Reduce amount of state we pull out when attempting to send catchup PDUs. (#12963)

* Don't pull out state for catchup

* Newsfile

* Merge newsfile

Author: erikjohnston

changelog.d/12963.misc

@@ -0,0 +1 @@
+Reduce the amount of state we pull from the DB.

synapse/federation/sender/per_destination_queue.py

@@ -37,6 +37,7 @@
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.types import ReadReceipt
 from synapse.util.retryutils import NotRetryingDestination, get_retry_limiter
+from synapse.visibility import filter_events_for_server
 
 if TYPE_CHECKING:
     import synapse.server
@@ -77,6 +78,7 @@ def __init__(
     ):
         self._server_name = hs.hostname
         self._clock = hs.get_clock()
+        self._storage_controllers = hs.get_storage_controllers()
         self._store = hs.get_datastores().main
         self._transaction_manager = transaction_manager
         self._instance_name = hs.get_instance_name()
@@ -442,6 +444,12 @@ async def _catch_up_transmission_loop(self) -> None:
                     "This should not happen." % event_ids
                 )
 
+            logger.info(
+                "Catching up destination %s with %d PDUs",
+                self._destination,
+                len(catchup_pdus),
+            )
+
             # We send transactions with events from one room only, as its likely
             # that the remote will have to do additional processing, which may
             # take some time. It's better to give it small amounts of work
@@ -487,19 +495,20 @@ async def _catch_up_transmission_loop(self) -> None:
                         ):
                             continue
 
-                        # Filter out events where the server is not in the room,
-                        # e.g. it may have left/been kicked. *Ideally* we'd pull
-                        # out the kick and send that, but it's a rare edge case
-                        # so we don't bother for now (the server that sent the
-                        # kick should send it out if its online).
-                        hosts = await self._state.get_hosts_in_room_at_events(
-                            p.room_id, [p.event_id]
-                        )
-                        if self._destination not in hosts:
-                            continue
-
                         new_pdus.append(p)
 
+                    # Filter out events where the server is not in the room,
+                    # e.g. it may have left/been kicked. *Ideally* we'd pull
+                    # out the kick and send that, but it's a rare edge case
+                    # so we don't bother for now (the server that sent the
+                    # kick should send it out if its online).
+                    new_pdus = await filter_events_for_server(
+                        self._storage_controllers,
+                        self._destination,
+                        new_pdus,
+                        redact=False,
+                    )
+
                     # If we've filtered out all the extremities, fall back to
                     # sending the original event. This should ensure that the
                     # server gets at least some of missed events (especially if