1 files changed, 8 insertions, 6 deletions
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index e54e2b322b..a8fe5cf4e2 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -376,9 +376,8 @@ class EventCreationHandler:
         self.notifier = hs.get_notifier()
         self.config = hs.config
         self.require_membership_for_aliases = hs.config.require_membership_for_aliases
-        self._is_event_writer = (
-            self.config.worker.writers.events == hs.get_instance_name()
-        )
+        self._events_shard_config = self.config.worker.events_shard_config
+        self._instance_name = hs.get_instance_name()
 
         self.room_invite_state_types = self.hs.config.room_invite_state_types
 
@@ -902,9 +901,10 @@ class EventCreationHandler:
 
         try:
             # If we're a worker we need to hit out to the master.
-            if not self._is_event_writer:
+            writer_instance = self._events_shard_config.get_instance(event.room_id)
+            if writer_instance != self._instance_name:
                 result = await self.send_event(
-                    instance_name=self.config.worker.writers.events,
+                    instance_name=writer_instance,
                     event_id=event.event_id,
                     store=self.store,
                     requester=requester,
@@ -972,8 +972,10 @@ class EventCreationHandler:
 
         This should only be run on the instance in charge of persisting events.
         """
-        assert self._is_event_writer
         assert self.storage.persistence is not None
+        assert self._events_shard_config.should_handle(
+            self._instance_name, event.room_id
+        )
 
         if ratelimit:
             # We check if this is a room admin redacting an event so that we