Faster room joins: avoid blocking when pulling events with missing prevs (#13355)

Avoid blocking on full state in `_resolve_state_at_missing_prevs` and
return a new flag indicating whether the resolved state is partial.
Thread that flag around so that it makes it into the event context.

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/synapse/storage/controllers/state.py b/synapse/storage/controllers/state.py
index e08f956e6e..20805c94fa 100644
--- a/synapse/storage/controllers/state.py
+++ b/synapse/storage/controllers/state.py
@@ -82,13 +82,15 @@ class StateStorageController:
         return state_group_delta.prev_group, state_group_delta.delta_ids
 
     async def get_state_groups_ids(
-        self, _room_id: str, event_ids: Collection[str]
+        self, _room_id: str, event_ids: Collection[str], await_full_state: bool = True
     ) -> Dict[int, MutableStateMap[str]]:
         """Get the event IDs of all the state for the state groups for the given events
 
         Args:
             _room_id: id of the room for these events
             event_ids: ids of the events
+            await_full_state: if `True`, will block if we do not yet have complete
+               state at these events.
 
         Returns:
             dict of state_group_id -> (dict of (type, state_key) -> event id)
@@ -100,7 +102,9 @@ class StateStorageController:
         if not event_ids:
             return {}
 
-        event_to_groups = await self.get_state_group_for_events(event_ids)
+        event_to_groups = await self.get_state_group_for_events(
+            event_ids, await_full_state=await_full_state
+        )
 
         groups = set(event_to_groups.values())
         group_to_state = await self.stores.state._get_state_for_groups(groups)