Make Instance.refresh() extra careful about recursive loads

This simply makes sure that the instance copy that we fetch to
refresh an instance can not trigger lazy loads itself due to
a bug in get_by_uuid() or below. This hasn't actually been the
cause of any recent bugs, but this makes it much more careful.

It also makes sure that obj_load_attr() refuses to do its work
if self._context is None, which was previously only being
enforced for remoted calls.

Change-Id: I76f433af34620045b079e0a2c30c60b28a4ce525

nova/objects/instance.py

@@ -462,6 +462,11 @@ class Instance(base.NovaPersistentObject, base.NovaObject):
                        if self.obj_attr_is_set(field)]
         current = self.__class__.get_by_uuid(context, uuid=self.uuid,
                                              expected_attrs=extra)
+        # NOTE(danms): We orphan the instance copy so we do not unexpectedly
+        # trigger a lazy-load (which would mean we failed to calculate the
+        # expected_attrs properly)
+        current._context = None
+
         for field in self.fields:
             if self.obj_attr_is_set(field) and self[field] != current[field]:
                 self[field] = current[field]
@@ -472,6 +477,9 @@ class Instance(base.NovaPersistentObject, base.NovaObject):
             raise exception.ObjectActionError(
                 action='obj_load_attr',
                 reason='attribute %s not lazy-loadable' % attrname)
+        if not self._context:
+            raise exception.OrphanedObjectError(method='obj_load_attr',
+                                                objtype=self.obj_name())
 
         LOG.debug(_("Lazy-loading `%(attr)s' on %(name) uuid %(uuid)s"),
                   {'attr': attrname,

nova/objects/service.py

@@ -70,6 +70,9 @@ class Service(base.NovaPersistentObject, base.NovaObject):
         return service
 
     def obj_load_attr(self, attrname):
+        if not self._context:
+            raise exception.OrphanedObjectError(method='obj_load_attr',
+                                                objtype=self.obj_name())
         LOG.debug(_("Lazy-loading `%(attr)s' on %(name)s id %(id)s"),
                   {'attr': attrname,
                    'name': self.obj_name(),

nova/tests/objects/test_instance.py

@@ -171,6 +171,7 @@ class _TestInstanceObject(object):
 
     def test_load_invalid(self):
         inst = instance.Instance()
+        inst._context = self.context
         inst.uuid = 'fake-uuid'
         self.assertRaises(exception.ObjectActionError,
                           inst.obj_load_attr, 'foo')
@@ -214,6 +215,20 @@ class _TestInstanceObject(object):
         self.assertRemotes()
         self.assertEqual(set([]), inst.obj_what_changed())
 
+    def test_refresh_does_not_recurse(self):
+        inst = instance.Instance()
+        inst._context = self.context
+        inst.uuid = 'fake-uuid'
+        inst.metadata = {}
+        inst_copy = instance.Instance()
+        inst_copy.uuid = inst.uuid
+        self.mox.StubOutWithMock(instance.Instance, 'get_by_uuid')
+        instance.Instance.get_by_uuid(self.context, uuid=inst.uuid,
+                                      expected_attrs=['metadata']
+                                      ).AndReturn(inst_copy)
+        self.mox.ReplayAll()
+        self.assertRaises(exception.OrphanedObjectError, inst.refresh)
+
     def _save_test_helper(self, cell_type, save_kwargs):
         """Common code for testing save() for cells/non-cells."""
         if cell_type:

nova/tests/objects/test_service.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 from nova import db
+from nova import exception
 from nova.objects import service
 from nova.openstack.common import timeutils
 from nova.tests.objects import test_compute_node
@@ -165,6 +166,12 @@ class _TestServiceObject(object):
         # Make sure it doesn't re-fetch this
         service_obj.compute_node
 
+    def test_load_when_orphaned(self):
+        service_obj = service.Service()
+        service_obj.id = 123
+        self.assertRaises(exception.OrphanedObjectError,
+                          getattr, service_obj, 'compute_node')
+
 
 class TestServiceObject(test_objects._LocalTest,
                         _TestServiceObject):