Fix pending completion IndexError bug caused by multiple threads (dpkp#1372)

dpkp · web-flow · commit 41aa0342f8bf · 2018-02-08T11:59:54.000-08:00
diff --git a/kafka/client_async.py b/kafka/client_async.py
@@ -665,8 +665,14 @@ def in_flight_request_count(self, node_id=None):
 
     def _fire_pending_completed_requests(self):
         responses = []
-        while self._pending_completion:
-            response, future = self._pending_completion.popleft()
+        while True:
+            try:
+                # We rely on deque.popleft remaining threadsafe
+                # to allow both the heartbeat thread and the main thread
+                # to process responses
+                response, future = self._pending_completion.popleft()
+            except IndexError:
+                break
             future.success(response)
             responses.append(response)
         return responses
