fix VM power state to be NOSTATE when instance not found

* nova/compute/manager.py (_sync_power_states): Revert what looks
like an inadvertent change that was part of commit 95e77703.
Also log the condition.

Fixes bug: 1085771
Change-Id: Ic6eeb9207323f05b93f0b613bd1bddd681ad8ce5

nova/compute/manager.py

@@ -3371,7 +3371,7 @@ class ComputeManager(manager.SchedulerDependentManager):
                 vm_instance = self.driver.get_info(db_instance)
                 vm_power_state = vm_instance['state']
             except exception.InstanceNotFound:
-                vm_power_state = power_state.SHUTDOWN
+                vm_power_state = power_state.NOSTATE
             # Note(maoy): the above get_info call might take a long time,
             # for example, because of a broken libvirt driver.
             # We re-query the DB to get the latest instance info to minimize
@@ -3458,6 +3458,12 @@ class ComputeManager(manager.SchedulerDependentManager):
                     # instrumentation is done. See bug 1097806 for details.
                     LOG.warn(_("Instance is paused unexpectedly. Ignore."),
                              instance=db_instance)
+                elif vm_power_state == power_state.NOSTATE:
+                    # Occasionally, depending on the status of the hypervisor,
+                    # which could be restarting for example, an instance may
+                    # not be found.  Therefore just log the condidtion.
+                    LOG.warn(_("Instance is unexpectedly not found. Ignore."),
+                             instance=db_instance)
             elif vm_state == vm_states.STOPPED:
                 if vm_power_state not in (power_state.NOSTATE,
                                           power_state.SHUTDOWN,

nova/tests/compute/test_compute.py

@@ -2776,7 +2776,7 @@ class ComputeTestCase(BaseTestCase):
         instances = db.instance_get_all(self.context)
         LOG.info(_("After force-killing instances: %s"), instances)
         self.assertEqual(len(instances), 1)
-        self.assertEqual(task_states.POWERING_OFF, instances[0]['task_state'])
+        self.assertEqual(instances[0]['task_state'], None)
 
     def test_add_instance_fault(self):
         instance = self._create_fake_instance()