Error out migration when confirm_resize fails

If anything fails and raises an exception during
confirm_resize, the migration status is stuck in
"confirming" status even though the instance status
may be "ERROR".

This change adds the errors_out_migration decorator
to the confirm_resize method to make sure the migration
status is "error" if an error is raised.

In bug 1821594 it was the driver.confirm_migration
method that raised some exception, so a unit test is
added here which simulates a similar scenario.

This only partially closes the bug because we are still
leaking allocations on the source node resource provider
since _delete_allocation_after_move is not called. That
will be dealt with in a separate patch.

Conflicts:
      nova/tests/functional/test_servers.py
      nova/tests/unit/compute/test_compute_mgr.py

NOTE(mriedem): The functional test conflict is due to not
having change I99427a52676826990d2a2ffc82cf30ad945b939c
in Rocky. The unit test conflict is due to not having
change I0851e2d54a1fdc82fe3291fb7e286e790f121e92 in Rocky.
The source_node attribute on the fake Migration object in
the unit test is added here because change
I312d61383345ea0ac1ab0c277b4c468e6aa94656 is not in Rocky.

Change-Id: Ic7d78ad43a2bad7f932c22c98944accbbed9e9e2
Partial-Bug: #1821594
(cherry picked from commit 408ef8f)
(cherry picked from commit 972d4e0)

Author: mriedem

nova/compute/manager.py

@@ -3825,6 +3825,7 @@ def change_instance_metadata(self, context, diff, instance):
 
     @wrap_exception()
     @wrap_instance_event(prefix='compute')
+    @errors_out_migration
     @wrap_instance_fault
     def confirm_resize(self, context, instance, migration):
         """Confirms a migration/resize and deletes the 'old' instance.

nova/tests/unit/compute/test_compute_mgr.py

@@ -6628,6 +6628,7 @@ def setUp(self):
                 expected_attrs=['metadata', 'system_metadata', 'info_cache'])
         self.migration = objects.Migration(
             context=self.context.elevated(),
+            id=1,
             uuid=uuids.migration_uuid,
             instance_uuid=self.instance.uuid,
             new_instance_type_id=7,
@@ -7043,6 +7044,53 @@ def do_it(mock_rc, mock_grt):
                 mock_resources.return_value)
         do_it()
 
+    @mock.patch('nova.compute.utils.add_instance_fault_from_exc')
+    @mock.patch('nova.objects.Migration.get_by_id')
+    @mock.patch('nova.objects.Instance.get_by_uuid')
+    @mock.patch('nova.compute.utils.notify_about_instance_usage')
+    @mock.patch('nova.compute.utils.notify_about_instance_action')
+    @mock.patch('nova.objects.Instance.save')
+    def test_confirm_resize_driver_confirm_migration_fails(
+            self, instance_save, notify_action, notify_usage,
+            instance_get_by_uuid, migration_get_by_id, add_fault):
+        """Tests the scenario that driver.confirm_migration raises some error
+        to make sure the error is properly handled, like the instance and
+        migration status is set to 'error'.
+        """
+        self.migration.status = 'confirming'
+        migration_get_by_id.return_value = self.migration
+        instance_get_by_uuid.return_value = self.instance
+
+        error = exception.HypervisorUnavailable(
+            host=self.migration.source_compute)
+        with test.nested(
+            mock.patch.object(self.compute, 'network_api'),
+            mock.patch.object(self.compute.driver, 'confirm_migration',
+                              side_effect=error)
+        ) as (
+            network_api, confirm_migration
+        ):
+            self.assertRaises(exception.HypervisorUnavailable,
+                              self.compute.confirm_resize,
+                              self.context, self.instance, self.migration)
+        # Make sure the instance is in ERROR status.
+        self.assertEqual(vm_states.ERROR, self.instance.vm_state)
+        # Make sure the migration is in error status.
+        self.assertEqual('error', self.migration.status)
+        # Instance.save is called twice, once to clear the resize metadata
+        # and once to set the instance to ERROR status.
+        self.assertEqual(2, instance_save.call_count)
+        # The migration.status should have been saved.
+        self.migration.save.assert_called_once_with()
+        # Assert other mocks we care less about.
+        notify_usage.assert_called_once()
+        notify_action.assert_called_once()
+        add_fault.assert_called_once()
+        confirm_migration.assert_called_once()
+        network_api.setup_networks_on_host.assert_called_once()
+        instance_get_by_uuid.assert_called_once()
+        migration_get_by_id.assert_called_once()
+
     @mock.patch('nova.scheduler.utils.resources_from_flavor')
     def test_delete_allocation_after_move_confirm_by_migration(self, mock_rff):
         mock_rff.return_value = {}