Implement clearing cache after deleting forward extremities

Also run linter.

Signed-off-by: Jason Robinson <jasonr@matrix.org>

1 files changed, 33 insertions, 8 deletions

diff --git a/synapse/storage/databases/main/events_forward_extremities.py b/synapse/storage/databases/main/events_forward_extremities.py
index cc684a94fe..6b8da52fee 100644
--- a/synapse/storage/databases/main/events_forward_extremities.py
+++ b/synapse/storage/databases/main/events_forward_extremities.py
@@ -1,15 +1,22 @@
-from typing import List, Dict
+import logging
+from typing import Dict, List
 
+from synapse.api.errors import SynapseError
 from synapse.storage._base import SQLBaseStore
 
+logger = logging.getLogger(__name__)
 
-class EventForwardExtremitiesStore(SQLBaseStore):
 
+class EventForwardExtremitiesStore(SQLBaseStore):
     async def delete_forward_extremities_for_room(self, room_id: str) -> int:
         """Delete any extra forward extremities for a room.
 
+        Invalidates the "get_latest_event_ids_in_room" cache if any forward
+        extremities were deleted.
+
         Returns count deleted.
         """
+
         def delete_forward_extremities_for_room_txn(txn):
             # First we need to get the event_id to not delete
             sql = (
@@ -27,9 +34,17 @@ class EventForwardExtremitiesStore(SQLBaseStore):
             )
             txn.execute(sql, (room_id,))
             rows = txn.fetchall()
-
-            # TODO: should this raise a SynapseError instead of better to blow?
-            event_id = rows[0][0]
+            try:
+                event_id = rows[0][0]
+                logger.debug(
+                    "Found event_id %s as the forward extremity to keep for room %s",
+                    event_id,
+                    room_id,
+                )
+            except KeyError:
+                msg = f"No forward extremity event found for room {room_id}"
+                logger.warning(msg)
+                raise SynapseError(400, msg)
 
             # Now delete the extra forward extremities
             sql = (
@@ -39,19 +54,29 @@ class EventForwardExtremitiesStore(SQLBaseStore):
                 "   AND room_id = ?"
             )
 
-            # TODO we should not commit yet
             txn.execute(sql, (event_id, room_id))
+            logger.info(
+                "Deleted %s extra forward extremities for room %s",
+                txn.rowcount,
+                room_id,
+            )
 
-            # TODO flush the cache then commit
+            if txn.rowcount > 0:
+                # Invalidate the cache
+                self._invalidate_cache_and_stream(
+                    txn, self.get_latest_event_ids_in_room, (room_id,),
+                )
 
             return txn.rowcount
 
         return await self.db_pool.runInteraction(
-            "delete_forward_extremities_for_room", delete_forward_extremities_for_room_txn,
+            "delete_forward_extremities_for_room",
+            delete_forward_extremities_for_room_txn,
         )
 
     async def get_forward_extremities_for_room(self, room_id: str) -> List[Dict]:
         """Get list of forward extremities for a room."""
+
         def get_forward_extremities_for_room_txn(txn):
             sql = (
                 "SELECT event_id, state_group FROM event_forward_extremities NATURAL JOIN event_to_state_groups "