Ignore AS users when fetching push rules

By ignoring AS users early on when fetching push rules for a room we can
avoid needlessly hitting the DB and filling up the caches.

synapse/storage/appservice.py

@@ -39,6 +39,14 @@ class ApplicationServiceStore(SQLBaseStore):
     def get_app_services(self):
         return self.services_cache
 
+    def get_if_app_services_interested_in_user(self, user_id):
+        """Check if the user is one associated with an app service
+        """
+        for service in self.services_cache:
+            if service.is_interested_in_user(user_id):
+                return True
+        return False
+
     def get_app_service_by_user_id(self, user_id):
         """Retrieve an application service from their user ID.
 

synapse/storage/push_rule.py

@@ -156,12 +156,20 @@ class PushRuleStore(SQLBaseStore):
             event=event,
         )
 
-        local_users_in_room = set(u for u in users_in_room if self.hs.is_mine_id(u))
+        # We ignore app service users for now. This is so that we don't fill
+        # up the `get_if_users_have_pushers` cache with AS entries that we
+        # know don't have pushers, nor even read receipts.
+        local_users_in_room = set(
+            u for u in users_in_room
+            if self.hs.is_mine_id(u)
+            and not self.get_if_app_services_interested_in_user(u)
+        )
 
         # users in the room who have pushers need to get push rules run because
         # that's how their pushers work
         if_users_with_pushers = yield self.get_if_users_have_pushers(
-            local_users_in_room, on_invalidate=cache_context.invalidate,
+            local_users_in_room,
+            on_invalidate=cache_context.invalidate,
         )
         user_ids = set(
             uid for uid, have_pusher in if_users_with_pushers.items() if have_pusher