_id for e in remote_auth_chain]
)
for e in remote_auth_chain:

1
synapse/storage/databases/main/cache.py
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@ -168,6 +168,7 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
backfilled,
):
self._invalidate_get_event_cache(event_id)
self.have_seen_event.invalidate((room_id, event_id))
self.get_latest_event_ids_in_room.invalidate((room_id,))

63
synapse/storage/databases/main/events_worker.py
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@ -22,6 +22,7 @@ from typing import (
Iterable,
List,
Optional,
Set,
Tuple,
overload,
)
@ -55,7 +56,7 @@ from synapse.storage.engines import PostgresEngine
from synapse.storage.util.id_generators import MultiWriterIdGenerator, StreamIdGenerator
from synapse.storage.util.sequence import build_sequence_generator
from synapse.types import JsonDict, get_domain_from_id
from synapse.util.caches.descriptors import cached
from synapse.util.caches.descriptors import cached, cachedList
from synapse.util.caches.lrucache import LruCache
from synapse.util.iterutils import batch_iter
from synapse.util.metrics import Measure
@ -1045,32 +1046,74 @@ class EventsWorkerStore(SQLBaseStore):
return {r["event_id"] for r in rows}
async def have_seen_events(self, event_ids):
async def have_seen_events(
self, room_id: str, event_ids: Iterable[str]
) -> Set[str]:
"""Given a list of event ids, check if we have already processed them.
The room_id is only used to structure the cache (so that it can later be
invalidated by room_id) - there is no guarantee that the events are actually
in the room in question.
Args:
event_ids (iterable[str]):
room_id: Room we are polling
event_ids: events we are looking for
Returns:
set[str]: The events we have already seen.
"""
# if the event cache contains the event, obviously we've seen it.
results = {x for x in event_ids if self._get_event_cache.contains(x)}
res = await self._have_seen_events_dict(
(room_id, event_id) for event_id in event_ids
)
return {eid for ((_rid, eid), have_event) in res.items() if have_event}
def have_seen_events_txn(txn, chunk):
sql = "SELECT event_id FROM events as e WHERE "
@cachedList("have_seen_event", "keys")
async def _have_seen_events_dict(
self, keys: Iterable[Tuple[str, str]]
) -> Dict[Tuple[str, str], bool]:
"""Helper for have_seen_events
Returns:
a dict {(room_id, event_id)-> bool}
"""
# if the event cache contains the event, obviously we've seen it.
cache_results = {
(rid, eid) for (rid, eid) in keys if self._get_event_cache.contains((eid,))
}
results = {x: True for x in cache_results}
def have_seen_events_txn(txn, chunk: Tuple[Tuple[str, str], ...]):
# we deliberately do *not* query the database for room_id, to make the
# query an index-only lookup on `events_event_id_key`.
#
# We therefore pull the events from the database into a set...
sql = "SELECT event_id FROM events AS e WHERE "
clause, args = make_in_list_sql_clause(
txn.database_engine, "e.event_id", chunk
txn.database_engine, "e.event_id", [eid for (_rid, eid) in chunk]
)
txn.execute(sql + clause, args)
results.update(row[0] for row in txn)
found_events = {eid for eid, in txn}
for chunk in batch_iter((x for x in event_ids if x not in results), 100):
# ... and then we can update the results for each row in the batch
results.update({(rid, eid): (eid in found_events) for (rid, eid) in chunk})
# each batch requires its own index scan, so we make the batches as big as
# possible.
for chunk in batch_iter((k for k in keys if k not in cache_results), 500):
await self.db_pool.runInteraction(
"have_seen_events", have_seen_events_txn, chunk
)
return results
@cached(max_entries=100000, tree=True)
async def have_seen_event(self, room_id: str, event_id: str):
# this only exists for the benefit of the @cachedList descriptor on
# _have_seen_events_dict
raise NotImplementedError()
def _get_current_state_event_counts_txn(self, txn, room_id):
"""
See get_current_state_event_counts.

