Fix race condition where pending Ack IDs can be modified by another thread. (#5929)

theacodes · web-flow · commit f074335bf086 · 2018-09-12T15:32:34.000-07:00
diff --git a/pubsub/google/cloud/pubsub_v1/subscriber/_protocol/streaming_pull_manager.py b/pubsub/google/cloud/pubsub_v1/subscriber/_protocol/streaming_pull_manager.py
@@ -379,7 +379,9 @@ def _get_initial_request(self):
         # Any ack IDs that are under lease management need to have their
         # deadline extended immediately.
         if self._leaser is not None:
-            lease_ids = self._leaser.ack_ids
+            # Explicitly copy the list, as it could be modified by another
+            # thread.
+            lease_ids = list(self._leaser.ack_ids)
         else:
             lease_ids = []
 
