Fix hard-delete of instance with soft-deleted referential constraints

When hard-deleting an instance we first delete related records
but the code was not taking into account soft-deleted related
records which will result in the instance delete failing due to
a referential constraint because soft-deleted records are not
really deleted when it comes to table constraints.

This fixes the issue by simply passing read_deleted='yes' to the
related record model query in the hard delete path.

The related unit test is updated to cover this scenario and a
typo in that same test is also fixed here.

Change-Id: I9fc5a9cc40ceffc450c1fde1df7fb36581e9cc94
Closes-Bug: #1830438

nova/db/sqlalchemy/api.py

@@ -1792,7 +1792,11 @@ def instance_destroy(context, instance_uuid, constraint=None,
         key = 'instance_uuid' if model not in filtered_by_uuid else 'uuid'
         filter_ = {key: instance_uuid}
         if hard_delete:
-            model_query(context, model).filter_by(**filter_).delete()
+            # We need to read any soft-deleted related records to make sure
+            # and clean those up as well otherwise we can fail with ForeignKey
+            # constraint errors when hard deleting the instance.
+            model_query(context, model, read_deleted='yes').filter_by(
+                **filter_).delete()
         else:
             model_query(context, model).filter_by(**filter_).soft_delete()
 

nova/tests/unit/db/test_db_api.py

@@ -3070,13 +3070,27 @@ class InstanceTestCase(test.TestCase, ModelsObjectComparatorMixin):
 
         bdm_values = {
             'instance_uuid': uuid,
-            'device_name': 'fake_device',
+            'device_name': '/dev/vda',
             'source_type': 'volume',
             'destination_type': 'volume',
         }
         block_dev = block_device.BlockDeviceDict(bdm_values)
         db.block_device_mapping_create(self.ctxt, block_dev, legacy=False)
 
+        # Crate a second BDM that is soft-deleted to simulate that the
+        # volume was detached and the BDM was deleted before the instance
+        # was hard destroyed.
+        bdm2_values = {
+            'instance_uuid': uuid,
+            'device_name': '/dev/vdb',
+            'source_type': 'volume',
+            'destination_type': 'volume',
+        }
+        block_dev2 = block_device.BlockDeviceDict(bdm2_values)
+        bdm2 = db.block_device_mapping_create(
+            self.ctxt, block_dev2, legacy=False)
+        db.block_device_mapping_destroy(self.ctxt, bdm2.id)
+
         migration_values = {
             "status": "finished",
             "instance_uuid": uuid,
@@ -3122,7 +3136,7 @@ class InstanceTestCase(test.TestCase, ModelsObjectComparatorMixin):
             self.assertEqual(0, len(instance_faults[uuid]))
             inst_bdms = db.block_device_mapping_get_all_by_instance(ctxt, uuid)
             self.assertEqual(0, len(inst_bdms))
-            filters = {"isntance_uuid": uuid}
+            filters = {"instance_uuid": uuid}
             inst_migrations = db.migration_get_all_by_filters(ctxt, filters)
             self.assertEqual(0, len(inst_migrations))
             vifs = db.virtual_interface_get_by_instance(ctxt, uuid)