Log some bits about event creation (#4121)

I found these helpful in debugging my room upgrade tests.

changelog.d/4121.misc

@@ -0,0 +1 @@
+Log some bits about room creation

synapse/handlers/message.py

@@ -427,6 +427,9 @@ class EventCreationHandler(object):
 
         if event.is_state():
             prev_state = yield self.deduplicate_state_event(event, context)
+            logger.info(
+                "Not bothering to persist duplicate state event %s", event.event_id,
+            )
             if prev_state is not None:
                 defer.returnValue(prev_state)
 

synapse/handlers/room.py

@@ -104,6 +104,8 @@ class RoomCreationHandler(BaseHandler):
                 creator_id=user_id, is_public=r["is_public"],
             )
 
+            logger.info("Creating new room %s to replace %s", new_room_id, old_room_id)
+
             # we create and auth the tombstone event before properly creating the new
             # room, to check our user has perms in the old room.
             tombstone_event, tombstone_context = (
@@ -522,6 +524,7 @@ class RoomCreationHandler(BaseHandler):
         @defer.inlineCallbacks
         def send(etype, content, **kwargs):
             event = create(etype, content, **kwargs)
+            logger.info("Sending %s in new room", etype)
             yield self.event_creation_handler.create_and_send_nonmember_event(
                 creator,
                 event,
@@ -544,6 +547,7 @@ class RoomCreationHandler(BaseHandler):
             content=creation_content,
         )
 
+        logger.info("Sending %s in new room", EventTypes.Member)
         yield self.room_member_handler.update_membership(
             creator,
             creator.user,