Add functional test to delete a server while in VERIFY_RESIZE

This scenario came up while discussing what might be causing
leaked resource allocations in Placement [1].

I fully expected the new test to fail because I couldn't see
from the compute manager where the migration-based allocations
would be cleaned up when deleting the server. It turns out that
when deleting a VERIFY_RESIZE server, the API confirms the resize
which drops the migration-based allocations on the source node
before deleting the server on the target node.

Since this is not obvious, a comment in the compute API
_confirm_resize_on_deleting() method is added.

[1] http://lists.openstack.org/pipermail/openstack-dev/2018-November/136295.html

Change-Id: I4c12502c86c7ac27369d119e0f97768cf41695b5

nova/compute/api.py

@@ -2134,7 +2134,9 @@ class API(base.Base):
 
     def _confirm_resize_on_deleting(self, context, instance):
         # If in the middle of a resize, use confirm_resize to
-        # ensure the original instance is cleaned up too
+        # ensure the original instance is cleaned up too along
+        # with its allocations (and migration-based allocations)
+        # in placement.
         migration = None
         for status in ('finished', 'confirming'):
             try:

nova/tests/functional/integrated_helpers.py

@@ -40,6 +40,7 @@ from nova.tests.unit import cast_as_call
 from nova.tests.unit import fake_notifier
 import nova.tests.unit.image.fake
 from nova.tests.unit import policy_fixture
+from nova import utils
 from nova.virt import fake
 
 
@@ -714,9 +715,26 @@ class ProviderUsageBaseTestCase(test.TestCase, InstanceHelperMixin):
     def _delete_and_check_allocations(self, server):
         """Delete the instance and asserts that the allocations are cleaned
 
+        If the server was moved (resized or live migrated), also checks that
+        migration-based allocations are also cleaned up.
+
         :param server: The API representation of the instance to be deleted
         """
 
+        # First check to see if there is a related migration record so we can
+        # assert its allocations (if any) are not leaked.
+        with utils.temporary_mutation(self.admin_api, microversion='2.59'):
+            migrations = self.admin_api.api_get(
+                '/os-migrations?instance_uuid=%s' %
+                server['id']).body['migrations']
+        if migrations:
+            # If there is more than one migration, they are sorted by
+            # created_at in descending order so we'll get the last one
+            # which is probably what we'd always want anyway.
+            migration_uuid = migrations[0]['uuid']
+        else:
+            migration_uuid = None
+
         self.api.delete_server(server['id'])
         self._wait_until_deleted(server)
         # NOTE(gibi): The resource allocation is deleted after the instance is
@@ -737,6 +755,11 @@ class ProviderUsageBaseTestCase(test.TestCase, InstanceHelperMixin):
         allocations = self._get_allocations_by_server_uuid(server['id'])
         self.assertEqual(0, len(allocations))
 
+        if migration_uuid:
+            # and no allocations for the delete migration
+            allocations = self._get_allocations_by_server_uuid(migration_uuid)
+            self.assertEqual(0, len(allocations))
+
     def _run_periodics(self):
         """Run the update_available_resource task on every compute manager
 

nova/tests/functional/test_servers.py

@@ -2688,6 +2688,28 @@ class ServerMovingTests(integrated_helpers.ProviderUsageBaseTestCase):
 
         self._delete_and_check_allocations(server)
 
+    def test_resize_delete_while_verify(self):
+        """Test scenario where the server is deleted while in the
+        VERIFY_RESIZE state and ensures the allocations are properly
+        cleaned up from the source and target compute node resource providers.
+        The _confirm_resize_on_deleting() method in the API is actually
+        responsible for making sure the migration-based allocations get
+        cleaned up by confirming the resize on the source host before deleting
+        the server from the target host.
+        """
+        dest_hostname = 'host2'
+        source_hostname = self._other_hostname(dest_hostname)
+        source_rp_uuid = self._get_provider_uuid_by_host(source_hostname)
+        dest_rp_uuid = self._get_provider_uuid_by_host(dest_hostname)
+
+        server = self._boot_and_check_allocations(self.flavor1,
+                                                  source_hostname)
+
+        self._resize_and_check_allocations(server, self.flavor1, self.flavor2,
+                                           source_rp_uuid, dest_rp_uuid)
+
+        self._delete_and_check_allocations(server)
+
     def _wait_for_notification_event_type(self, event_type, max_retries=50):
         retry_counter = 0
         while True: