Make create task as non-blocking

Currently, the create task api is blocking and waits until the task
is complete to return a 201 but that too with a Pending status.

The patch runs the task executor in an eventlet thread.

Closes-Bug: #1459051

Change-Id: I94f932afb5b754d9bcfa7bbbd1c450bdef7f28ef

glance/api/v2/tasks.py

@@ -25,6 +25,7 @@ import six
 import six.moves.urllib.parse as urlparse
 import webob.exc
 
+from glance.api import common
 from glance.api import policy
 from glance.common import exception
 from glance.common import utils
@@ -67,7 +68,8 @@ class TasksController(object):
                                              task_input=task['input'])
             task_repo.add(new_task)
             task_executor = executor_factory.new_task_executor(req.context)
-            new_task.run(task_executor)
+            pool = common.get_thread_pool("tasks_eventlet_pool")
+            pool.spawn_n(new_task.run, task_executor)
         except exception.Forbidden as e:
             msg = (_LW("Forbidden to create task. Reason: %(reason)s")
                    % {'reason': utils.exception_to_str(e)})

glance/tests/integration/v2/test_tasks_api.py

@@ -146,6 +146,10 @@ class TestTasksApi(base.ApiTest):
                                               headers=minimal_task_headers())
         self.assertEqual(200, response.status)
 
+        # NOTE(sabari): wait for all task executions to finish before checking
+        # task status.
+        self._wait_on_task_execution()
+
         # 4. GET /tasks
         # Get all tasks (not deleted)
         path = "/v2/tasks"
@@ -169,10 +173,6 @@ class TestTasksApi(base.ApiTest):
         self.assertIsNotNone(task['created_at'])
         self.assertIsNotNone(task['updated_at'])
 
-        # NOTE(nikhil): wait for all task executions to finish before exiting
-        # else there is a risk of running into deadlock
-        self._wait_on_task_execution()
-
     def test_task_schema_api(self):
         # 0. GET /schemas/task
         # Verify schema for task