Explicitly check for None rather than False

jeffwidman · jeffwidman · commit 411bc08f214b · 2017-10-06T14:44:04.000-07:00
If the group leader somehow gets in a state that it has an empty partition assignment, then `self._assignment_snapshot` will be `{}` which evaluates to `False`. So `self._subscription.mark_for_reassignment()` will never be triggered, even if `self._assignment_snapshot != self._metadata_snapshot`. Fixes the symptoms of dpkp#1237 although I suspect there's an additional bug in that case that triggers the condition of the the group leader getting an empty partition assignment.
diff --git a/kafka/coordinator/consumer.py b/kafka/coordinator/consumer.py
@@ -190,7 +190,7 @@ def _on_join_complete(self, generation, member_id, protocol,
         # if we were the assignor, then we need to make sure that there have
         # been no metadata updates since the rebalance begin. Otherwise, we
         # won't rebalance again until the next metadata change
-        if self._assignment_snapshot and self._assignment_snapshot != self._metadata_snapshot:
+        if self._assignment_snapshot is not None and self._assignment_snapshot != self._metadata_snapshot:
             self._subscription.mark_for_reassignment()
             return
 
