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Fix have_seen_event cache not being invalidated (#13863)

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Fix https://github.com/matrix-org/synapse/issues/13856
Fix https://github.com/matrix-org/synapse/issues/13865

> Discovered while trying to make Synapse fast enough for [this MSC2716 test for importing many batches](https://github.com/matrix-org/complement/pull/214#discussion_r741678240). As an example, disabling the `have_seen_event` cache saves 10 seconds for each `/messages` request in that MSC2716 Complement test because we're not making as many federation requests for `/state` (speeding up `have_seen_event` itself is related to https://github.com/matrix-org/synapse/issues/13625) 
> 
> But this will also make `/messages` faster in general so we can include it in the [faster `/messages` milestone](https://github.com/matrix-org/synapse/milestone/11).
> 
> *-- https://github.com/matrix-org/synapse/issues/13856*


### The problem

`_invalidate_caches_for_event` doesn't run in monolith mode which means we never even tried to clear the `have_seen_event` and other caches. And even in worker mode, it only runs on the workers, not the master (AFAICT).

Additionally there was bug with the key being wrong so `_invalidate_caches_for_event` never invalidates the `have_seen_event` cache even when it does run.

Because we were using the `@cachedList` wrong, it was putting items in the cache under keys like `((room_id, event_id),)` with a `set` in a `set` (ex. `(('!TnCIJPKzdQdUlIyXdQ:test', '$Iu0eqEBN7qcyF1S9B3oNB3I91v2o5YOgRNPwi_78s-k'),)`) and we we're trying to invalidate with just `(room_id, event_id)` which did nothing.
This commit is contained in:
Eric Eastwood 2022-09-27 15:55:43 -05:00 committed by GitHub
parent 35e9d6a616
commit 29269d9d3f
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5 changed files with 165 additions and 67 deletions
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1
changelog.d/13863.bugfix Normal file
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@ -0,0 +1 @@
Fix `have_seen_event` cache not being invalidated after we persist an event which causes inefficiency effects like extra `/state` federation calls.

40
synapse/storage/databases/main/events_worker.py
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@ -1474,32 +1474,38 @@ class EventsWorkerStore(SQLBaseStore):
# the batches as big as possible.
results: Set[str] = set()
for chunk in batch_iter(event_ids, 500):
r = await self._have_seen_events_dict(
[(room_id, event_id) for event_id in chunk]
for event_ids_chunk in batch_iter(event_ids, 500):
events_seen_dict = await self._have_seen_events_dict(
room_id, event_ids_chunk
)
results.update(
eid for (eid, have_event) in events_seen_dict.items() if have_event
)
results.update(eid for ((_rid, eid), have_event) in r.items() if have_event)
return results
@cachedList(cached_method_name="have_seen_event", list_name="keys")
@cachedList(cached_method_name="have_seen_event", list_name="event_ids")
async def _have_seen_events_dict(
self, keys: Collection[Tuple[str, str]]
) -> Dict[Tuple[str, str], bool]:
self,
room_id: str,
event_ids: Collection[str],
) -> Dict[str, bool]:
"""Helper for have_seen_events
Returns:
a dict {(room_id, event_id)-> bool}
a dict {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 await self._get_event_cache.contains((eid,))
event_id
for event_id in event_ids
if await self._get_event_cache.contains((event_id,))
}
results = dict.fromkeys(cache_results, True)
remaining = [k for k in keys if k not in cache_results]
remaining = [
event_id for event_id in event_ids if event_id not in cache_results
]
if not remaining:
return results
@ -1511,23 +1517,21 @@ class EventsWorkerStore(SQLBaseStore):
sql = "SELECT event_id FROM events AS e WHERE "
clause, args = make_in_list_sql_clause(
txn.database_engine, "e.event_id", [eid for (_rid, eid) in remaining]
txn.database_engine, "e.event_id", remaining
)
txn.execute(sql + clause, args)
found_events = {eid for eid, in txn}
# ... and then we can update the results for each key
results.update(
{(rid, eid): (eid in found_events) for (rid, eid) in remaining}
)
results.update({eid: (eid in found_events) for eid in remaining})
await self.db_pool.runInteraction("have_seen_events", have_seen_events_txn)
return results
@cached(max_entries=100000, tree=True)
async def have_seen_event(self, room_id: str, event_id: str) -> bool:
res = await self._have_seen_events_dict(((room_id, event_id),))
return res[(room_id, event_id)]
res = await self._have_seen_events_dict(room_id, [event_id])
return res[event_id]
def _get_current_state_event_counts_txn(
self, txn: LoggingTransaction, room_id: str

