Rolling Upgrades: Fix VolumeAttachment

When we added `connection_info` to the VolumeAttachment on
Idbc1049e8adf1d5b955bda01d58bb6b89fc6c5c7 we didn't add backporting
code, so rolling upgrades will break if a VolumeAttachment OVO is passed
between Cinder Services with different versions during an upgrade.

TrivialFix

Change-Id: I07101a2adfcbc81687a62d1d19bb97971d12a42d

cinder/objects/volume_attachment.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 from oslo_serialization import jsonutils
+from oslo_utils import versionutils
 from oslo_versionedobjects import fields
 
 from cinder import db
@@ -64,6 +65,14 @@ class VolumeAttachment(base.CinderPersistentObject, base.CinderObject,
     def _get_expected_attrs(cls, context, *args, **kwargs):
         return ['volume']
 
+    def obj_make_compatible(self, primitive, target_version):
+        """Make a object representation compatible with target version."""
+        super(VolumeAttachment, self).obj_make_compatible(primitive,
+                                                          target_version)
+        target_version = versionutils.convert_version_to_tuple(target_version)
+        if target_version < (1, 2):
+            primitive.pop('connection_info', None)
+
     @classmethod
     def _from_db_object(cls, context, attachment, db_attachment,
                         expected_attrs=None):

cinder/tests/unit/objects/test_volume_attachment.py

@@ -12,6 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import ddt
 import mock
 import six
 
@@ -22,6 +23,7 @@ from cinder.tests.unit import fake_volume
 from cinder.tests.unit import objects as test_objects
 
 
+@ddt.ddt
 class TestVolumeAttachment(test_objects.BaseObjectsTestCase):
 
     @mock.patch('cinder.db.sqlalchemy.api.volume_attachment_get')
@@ -96,6 +98,21 @@ class TestVolumeAttachment(test_objects.BaseObjectsTestCase):
         self.assertEqual(fields.VolumeAttachStatus.ATTACHED,
                          attachment.attach_status)
 
+    @ddt.data('1.0', '1.1', '1.2')
+    def test_obj_make_compatible(self, version):
+        connection_info = {'field': 'value'}
+        vol_attach = objects.VolumeAttachment(self.context,
+                                              connection_info=connection_info)
+        primitive = vol_attach.obj_to_primitive(version)
+        converted_vol_attach = objects.VolumeAttachment.obj_from_primitive(
+            primitive)
+        if version == '1.2':
+            self.assertEqual(connection_info,
+                             converted_vol_attach.connection_info)
+        else:
+            self.assertFalse(converted_vol_attach.obj_attr_is_set(
+                'connection_info'))
+
 
 class TestVolumeAttachmentList(test_objects.BaseObjectsTestCase):
     @mock.patch('cinder.db.volume_attachment_get_all_by_volume_id')