Properly clean up BDMs when _provision_instances fails

_provision_instances calls create_db_entry_for_new_instance
which creates the instance and block device mappings in the
database.

The instance is added to the instances list which is used
in the global exception block at the bottom of _provision_instances
to destroy any instances created. A failure that can trigger
this cleanup attempt after the instance and BDMs are created
is when checking server group member count fails with OverQuota.

The problem is that we fail to (soft) delete the block device mappings
that we created. Since there is a foreign key constraint between
the block_device_mapping and instances tables in the database,
when we try to archive (copy soft deleted things to shadow tables
and then hard-delete them) the deleted instance it will fail on
a referential constraint error due to the BDM(s) which weren't deleted.

We can fix this by deleting the BDMs when deleting the instance just
like we do for other reference tables.

A functional test is added to demonstrate the failure and fix which
also has the nice benefit of functionally testing the server group
member overquota error handling.

Change-Id: Ida66a93031046bafcf30c95ca232fb6382c2597b
Closes-Bug: #1569641
(cherry picked from commit 5674e7646d)

nova/db/sqlalchemy/api.py

@@ -1952,6 +1952,9 @@ def instance_destroy(context, instance_uuid, constraint=None):
     model_query(context, models.InstanceGroupMember).\
             filter_by(instance_id=instance_uuid).\
             soft_delete()
+    model_query(context, models.BlockDeviceMapping).\
+            filter_by(instance_uuid=instance_uuid).\
+            soft_delete()
     # NOTE(snikitin): We can't use model_query here, because there is no
     # column 'deleted' in 'tags' table.
     context.session.query(models.Tag).filter_by(

nova/tests/functional/test_server_group.py

@@ -18,6 +18,9 @@ import time
 
 from oslo_config import cfg
 
+from nova import context
+from nova import db
+from nova.db.sqlalchemy import api as db_api
 from nova import test
 from nova.tests import fixtures as nova_fixtures
 from nova.tests.functional.api import client
@@ -265,6 +268,33 @@ class ServerGroupTestV2(ServerGroupTestBase):
             self.assertIn(server['id'], members)
             self.assertEqual(host, server['OS-EXT-SRV-ATTR:host'])
 
+    def test_boot_servers_with_affinity_overquota(self):
+        # Tests that we check server group member quotas and cleanup created
+        # resources when we fail with OverQuota.
+        self.flags(quota_server_group_members=1)
+        # make sure we start with 0 servers
+        servers = self.api.get_servers(detail=False)
+        self.assertEqual(0, len(servers))
+        created_group = self.api.post_server_groups(self.affinity)
+        ex = self.assertRaises(client.OpenStackApiException,
+                               self._boot_servers_to_group,
+                               created_group)
+        self.assertEqual(403, ex.response.status_code)
+        # _boot_servers_to_group creates 2 instances in the group in order, not
+        # multiple servers in a single request. Since our quota is 1, the first
+        # server create would pass, the second should fail, and we should be
+        # left with 1 server and it's 1 block device mapping.
+        servers = self.api.get_servers(detail=False)
+        self.assertEqual(1, len(servers))
+        ctxt = context.get_admin_context()
+        servers = db.instance_get_all(ctxt)
+        self.assertEqual(1, len(servers))
+        ctxt_mgr = db_api.get_context_manager(ctxt)
+        with ctxt_mgr.reader.using(ctxt):
+            bdms = db_api._block_device_mapping_get_query(ctxt).all()
+        self.assertEqual(1, len(bdms))
+        self.assertEqual(servers[0]['uuid'], bdms[0]['instance_uuid'])
+
     def test_boot_servers_with_affinity_no_valid_host(self):
         created_group = self.api.post_server_groups(self.affinity)
         # Using big enough flavor to use up the resources on the host

nova/tests/unit/db/test_db_api.py

@@ -2773,6 +2773,23 @@ class InstanceTestCase(test.TestCase, ModelsObjectComparatorMixin):
         system_meta = db.instance_system_metadata_get(ctxt, instance['uuid'])
         self.assertEqual('baz', system_meta['original_image_ref'])
 
+    def test_delete_block_device_mapping_on_instance_destroy(self):
+        # Makes sure that the block device mapping is deleted when the
+        # related instance is deleted.
+        ctxt = context.get_admin_context()
+        instance = db.instance_create(ctxt, dict(display_name='bdm-test'))
+        bdm = {
+            'volume_id': uuidutils.generate_uuid(),
+            'device_name': '/dev/vdb',
+            'instance_uuid': instance['uuid'],
+        }
+        bdm = db.block_device_mapping_create(ctxt, bdm, legacy=False)
+        db.instance_destroy(ctxt, instance['uuid'])
+        # make sure the bdm is deleted as well
+        bdms = db.block_device_mapping_get_all_by_instance(
+            ctxt, instance['uuid'])
+        self.assertEqual([], bdms)
+
     def test_delete_instance_metadata_on_instance_destroy(self):
         ctxt = context.get_admin_context()
         # Create an instance with some metadata