Bound ephemeral events by key

changelog.d/12544.bugfix

@@ -0,0 +1 @@
+Bound read receipts being sent to app services to avoid runaway memory in AS worker. Contributed by Brad & Nick @ Beeper.

synapse/handlers/appservice.py

@@ -416,7 +416,7 @@ async def _handle_typing(
         return typing
 
     async def _handle_receipts(
-        self, service: ApplicationService, new_token: Optional[int]
+        self, service: ApplicationService, new_token: int
     ) -> List[JsonDict]:
         """
         Return the latest read receipts that the given application service should receive.
@@ -447,7 +447,7 @@ async def _handle_receipts(
 
         receipts_source = self.event_sources.sources.receipt
         receipts, _ = await receipts_source.get_new_events_as(
-            service=service, from_key=from_key
+            service=service, from_key=from_key, to_key=new_token
         )
         return receipts
 

synapse/handlers/receipts.py

@@ -239,13 +239,14 @@ async def get_new_events(
         return events, to_key
 
     async def get_new_events_as(
-        self, from_key: int, service: ApplicationService
+        self, from_key: int, to_key: int, service: ApplicationService
     ) -> Tuple[List[JsonDict], int]:
         """Returns a set of new read receipt events that an appservice
         may be interested in.
 
         Args:
             from_key: the stream position at which events should be fetched from
+            to_key: the stream position up to which events should be fetched to
             service: The appservice which may be interested
 
         Returns:
@@ -255,7 +256,6 @@ async def get_new_events_as(
                 * The current read receipt stream token.
         """
         from_key = int(from_key)
-        to_key = self.get_current_key()
 
         if from_key == to_key:
             return [], to_key