Avoid shutting down of a passed executor

For the case where an executor is being provided we
should not shutdown the executor on-behalf of the
provider since they would likely expect that they
can still use the executor elsewhere. If the executor
is shutdown then further usage is not possible.

Change-Id: Ia83d8c2f1df06200e32e9b0c7340f32e74fd5d85

taskflow/engines/worker_based/server.py

@@ -173,4 +173,3 @@ class Server(object):
     def stop(self):
         """Stop processing incoming requests."""
         self._proxy.stop()
-        self._executor.shutdown()

taskflow/engines/worker_based/worker.py

@@ -71,6 +71,7 @@ class Worker(object):
     def __init__(self, exchange, topic, tasks, executor=None, **kwargs):
         self._topic = topic
         self._executor = executor
+        self._owns_executor = False
         self._threads_count = -1
         if self._executor is None:
             if 'threads_count' in kwargs:
@@ -80,6 +81,7 @@ class Worker(object):
             else:
                 self._threads_count = tu.get_optimal_thread_count()
             self._executor = futures.ThreadPoolExecutor(self._threads_count)
+            self._owns_executor = True
         self._endpoints = self._derive_endpoints(tasks)
         self._server = server.Server(topic, exchange, self._executor,
                                      self._endpoints, **kwargs)
@@ -137,3 +139,5 @@ class Worker(object):
     def stop(self):
         """Stop worker."""
         self._server.stop()
+        if self._owns_executor:
+            self._executor.shutdown()

taskflow/tests/unit/worker_based/test_server.py

@@ -371,7 +371,6 @@ class TestServer(test.MockTestCase):
 
         # check calls
         master_mock_calls = [
-            mock.call.proxy.stop(),
-            mock.call.executor.shutdown()
+            mock.call.proxy.stop()
         ]
         self.assertEqual(self.master_mock.mock_calls, master_mock_calls)

taskflow/tests/unit/worker_based/test_worker.py

@@ -119,7 +119,8 @@ class TestWorker(test.MockTestCase):
         self.worker(reset_master_mock=True).stop()
 
         master_mock_calls = [
-            mock.call.server.stop()
+            mock.call.server.stop(),
+            mock.call.executor.shutdown()
         ]
         self.assertEqual(self.master_mock.mock_calls, master_mock_calls)