6
synapse/util/caches/descriptors.py
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@ -431,6 +431,12 @@ class DeferredCacheListDescriptor(_CacheDescriptorBase):
cache: DeferredCache[CacheKey, Any] = cached_method.cache
num_args = cached_method.num_args
if num_args != self.num_args:
raise Exception(
"Number of args (%s) does not match underlying cache_method_name=%s (%s)."
% (self.num_args, self.cached_method_name, num_args)
)
@functools.wraps(self.orig)
def wrapped(*args: Any, **kwargs: Any) -> "defer.Deferred[Dict]":
# If we're passed a cache_context then we'll want to call its

152
tests/storage/databases/main/test_events_worker.py
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@ -35,66 +35,45 @@ from synapse.util import Clock
from synapse.util.async_helpers import yieldable_gather_results
from tests import unittest
from tests.test_utils.event_injection import create_event, inject_event
class HaveSeenEventsTestCase(unittest.HomeserverTestCase):
servlets = [
admin.register_servlets,
room.register_servlets,
login.register_servlets,
]
def prepare(self, reactor, clock, hs):
self.hs = hs
self.store: EventsWorkerStore = hs.get_datastores().main
# 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},
)
)
self.user = self.register_user("user", "pass")
self.token = self.login(self.user, "pass")
self.room_id = self.helper.create_room_as(self.user, tok=self.token)
self.event_ids: List[str] = []
for idx, rid in enumerate(
(
"room1",
"room1",
"room1",
"room2",
for i in range(3):
event = self.get_success(
inject_event(
hs,
room_version=RoomVersions.V7.identifier,
room_id=self.room_id,
sender=self.user,
type="test_event_type",
content={"body": f"foobarbaz{i}"},
)
)
):
event_json = {"type": f"test {idx}", "room_id": rid}
event = make_event_from_dict(event_json, room_version=RoomVersions.V4)
event_id = event.event_id
self.get_success(
self.store.db_pool.simple_insert(
"events",
{
"event_id": event_id,
"room_id": rid,
"topological_ordering": idx,
"stream_ordering": idx,
"type": event.type,
"processed": True,
"outlier": False,
},
)
)
self.get_success(
self.store.db_pool.simple_insert(
"event_json",
{
"event_id": event_id,
"room_id": rid,
"json": json.dumps(event_json),
"internal_metadata": "{}",
"format_version": 3,
},
)
)
self.event_ids.append(event_id)
self.event_ids.append(event.event_id)
def test_simple(self):
with LoggingContext(name="test") as ctx:
res = self.get_success(
self.store.have_seen_events("room1", [self.event_ids[0], "event19"])
self.store.have_seen_events(
self.room_id, [self.event_ids[0], "eventdoesnotexist"]
)
)
self.assertEqual(res, {self.event_ids[0]})
@ -104,7 +83,9 @@ class HaveSeenEventsTestCase(unittest.HomeserverTestCase):
# 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", [self.event_ids[0], "event19"])
self.store.have_seen_events(
self.room_id, [self.event_ids[0], "eventdoesnotexist"]
)
)
self.assertEqual(res, {self.event_ids[0]})
self.assertEqual(ctx.get_resource_usage().db_txn_count, 0)
@ -116,11 +97,86 @@ class HaveSeenEventsTestCase(unittest.HomeserverTestCase):
# 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", [self.event_ids[0]])
self.store.have_seen_events(self.room_id, [self.event_ids[0]])
)
self.assertEqual(res, {self.event_ids[0]})
self.assertEqual(ctx.get_resource_usage().db_txn_count, 0)
def test_persisting_event_invalidates_cache(self):
"""
Test to make sure that the `have_seen_event` cache
is invalidated after we persist an event and returns
the updated value.
"""
event, event_context = self.get_success(
create_event(
self.hs,
room_id=self.room_id,
sender=self.user,
type="test_event_type",
content={"body": "garply"},
)
)
with LoggingContext(name="test") as ctx:
# First, check `have_seen_event` for an event we have not seen yet
# to prime the cache with a `false` value.
res = self.get_success(
self.store.have_seen_events(event.room_id, [event.event_id])
)
self.assertEqual(res, set())
# That should result in a single db query to lookup
self.assertEqual(ctx.get_resource_usage().db_txn_count, 1)
# Persist the event which should invalidate or prefill the
# `have_seen_event` cache so we don't return stale values.
persistence = self.hs.get_storage_controllers().persistence
self.get_success(
persistence.persist_event(
event,
event_context,
)
)
with LoggingContext(name="test") as ctx:
# Check `have_seen_event` again and we should see the updated fact
# that we have now seen the event after persisting it.
res = self.get_success(
self.store.have_seen_events(event.room_id, [event.event_id])
)
self.assertEqual(res, {event.event_id})
# That should result in a single db query to lookup
self.assertEqual(ctx.get_resource_usage().db_txn_count, 1)
def test_invalidate_cache_by_room_id(self):
"""
Test to make sure that all events associated with the given `(room_id,)`
are invalidated in the `have_seen_event` cache.
"""
with LoggingContext(name="test") as ctx:
# Prime the cache with some values
res = self.get_success(
self.store.have_seen_events(self.room_id, self.event_ids)
)
self.assertEqual(res, set(self.event_ids))
# That should result in a single db query to lookup
self.assertEqual(ctx.get_resource_usage().db_txn_count, 1)
# Clear the cache with any events associated with the `room_id`
self.store.have_seen_event.invalidate((self.room_id,))
with LoggingContext(name="test") as ctx:
res = self.get_success(
self.store.have_seen_events(self.room_id, self.event_ids)
)
self.assertEqual(res, set(self.event_ids))
# Since we cleared the cache, it should result in another db query to lookup
self.assertEqual(ctx.get_resource_usage().db_txn_count, 1)
class EventCacheTestCase(unittest.HomeserverTestCase):
"""Test that the various layers of event cache works."""

