Don't lazy-load flavor.projects during destroy()

When we destroy a flavor it's happening in the API database now.
Right after we delete the flavor, we send a delete notification
which will attempt to lazy-load projects, but because the flavor
is deleted, that will result in a FlavorNotFound from the API DB
in method _get_projects_from_db. Because of our fallback code to
the main cell DB we'll then call flavor_access_get_by_flavor_id
which returns an empty list and that's what goes into the
notification, but it's not accurate since the empty list implies
there are/were no projects with access to that flavor, when in
reality we don't know.

This handles the delete notification case by orphaning the flavor
object so that when the notification emit happens, the
NotificationPayloadBase gets an OrphanedObjectError and just
sets projects to None, which is a better representation in the
notification payload that we don't have that data.

The tests needed some work since they were not actually comparing
the payload to the flavor object before, they were comparing to
fields in the DB representation of the flavor, which doesn't
include the projects field as it's a joined column.

Change-Id: I6868efab22cf9f1eb9006589a5b62618434c3ba3
Closes-Bug: #1687012

doc/notification_samples/flavor-delete.json

@@ -17,7 +17,7 @@
             "vcpu_weight": 0,
             "flavorid": "a22d5517-147c-4147-a0d1-e698df5cd4e3",
             "extra_specs": null,
-            "projects": []
+            "projects": null
         }
     },
     "event_type": "flavor.delete",

nova/objects/flavor.py

@@ -614,7 +614,12 @@ class Flavor(base.NovaPersistentObject, base.NovaObject,
         # lazy-load projects (which is a problem for instance-bound
         # flavors and compute-cell operations), just load them here.
         if 'projects' not in self:
-            self._load_projects()
+            # If the flavor is deleted we can't lazy-load projects.
+            # FlavorPayload will orphan the flavor which will make the
+            # NotificationPayloadBase set projects=None in the notification
+            # payload.
+            if action != fields.NotificationAction.DELETE:
+                self._load_projects()
         notification_type = flavor_notification.FlavorNotification
         payload_type = flavor_notification.FlavorPayload
 

nova/tests/unit/notifications/objects/test_flavor.py

@@ -21,6 +21,8 @@ from nova.objects import fields
 from nova import test
 from nova.tests.unit.objects.test_flavor import fake_flavor
 
+PROJECTS_SENTINEL = object()
+
 
 class TestFlavorNotification(test.TestCase):
     def setUp(self):
@@ -29,7 +31,8 @@ class TestFlavorNotification(test.TestCase):
 
     @mock.patch('nova.notifications.objects.flavor.FlavorNotification')
     def _verify_notification(self, flavor_obj, flavor, action,
-                             mock_notification, project_id=None):
+                             mock_notification, project_id=None,
+                             expected_projects=PROJECTS_SENTINEL):
         notification = mock_notification
         if action == "CREATE":
             flavor_obj.create()
@@ -61,8 +64,12 @@ class TestFlavorNotification(test.TestCase):
 
         schema = flavor_notification.FlavorPayload.SCHEMA
         for field in schema:
-            if field in flavor:
-                self.assertEqual(flavor[field], getattr(payload, field))
+            if field == 'projects' and expected_projects != PROJECTS_SENTINEL:
+                self.assertEqual(expected_projects, getattr(payload, field))
+            elif field in flavor_obj:
+                self.assertEqual(flavor_obj[field], getattr(payload, field))
+            else:
+                self.fail('Missing check for field %s in flavor_obj.' % field)
 
     @mock.patch('nova.objects.Flavor._flavor_create')
     def test_flavor_create_with_notification(self, mock_create):
@@ -117,6 +124,26 @@ class TestFlavorNotification(test.TestCase):
         mock_destroy.return_value = flavor
         flavor_obj = objects.Flavor(context=self.ctxt, **flavor)
         flavor_obj.obj_reset_changes()
+        self.assertNotIn('projects', flavor_obj)
+        # We specifically expect there to not be any projects as we don't want
+        # to try and lazy-load them from the main database and end up with [].
+        self._verify_notification(flavor_obj, flavor, "DELETE",
+                                  expected_projects=None)
+
+    @mock.patch('nova.objects.Flavor._flavor_destroy')
+    def test_flavor_destroy_with_notification_and_projects(self, mock_destroy):
+        """Tests the flavor-delete notification with flavor.projects loaded."""
+        flavor = copy.deepcopy(fake_flavor)
+        flavorid = '1'
+        flavor['flavorid'] = flavorid
+        flavor['id'] = flavorid
+        mock_destroy.return_value = flavor
+        flavor_obj = objects.Flavor(
+            context=self.ctxt, projects=['foo'], **flavor)
+        flavor_obj.obj_reset_changes()
+        self.assertIn('projects', flavor_obj)
+        self.assertEqual(['foo'], flavor_obj.projects)
+        # Since projects is loaded we shouldn't try to lazy-load it.
         self._verify_notification(flavor_obj, flavor, "DELETE")
 
     def test_obj_make_compatible(self):