Adding thread prefix for ThreadPoolExecutor in Pub/Sub. (#4480)

Author: dhermes

google/cloud/pubsub_v1/subscriber/policy/thread.py

@@ -16,6 +16,7 @@
 
 from concurrent import futures
 import logging
+import sys
 import threading
 
 import grpc
@@ -106,7 +107,14 @@ def __init__(self, client, subscription, flow_control=types.FlowControl(),
 
         # Also maintain a request queue and an executor.
         if executor is None:
-            executor = futures.ThreadPoolExecutor(max_workers=10)
+            executor_kwargs = {}
+            if sys.version_info >= (3, 6):
+                executor_kwargs['thread_name_prefix'] = (
+                    'ThreadPoolExecutor-SubscriberPolicy')
+            executor = futures.ThreadPoolExecutor(
+                max_workers=10,
+                **executor_kwargs
+            )
         self._executor = executor
         _LOGGER.debug('Creating callback requests thread (not starting).')
         self._callback_requests = _helper_threads.QueueCallbackThread(