33
tests/util/caches/test_descriptors.py
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@ -13,7 +13,7 @@
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from typing import Set
from typing import Iterable, Set, Tuple
from unittest import mock
from twisted.internet import defer, reactor
@ -1008,3 +1008,34 @@ class CachedListDescriptorTestCase(unittest.TestCase):
obj.inner_context_was_finished, "Tried to restart a finished logcontext"
)
self.assertEqual(current_context(), SENTINEL_CONTEXT)
def test_num_args_mismatch(self):
"""
Make sure someone does not accidentally use @cachedList on a method with
a mismatch in the number args to the underlying single cache method.
"""
class Cls:
@descriptors.cached(tree=True)
def fn(self, room_id, event_id):
pass
# This is wrong ❌. `@cachedList` expects to be given the same number
# of arguments as the underlying cached function, just with one of
# the arguments being an iterable
@descriptors.cachedList(cached_method_name="fn", list_name="keys")
def list_fn(self, keys: Iterable[Tuple[str, str]]):
pass
# Corrected syntax ✅
#
# @cachedList(cached_method_name="fn", list_name="event_ids")
# async def list_fn(
# self, room_id: str, event_ids: Collection[str],
# )
obj = Cls()
# Make sure this raises an error about the arg mismatch
with self.assertRaises(Exception):
obj.list_fn([("foo", "bar")])