Add some logging

synapse/handlers/federation.py

@@ -247,6 +247,11 @@ class FederationHandler(BaseHandler):
             if set(e_id for e_id, _ in ev.prev_events) - event_ids
         ]
 
+        logger.info(
+            "backfill: Got %d events with %d edges",
+            len(events), len(edges),
+        )
+
         # For each edge get the current state.
 
         auth_events = {}