diff --git a/tests/handlers/test_federation.py b/tests/handlers/test_federation.py
index 745750b1d7..d00c69c229 100644
--- a/tests/handlers/test_federation.py
+++ b/tests/handlers/test_federation.py
@@ -19,7 +19,13 @@ from unittest.mock import Mock, patch
from twisted.test.proto_helpers import MemoryReactor
from synapse.api.constants import EventTypes
-from synapse.api.errors import AuthError, Codes, LimitExceededError, SynapseError
+from synapse.api.errors import (
+ AuthError,
+ Codes,
+ LimitExceededError,
+ NotFoundError,
+ SynapseError,
+)
from synapse.api.room_versions import RoomVersions
from synapse.events import EventBase, make_event_from_dict
from synapse.federation.federation_base import event_from_pdu_json
@@ -28,6 +34,7 @@ from synapse.logging.context import LoggingContext, run_in_background
from synapse.rest import admin
from synapse.rest.client import login, room
from synapse.server import HomeServer
+from synapse.storage.databases.main.events_worker import EventCacheEntry
from synapse.util import Clock
from synapse.util.stringutils import random_string
@@ -322,6 +329,102 @@ class FederationTestCase(unittest.FederatingHomeserverTestCase):
)
self.get_success(d)
+ def test_backfill_ignores_known_events(self) -> None:
+ """
+ Tests that events that we already know about are ignored when backfilling.
+ """
+ # Set up users
+ user_id = self.register_user("kermit", "test")
+ tok = self.login("kermit", "test")
+
+ other_server = "otherserver"
+ other_user = "@otheruser:" + other_server
+
+ # Create a room to backfill events into
+ room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+ room_version = self.get_success(self.store.get_room_version(room_id))
+
+ # Build an event to backfill
+ event = event_from_pdu_json(
+ {
+ "type": EventTypes.Message,
+ "content": {"body": "hello world", "msgtype": "m.text"},
+ "room_id": room_id,
+ "sender": other_user,
+ "depth": 32,
+ "prev_events": [],
+ "auth_events": [],
+ "origin_server_ts": self.clock.time_msec(),
+ },
+ room_version,
+ )
+
+ # Ensure the event is not already in the DB
+ self.get_failure(
+ self.store.get_event(event.event_id),
+ NotFoundError,
+ )
+
+ # Backfill the event and check that it has entered the DB.
+
+ # We mock out the FederationClient.backfill method, to pretend that a remote
+ # server has returned our fake event.
+ federation_client_backfill_mock = Mock(return_value=make_awaitable([event]))
+ self.hs.get_federation_client().backfill = federation_client_backfill_mock
+
+ # We also mock the persist method with a side effect of itself. This allows us
+ # to track when it has been called while preserving its function.
+ persist_events_and_notify_mock = Mock(
+ side_effect=self.hs.get_federation_event_handler().persist_events_and_notify
+ )
+ self.hs.get_federation_event_handler().persist_events_and_notify = (
+ persist_events_and_notify_mock
+ )
+
+ # Small side-tangent. We populate the event cache with the event, even though
+ # it is not yet in the DB. This is an invalid scenario that can currently occur
+ # due to not properly invalidating the event cache.
+ # See https://github.com/matrix-org/synapse/issues/13476.
+ #
+ # As a result, backfill should not rely on the event cache to check whether
+ # we already have an event in the DB.
+ # TODO: Remove this bit when the event cache is properly invalidated.
+ cache_entry = EventCacheEntry(
+ event=event,
+ redacted_event=None,
+ )
+ self.store._get_event_cache.set_local((event.event_id,), cache_entry)
+
+ # We now call FederationEventHandler.backfill (a separate method) to trigger
+ # a backfill request. It should receive the fake event.
+ self.get_success(
+ self.hs.get_federation_event_handler().backfill(
+ other_user,
+ room_id,
+ limit=10,
+ extremities=[],
+ )
+ )
+
+ # Check that our fake event was persisted.
+ persist_events_and_notify_mock.assert_called_once()
+ persist_events_and_notify_mock.reset_mock()
+
+ # Now we repeat the backfill, having the homeserver receive the fake event
+ # again.
+ self.get_success(
+ self.hs.get_federation_event_handler().backfill(
+ other_user,
+ room_id,
+ limit=10,
+ extremities=[],
+ ),
+ )
+
+ # This time, we expect no event persistence to have occurred, as we already
+ # have this event.
+ persist_events_and_notify_mock.assert_not_called()
+
@unittest.override_config(
{"rc_invites": {"per_user": {"per_second": 0.5, "burst_count": 3}}}
)
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