diff options
Diffstat (limited to 'synapse/handlers')
| -rw-r--r-- | synapse/handlers/federation.py | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index f80486102a..72b63d64d0 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -858,6 +858,52 @@ class FederationHandler(BaseHandler): logger.debug("Not backfilling as no extremeties found.") return + # We only want to paginate if we can actually see the events we'll get, + # as otherwise we'll just spend a lot of resources to get redacted + # events. + # + # We do this by filtering all the backwards extremities and seeing if + # any remain. Given we don't have the extremity events themselves, we + # need to actually check the events that reference them. + # + # *Note*: the spec wants us to keep backfilling until we reach the start + # of the room in case we are allowed to see some of the history. However + # in practice that causes more issues than its worth, as a) its + # relatively rare for there to be any visible history and b) even when + # there is its often sufficiently long ago that clients would stop + # attempting to paginate before backfill reached the visible history. + # + # TODO: If we do do a backfill then we should filter the backwards + # extremities to only include those that point to visible portions of + # history. + # + # TODO: Correctly handle the case where we are allowed to see the + # forward event but not the backward extremity, e.g. in the case of + # initial join of the server where we are allowed to see the join + # event but not anything before it. This would require looking at the + # state *before* the event, ignoring the special casing certain event + # types have. + + forward_events = yield self.store.get_successor_events( + list(extremities), + ) + + extremities_events = yield self.store.get_events( + forward_events, + check_redacted=False, + get_prev_content=False, + ) + + # We set `check_history_visibility_only` as we might otherwise get false + # positives from users having been erased. + filtered_extremities = yield filter_events_for_server( + self.store, self.server_name, list(extremities_events.values()), + redact=False, check_history_visibility_only=True, + ) + + if not filtered_extremities: + defer.returnValue(False) + # Check if we reached a point where we should start backfilling. sorted_extremeties_tuple = sorted( extremities.items(), |