Ensure that cache_joined_hosts_for_event failing doesn't fail request

Author: erikjohnston

synapse/handlers/message.py

@@ -50,7 +50,7 @@
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.storage.state import StateFilter
 from synapse.types import Requester, RoomAlias, StreamToken, UserID, create_requester
-from synapse.util import json_decoder, json_encoder
+from synapse.util import json_decoder, json_encoder, log_failure
 from synapse.util.async_helpers import Linearizer, unwrapFirstError
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.metrics import measure_func
@@ -995,7 +995,7 @@ async def handle_new_client_event(
                     ),
                     run_in_background(
                         self.cache_joined_hosts_for_event, event, context
-                    ),
+                    ).addErrback(log_failure, "cache_joined_hosts_for_event failed"),
                 ],
                 consumeErrors=True,
             )