Ensure local invited & knocking users leave before purge. (#16559)

This is mostly useful for federated rooms where some users
would get stuck in the invite or knock state when the room
was purged from their homeserver.

2 files changed, 20 insertions, 3 deletions

diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 97c9f01245..6d680b0795 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1939,9 +1939,10 @@ class RoomShutdownHandler:
         else:
             logger.info("Shutting down room %r", room_id)
 
-        users = await self.store.get_users_in_room(room_id)
-        for user_id in users:
-            if not self.hs.is_mine_id(user_id):
+        users = await self.store.get_local_users_related_to_room(room_id)
+        for user_id, membership in users:
+            # If the user is not in the room (or is banned), nothing to do.
+            if membership not in (Membership.JOIN, Membership.INVITE, Membership.KNOCK):
                 continue
 
             logger.info("Kicking %r from %r...", user_id, room_id)
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 67e149b586..1ed7f2d0ef 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -482,6 +482,22 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
             desc="get_local_users_in_room",
         )
 
+    async def get_local_users_related_to_room(
+        self, room_id: str
+    ) -> List[Tuple[str, str]]:
+        """
+        Retrieves a list of the current roommembers who are local to the server and their membership status.
+        """
+        return cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="local_current_membership",
+                keyvalues={"room_id": room_id},
+                retcols=("user_id", "membership"),
+                desc="get_local_users_in_room",
+            ),
+        )
+
     async def check_local_user_in_room(self, user_id: str, room_id: str) -> bool:
         """
         Check whether a given local user is currently joined to the given room.