Avoid vm instance shutdown when power state is NOSTATE

* nova/compute/manager.py (_sync_power_states): Log the condition
where we can retrieve the state from the hyperviser, rather than
stopping the VM.

Related grizzly commits are 95e7770 and ad101ce

Fixes bug: 1085771
Change-Id: I5fb9fdc6bcde729c00c4931960ed0de3b8fa189d

nova/compute/manager.py

@@ -2737,9 +2737,8 @@ def _sync_power_states(self, context):
                 pass
             elif vm_state == vm_states.ACTIVE:
                 # The only rational power state should be RUNNING
-                if vm_power_state in (power_state.NOSTATE,
-                                       power_state.SHUTDOWN,
-                                       power_state.CRASHED):
+                if vm_power_state in (power_state.SHUTDOWN,
+                                      power_state.CRASHED):
                     LOG.warn(_("Instance shutdown by itself. Calling "
                                "the stop API."), instance=db_instance)
                     try:
@@ -2774,6 +2773,12 @@ def _sync_power_states(self, context):
                     # 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

@@ -2313,7 +2313,7 @@ def test_run_kill_vm(self):
         instances = db.instance_get_all(ctxt)
         LOG.info(_("After force-killing instances: %s"), instances)
         self.assertEqual(len(instances), 1)
-        self.assertEqual(task_states.STOPPING, instances[0]['task_state'])
+        self.assertEqual(instances[0]['task_state'], None)
 
     def test_add_instance_fault(self):
         exc_info = None