Fix the negative sleep value in graceful_shutdown()

This fixes the following comment to avoid having the
negative sleep value in manager graceful_shutdown()

- https://review.opendev.org/c/openstack/nova/+/975586/comment/d5e3a603_0c746704/

Change-Id: I07a994bd05ac1e7f734f2a2144327bd2559c1416
Signed-off-by: Ghanshyam Maan <gmaan.os14@gmail.com>

nova/compute/manager.py

@@ -1827,7 +1827,7 @@ class ComputeManager(manager.Manager):
                         'killed before the manager finishes waiting.',
                         CONF.manager_shutdown_timeout,
                         CONF.graceful_shutdown_timeout)
-            sleep_time = CONF.graceful_shutdown_timeout - 10
+            sleep_time = max(0, CONF.graceful_shutdown_timeout - 10)
         else:
             sleep_time = CONF.manager_shutdown_timeout
         LOG.debug('Compute service manager is waiting for %s seconds to '

nova/conductor/manager.py

@@ -218,7 +218,7 @@ class ConductorManager(manager.Manager):
                         'killed before the manager finishes waiting.',
                         CONF.manager_shutdown_timeout,
                         CONF.graceful_shutdown_timeout)
-            sleep_time = CONF.graceful_shutdown_timeout - 10
+            sleep_time = max(0, CONF.graceful_shutdown_timeout - 10)
         else:
             sleep_time = CONF.manager_shutdown_timeout
         LOG.debug('Conductor service manager is waiting for %s seconds to '

nova/scheduler/manager.py

@@ -172,7 +172,7 @@ class SchedulerManager(manager.Manager):
                         'killed before the manager finishes waiting.',
                         CONF.manager_shutdown_timeout,
                         CONF.graceful_shutdown_timeout)
-            sleep_time = CONF.graceful_shutdown_timeout - 10
+            sleep_time = max(0, CONF.graceful_shutdown_timeout - 10)
         else:
             sleep_time = CONF.manager_shutdown_timeout
         LOG.debug('Scheduler service manager is waiting for %s seconds to '

nova/tests/unit/compute/test_compute_mgr.py

@@ -8005,6 +8005,16 @@ class ComputeManagerUnitTestCase(test.NoDBTestCase,
         mock_sleep.assert_called_once_with(20)
         mock_cleanup.assert_called_once_with()
 
+    @mock.patch('time.sleep')
+    @mock.patch('nova.compute.manager.ComputeManager.cleanup_host')
+    def test_graceful_shutdown_no_negative_sleep_time(
+            self, mock_cleanup, mock_sleep):
+        # If sleep time end up with negative value, fallback to slep(0)
+        self.flags(manager_shutdown_timeout=50, graceful_shutdown_timeout=5)
+        self.compute.graceful_shutdown()
+        mock_sleep.assert_called_once_with(0)
+        mock_cleanup.assert_called_once_with()
+
     @mock.patch('nova.objects.BlockDeviceMappingList.get_by_instance_uuid')
     @mock.patch('nova.compute.manager.ComputeManager._delete_instance')
     def test_terminate_instance_no_bdm_volume_id(self, mock_delete_instance,

nova/tests/unit/conductor/test_conductor.py

@@ -320,6 +320,13 @@ class ConductorTestCase(_BaseTestCase, test.TestCase):
         mock_log.warning.assert_called_once()
         mock_sleep.assert_called_once_with(20)
 
+    @mock.patch('time.sleep')
+    def test_graceful_shutdown_no_negative_sleep_time(self, mock_sleep):
+        # If sleep time end up with negative value, fallback to slep(0)
+        self.flags(manager_shutdown_timeout=50, graceful_shutdown_timeout=5)
+        self.conductor.graceful_shutdown()
+        mock_sleep.assert_called_once_with(0)
+
     def test_provider_fw_rule_get_all(self):
         result = self.conductor.provider_fw_rule_get_all(self.context)
         self.assertEqual([], result)

nova/tests/unit/scheduler/test_manager.py

@@ -1678,6 +1678,13 @@ class SchedulerManagerTestCase(test.NoDBTestCase):
         mock_log.warning.assert_called_once()
         mock_sleep.assert_called_once_with(20)
 
+    @mock.patch('time.sleep')
+    def test_graceful_shutdown_no_negative_sleep_time(self, mock_sleep):
+        # If sleep time end up with negative value, fallback to slep(0)
+        self.flags(manager_shutdown_timeout=50, graceful_shutdown_timeout=5)
+        self.manager.graceful_shutdown()
+        mock_sleep.assert_called_once_with(0)
+
     @mock.patch('nova.objects.service.ServiceList.get_by_binary')
     @mock.patch('nova.objects.host_mapping.discover_hosts')
     def test_discover_hosts(self, mock_discover, mock_get_by_binary):