Fixup pusher pool notifications (#8287)

`pusher_pool.on_new_notifications` expected a min and max stream ID, however that was not what we were passing in. Instead, let's just pass it the current max stream ID and have it track the last stream ID it got passed.

I believe that it mostly worked as we called the function for every event. However, it would break for events that got persisted out of order, i.e, that were persisted but the max stream ID wasn't incremented as not all preceding events had finished persisting, and push for that event would be delayed until another event got pushed to the effected users.

changelog.d/8287.bugfix

@@ -0,0 +1 @@
+Fix edge case where push could get delayed for a user until a later event was pushed.

synapse/handlers/federation.py

@@ -2970,7 +2970,7 @@ async def _notify_persisted_event(
             event, event_stream_id, max_stream_id, extra_users=extra_users
         )
 
-        await self.pusher_pool.on_new_notifications(event_stream_id, max_stream_id)
+        await self.pusher_pool.on_new_notifications(max_stream_id)
 
     async def _clean_room_for_join(self, room_id: str) -> None:
         """Called to clean up any data in DB for a given room, ready for the

synapse/handlers/message.py

@@ -1145,7 +1145,7 @@ def is_inviter_member_event(e):
             # If there's an expiry timestamp on the event, schedule its expiry.
             self._message_handler.maybe_schedule_expiry(event)
 
-        await self.pusher_pool.on_new_notifications(event_stream_id, max_stream_id)
+        await self.pusher_pool.on_new_notifications(max_stream_id)
 
         def _notify():
             try:

synapse/push/emailpusher.py

@@ -91,7 +91,7 @@ def on_stop(self):
                 pass
             self.timed_call = None
 
-    def on_new_notifications(self, min_stream_ordering, max_stream_ordering):
+    def on_new_notifications(self, max_stream_ordering):
         if self.max_stream_ordering:
             self.max_stream_ordering = max(
                 max_stream_ordering, self.max_stream_ordering

synapse/push/httppusher.py

@@ -114,7 +114,7 @@ def on_started(self, should_check_for_notifs):
         if should_check_for_notifs:
             self._start_processing()
 
-    def on_new_notifications(self, min_stream_ordering, max_stream_ordering):
+    def on_new_notifications(self, max_stream_ordering):
         self.max_stream_ordering = max(
             max_stream_ordering, self.max_stream_ordering or 0
         )

synapse/push/pusherpool.py

@@ -64,6 +64,12 @@ def __init__(self, hs: "HomeServer"):
         self._pusher_shard_config = hs.config.push.pusher_shard_config
         self._instance_name = hs.get_instance_name()
 
+        # Record the last stream ID that we were poked about so we can get
+        # changes since then. We set this to the current max stream ID on
+        # startup as every individual pusher will have checked for changes on
+        # startup.
+        self._last_room_stream_id_seen = self.store.get_room_max_stream_ordering()
+
         # map from user id to app_id:pushkey to pusher
         self.pushers = {}  # type: Dict[str, Dict[str, Union[HttpPusher, EmailPusher]]]
 
@@ -178,20 +184,27 @@ async def remove_pushers_by_access_token(self, user_id, access_tokens):
                 )
                 await self.remove_pusher(p["app_id"], p["pushkey"], p["user_name"])
 
-    async def on_new_notifications(self, min_stream_id, max_stream_id):
+    async def on_new_notifications(self, max_stream_id):
         if not self.pushers:
             # nothing to do here.
             return
 
+        if max_stream_id < self._last_room_stream_id_seen:
+            # Nothing to do
+            return
+
+        prev_stream_id = self._last_room_stream_id_seen
+        self._last_room_stream_id_seen = max_stream_id
+
         try:
             users_affected = await self.store.get_push_action_users_in_range(
-                min_stream_id, max_stream_id
+                prev_stream_id, max_stream_id
             )
 
             for u in users_affected:
                 if u in self.pushers:
                     for p in self.pushers[u].values():
-                        p.on_new_notifications(min_stream_id, max_stream_id)
+                        p.on_new_notifications(max_stream_id)
 
         except Exception:
             logger.exception("Exception in pusher on_new_notifications")

synapse/replication/tcp/client.py

@@ -154,7 +154,8 @@ async def on_rdata(
                 max_token = self.store.get_room_max_stream_ordering()
                 self.notifier.on_new_room_event(event, token, max_token, extra_users)
 
-            await self.pusher_pool.on_new_notifications(token, token)
+            max_token = self.store.get_room_max_stream_ordering()
+            await self.pusher_pool.on_new_notifications(max_token)
 
         # Notify any waiting deferreds. The list is ordered by position so we
         # just iterate through the list until we reach a position that is

tests/handlers/test_typing.py

@@ -80,6 +80,7 @@ def make_homeserver(self, reactor, clock):
                 "get_user_directory_stream_pos",
                 "get_current_state_deltas",
                 "get_device_updates_by_remote",
+                "get_room_max_stream_ordering",
             ]
         )