26
synapse/storage/databases/main/purge_events.py
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@ -16,14 +16,14 @@ import logging
from typing import Any, List, Set, Tuple
from synapse.api.errors import SynapseError
from synapse.storage._base import SQLBaseStore
from synapse.storage.databases.main import CacheInvalidationWorkerStore
from synapse.storage.databases.main.state import StateGroupWorkerStore
from synapse.types import RoomStreamToken
logger = logging.getLogger(__name__)
class PurgeEventsStore(StateGroupWorkerStore, SQLBaseStore):
class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
async def purge_history(
self, room_id: str, token: str, delete_local_events: bool
) -> Set[int]:
@ -203,8 +203,6 @@ class PurgeEventsStore(StateGroupWorkerStore, SQLBaseStore):
"DELETE FROM event_to_state_groups "
"WHERE event_id IN (SELECT event_id from events_to_purge)"
)
for event_id, _ in event_rows:
txn.call_after(self._get_state_group_for_event.invalidate, (event_id,))
# Delete all remote non-state events
for table in (
@ -283,6 +281,20 @@ class PurgeEventsStore(StateGroupWorkerStore, SQLBaseStore):
# so make sure to keep this actually last.
txn.execute("DROP TABLE events_to_purge")
for event_id, should_delete in event_rows:
self._invalidate_cache_and_stream(
txn, self._get_state_group_for_event, (event_id,)
)
# XXX: This is racy, since have_seen_events could be called between the
# transaction completing and the invalidation running. On the other hand,
# that's no different to calling `have_seen_events` just before the
# event is deleted from the database.
if should_delete:
self._invalidate_cache_and_stream(
txn, self.have_seen_event, (room_id, event_id)
)
logger.info("[purge] done")
return referenced_state_groups
@ -422,7 +434,11 @@ class PurgeEventsStore(StateGroupWorkerStore, SQLBaseStore):
# index on them. In any case we should be clearing out 'stream' tables
# periodically anyway (#5888)
# TODO: we could probably usefully do a bunch of cache invalidation here
# TODO: we could probably usefully do a bunch more cache invalidation here
# XXX: as with purge_history, this is racy, but no worse than other races
# that already exist.
self._invalidate_cache_and_stream(txn, self.have_seen_event, (room_id,))
logger.info("[purge] done")

13
tests/storage/databases/__init__.py Normal file
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@ -0,0 +1,13 @@
# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

13
tests/storage/databases/main/__init__.py Normal file
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@ -0,0 +1,13 @@
# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

96
tests/storage/databases/main/test_events_worker.py Normal file
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@ -0,0 +1,96 @@
# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import json
from synapse.logging.context import LoggingContext
from synapse.storage.databases.main.events_worker import EventsWorkerStore
from tests import unittest
class HaveSeenEventsTestCase(unittest.HomeserverTestCase):
def prepare(self, reactor, clock, hs):
self.store: EventsWorkerStore = hs.get_datastore()
# insert some test data
for rid in ("room1", "room2"):
self.get_success(
self.store.db_pool.simple_insert(
"rooms",
{"room_id": rid, "room_version": 4},
)
)
for idx, (rid, eid) in enumerate(
(
("room1", "event10"),
("room1", "event11"),
("room1", "event12"),
("room2", "event20"),
)
):
self.get_success(
self.store.db_pool.simple_insert(
"events",
{
"event_id": eid,
"room_id": rid,
"topological_ordering": idx,
"stream_ordering": idx,
"type": "test",
"processed": True,
"outlier": False,
},
)
)
self.get_success(
self.store.db_pool.simple_insert(
"event_json",
{
"event_id": eid,
"room_id": rid,
"json": json.dumps({"type": "test", "room_id": rid}),
"internal_metadata": "{}",
"format_version": 3,
},
)
)
def test_simple(self):
with LoggingContext(name="test") as ctx:
res = self.get_success(
self.store.have_seen_events("room1", ["event10", "event19"])
)
self.assertEquals(res, {"event10"})
# that should result in a single db query
self.assertEquals(ctx.get_resource_usage().db_txn_count, 1)
# a second lookup of the same events should cause no queries
with LoggingContext(name="test") as ctx:
res = self.get_success(
self.store.have_seen_events("room1", ["event10", "event19"])
)
self.assertEquals(res, {"event10"})
self.assertEquals(ctx.get_resource_usage().db_txn_count, 0)
def test_query_via_event_cache(self):
# fetch an event into the event cache
self.get_success(self.store.get_event("event10"))
# looking it up should now cause no db hits
with LoggingContext(name="test") as ctx:
res = self.get_success(self.store.have_seen_events("room1", ["event10"]))
self.assertEquals(res, {"event10"})
self.assertEquals(ctx.get_resource_usage().db_txn_count, 0)