Add functional confirm_migration_error test

This test checks if allocations have been
successfully cleaned up upon the driver failing
during "confirm_migration".

Change-Id: I9d6478f492351b58aa87b8f56e907ee633d6d1c6
Related-bug: #1821594

Author: rodrigogansobarbieri

nova/tests/functional/test_servers.py

@@ -2497,6 +2497,59 @@ def _resize_and_check_allocations(self, server, old_flavor, new_flavor,
             new_flavor=new_flavor, source_rp_uuid=source_rp_uuid,
             dest_rp_uuid=dest_rp_uuid)
 
+    def test_migration_confirm_resize_error(self):
+        source_hostname = self.compute1.host
+        dest_hostname = self.compute2.host
+
+        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._move_and_check_allocations(
+            server, request={'migrate': None}, old_flavor=self.flavor1,
+            new_flavor=self.flavor1, source_rp_uuid=source_rp_uuid,
+            dest_rp_uuid=dest_rp_uuid)
+
+        # Mock failure
+        def fake_confirm_migration(context, migration, instance, network_info):
+            raise exception.MigrationPreCheckError(
+                reason='test_migration_confirm_resize_error')
+
+        with mock.patch('nova.virt.fake.FakeDriver.'
+                        'confirm_migration',
+                        side_effect=fake_confirm_migration):
+
+            # Confirm the migration/resize and check the usages
+            post = {'confirmResize': None}
+            self.api.post_server_action(
+                server['id'], post, check_response_status=[204])
+            server = self._wait_for_state_change(self.api, server, 'ERROR')
+
+        # After confirming and error, we should have an allocation only on the
+        # destination host
+
+        self.assertFlavorMatchesUsage(dest_rp_uuid, self.flavor1)
+        self.assertRequestMatchesUsage({'VCPU': 0,
+                                        'MEMORY_MB': 0,
+                                        'DISK_GB': 0}, source_rp_uuid)
+        self.assertFlavorMatchesAllocation(self.flavor1, server['id'],
+                                           dest_rp_uuid)
+
+        self._run_periodics()
+
+        # Check we're still accurate after running the periodics
+
+        self.assertFlavorMatchesUsage(dest_rp_uuid, self.flavor1)
+        self.assertRequestMatchesUsage({'VCPU': 0,
+                                        'MEMORY_MB': 0,
+                                        'DISK_GB': 0}, source_rp_uuid)
+        self.assertFlavorMatchesAllocation(self.flavor1, server['id'],
+                                           dest_rp_uuid)
+
+        self._delete_and_check_allocations(server)
+
     def _test_resize_revert(self, dest_hostname):
         source_hostname = self._other_hostname(dest_hostname)
         source_rp_uuid = self._get_provider_uuid_by_host(source_hostname)