Correct deleted_at value in notification messages

The deleted_at value in notification messages is currently
set from the terminated_at value in the instance record.

A comment in the code says this is to avoid confusion between
terminated_at and deleted_at,  but swapping the names doesn't
seem to be a great way to address that.

In practice "terminated and not deleted" is a transient state
unless an error occurs, and the time gap is very short.  But
deleted_at is always set when the entry is deleted in the DB,
whereas terminated_at can be left unset in some error cases.

Rather than present terminated_at as the deleted_at value in
the message we include both and let the recipient decide which
they want to use.

Fixes bug: 1227080

Change-Id: Ic67f66b6c64be1a8f43f4fdd5b1fac25f1414247

nova/notifications.py

@@ -381,10 +381,11 @@ def null_safe_isotime(s):
 
         # Date properties
         created_at=str(instance_ref['created_at']),
-        # Nova's deleted vs terminated instance terminology is confusing,
-        # this should be when the instance was deleted (i.e. terminated_at),
-        # not when the db record was deleted. (mdragon)
-        deleted_at=null_safe_isotime(instance_ref.get('terminated_at')),
+        # Terminated and Deleted are slightly different (although being
+        # terminated and not deleted is a transient state), so include
+        # both and let the recipient decide which they want to use.
+        terminated_at=null_safe_isotime(instance_ref.get('terminated_at')),
+        deleted_at=null_safe_isotime(instance_ref.get('deleted_at')),
         launched_at=null_safe_isotime(instance_ref.get('launched_at')),
 
         # Image properties

nova/tests/compute/test_compute.py

@@ -2872,8 +2872,9 @@ def test_terminate_usage_notification(self):
         self.assertTrue('display_name' in payload)
         self.assertTrue('created_at' in payload)
         self.assertTrue('launched_at' in payload)
+        self.assertTrue('terminated_at' in payload)
         self.assertTrue('deleted_at' in payload)
-        self.assertEqual(payload['deleted_at'], timeutils.strtime(cur_time))
+        self.assertEqual(payload['terminated_at'], timeutils.strtime(cur_time))
         image_ref_url = glance.generate_image_url(FAKE_IMAGE_REF)
         self.assertEquals(payload['image_ref_url'], image_ref_url)