Cache event ID to auth event IDs lookups (#8752)

This should hopefully speed up `get_auth_chain_difference` a bit in the case of repeated state res on the same rooms.

`get_auth_chain_difference` does a breadth first walk of the auth graphs by repeatedly looking up events' auth events. Different state resolutions on the same room will end up doing a lot of the same event to auth events lookups, so by caching them we should speed things up in cases of repeated state resolutions on the same room.
This commit is contained in:
Erik Johnston 2020-11-13 11:29:18 +00:00 committed by GitHub
parent c2d4467cd4
commit 4cb00d297f
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2 changed files with 71 additions and 12 deletions

1
changelog.d/8752.misc Normal file
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@ -0,0 +1 @@
Speed up repeated state resolutions on the same room by caching event ID to auth event ID lookups.

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@ -26,6 +26,7 @@ from synapse.storage.databases.main.events_worker import EventsWorkerStore
from synapse.storage.databases.main.signatures import SignatureWorkerStore
from synapse.types import Collection
from synapse.util.caches.descriptors import cached
from synapse.util.caches.lrucache import LruCache
from synapse.util.iterutils import batch_iter
logger = logging.getLogger(__name__)
@ -40,6 +41,11 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
self._delete_old_forward_extrem_cache, 60 * 60 * 1000
)
# Cache of event ID to list of auth event IDs and their depths.
self._event_auth_cache = LruCache(
500000, "_event_auth_cache", size_callback=len
) # type: LruCache[str, List[Tuple[str, int]]]
async def get_auth_chain(
self, event_ids: Collection[str], include_given: bool = False
) -> List[EventBase]:
@ -84,17 +90,45 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
else:
results = set()
base_sql = "SELECT DISTINCT auth_id FROM event_auth WHERE "
# We pull out the depth simply so that we can populate the
# `_event_auth_cache` cache.
base_sql = """
SELECT a.event_id, auth_id, depth
FROM event_auth AS a
INNER JOIN events AS e ON (e.event_id = a.auth_id)
WHERE
"""
front = set(event_ids)
while front:
new_front = set()
for chunk in batch_iter(front, 100):
# Pull the auth events either from the cache or DB.
to_fetch = [] # Event IDs to fetch from DB # type: List[str]
for event_id in chunk:
res = self._event_auth_cache.get(event_id)
if res is None:
to_fetch.append(event_id)
else:
new_front.update(auth_id for auth_id, depth in res)
if to_fetch:
clause, args = make_in_list_sql_clause(
txn.database_engine, "event_id", chunk
txn.database_engine, "a.event_id", to_fetch
)
txn.execute(base_sql + clause, args)
new_front.update(r[0] for r in txn)
# Note we need to batch up the results by event ID before
# adding to the cache.
to_cache = {}
for event_id, auth_event_id, auth_event_depth in txn:
to_cache.setdefault(event_id, []).append(
(auth_event_id, auth_event_depth)
)
new_front.add(auth_event_id)
for event_id, auth_events in to_cache.items():
self._event_auth_cache.set(event_id, auth_events)
new_front -= results
@ -213,14 +247,38 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
break
# Fetch the auth events and their depths of the N last events we're
# currently walking
# currently walking, either from cache or DB.
search, chunk = search[:-100], search[-100:]
found = [] # Results found # type: List[Tuple[str, str, int]]
to_fetch = [] # Event IDs to fetch from DB # type: List[str]
for _, event_id in chunk:
res = self._event_auth_cache.get(event_id)
if res is None:
to_fetch.append(event_id)
else:
found.extend((event_id, auth_id, depth) for auth_id, depth in res)
if to_fetch:
clause, args = make_in_list_sql_clause(
txn.database_engine, "a.event_id", [e_id for _, e_id in chunk]
txn.database_engine, "a.event_id", to_fetch
)
txn.execute(base_sql + clause, args)
# We parse the results and add the to the `found` set and the
# cache (note we need to batch up the results by event ID before
# adding to the cache).
to_cache = {}
for event_id, auth_event_id, auth_event_depth in txn:
to_cache.setdefault(event_id, []).append(
(auth_event_id, auth_event_depth)
)
found.append((event_id, auth_event_id, auth_event_depth))
for event_id, auth_events in to_cache.items():
self._event_auth_cache.set(event_id, auth_events)
for event_id, auth_event_id, auth_event_depth in found:
event_to_auth_events.setdefault(event_id, set()).add(auth_event_id)
sets = event_to_missing_sets.get(auth_event_id)