2 files changed, 11 insertions, 1 deletions
diff --git a/synapse/app/synchrotron.py b/synapse/app/synchrotron.py
index 07d3d047c6..dbaa48035d 100644
--- a/synapse/app/synchrotron.py
+++ b/synapse/app/synchrotron.py
@@ -242,6 +242,9 @@ class SynchrotronTyping(object):
         self._room_typing = {}
 
     def stream_positions(self):
+        # We must update this typing token from the response of the previous
+        # sync. In particular, the stream id may "reset" back to zero/a low
+        # value which we *must* use for the next replication request.
         return {"typing": self._latest_room_serial}
 
     def process_replication(self, result):
diff --git a/synapse/replication/resource.py b/synapse/replication/resource.py
index 857bc9795c..299e9419a4 100644
--- a/synapse/replication/resource.py
+++ b/synapse/replication/resource.py
@@ -274,11 +274,18 @@ class ReplicationResource(Resource):
 
     @defer.inlineCallbacks
     def typing(self, writer, current_token, request_streams):
-        current_position = current_token.presence
+        current_position = current_token.typing
 
         request_typing = request_streams.get("typing")
 
         if request_typing is not None:
+            # If they have a higher token than current max, we can assume that
+            # they had been talking to a previous instance of the master. Since
+            # we reset the token on restart, the best (but hacky) thing we can
+            # do is to simply resend down all the typing notifications.
+            if request_typing > current_position:
+                request_typing = 0
+
             typing_rows = yield self.typing_handler.get_all_typing_updates(
                 request_typing, current_position
             )