diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 978d3ee39f..55395457c3 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1384,6 +1384,7 @@ class TimestampLookupHandler:
self.store = hs.get_datastores().main
self.state_handler = hs.get_state_handler()
self.federation_client = hs.get_federation_client()
+ self.federation_event_handler = hs.get_federation_event_handler()
self._storage_controllers = hs.get_storage_controllers()
async def get_event_for_timestamp(
@@ -1479,38 +1480,68 @@ class TimestampLookupHandler:
remote_response,
)
- # TODO: Do we want to persist this as an extremity?
- # TODO: I think ideally, we would try to backfill from
- # this event and run this whole
- # `get_event_for_timestamp` function again to make sure
- # they didn't give us an event from their gappy history.
remote_event_id = remote_response.event_id
- origin_server_ts = remote_response.origin_server_ts
+ remote_origin_server_ts = remote_response.origin_server_ts
+
+ # Backfill this event so we can get a pagination token for
+ # it with `/context` and paginate `/messages` from this
+ # point.
+ #
+ # TODO: The requested timestamp may lie in a part of the
+ # event graph that the remote server *also* didn't have,
+ # in which case they will have returned another event
+ # which may be nowhere near the requested timestamp. In
+ # the future, we may need to reconcile that gap and ask
+ # other homeservers, and/or extend `/timestamp_to_event`
+ # to return events on *both* sides of the timestamp to
+ # help reconcile the gap faster.
+ remote_event = (
+ await self.federation_event_handler.backfill_event_id(
+ domain, room_id, remote_event_id
+ )
+ )
+
+ # XXX: When we see that the remote server is not trustworthy,
+ # maybe we should not ask them first in the future.
+ if remote_origin_server_ts != remote_event.origin_server_ts:
+ logger.info(
+ "get_event_for_timestamp: Remote server (%s) claimed that remote_event_id=%s occured at remote_origin_server_ts=%s but that isn't true (actually occured at %s). Their claims are dubious and we should consider not trusting them.",
+ domain,
+ remote_event_id,
+ remote_origin_server_ts,
+ remote_event.origin_server_ts,
+ )
# Only return the remote event if it's closer than the local event
if not local_event or (
- abs(origin_server_ts - timestamp)
+ abs(remote_event.origin_server_ts - timestamp)
< abs(local_event.origin_server_ts - timestamp)
):
- return remote_event_id, origin_server_ts
+ logger.info(
+ "get_event_for_timestamp: returning remote_event_id=%s (%s) since it's closer to timestamp=%s than local_event=%s (%s)",
+ remote_event_id,
+ remote_event.origin_server_ts,
+ timestamp,
+ local_event.event_id if local_event else None,
+ local_event.origin_server_ts if local_event else None,
+ )
+ return remote_event_id, remote_origin_server_ts
except (HttpResponseException, InvalidResponseError) as ex:
# Let's not put a high priority on some other homeserver
# failing to respond or giving a random response
logger.debug(
- "Failed to fetch /timestamp_to_event from %s because of exception(%s) %s args=%s",
+ "get_event_for_timestamp: Failed to fetch /timestamp_to_event from %s because of exception(%s) %s args=%s",
domain,
type(ex).__name__,
ex,
ex.args,
)
- except Exception as ex:
+ except Exception:
# But we do want to see some exceptions in our code
logger.warning(
- "Failed to fetch /timestamp_to_event from %s because of exception(%s) %s args=%s",
+ "get_event_for_timestamp: Failed to fetch /timestamp_to_event from %s because of exception",
domain,
- type(ex).__name__,
- ex,
- ex.args,
+ exc_info=True,
)
# To appease mypy, we have to add both of these conditions to check for
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