Merge "Provide original fault message when BFV fails" into stable/newton

nova/compute/manager.py

@@ -1594,10 +1594,14 @@ class ComputeManager(manager.Manager):
             LOG.warning(msg, instance=instance)
             raise exception.VolumeLimitExceeded()
 
-        except Exception:
+        except Exception as ex:
             LOG.exception(_LE('Instance failed block device setup'),
                           instance=instance)
-            raise exception.InvalidBDM()
+            # InvalidBDM will eventually result in a BuildAbortException when
+            # booting from volume, and will be recorded as an instance fault.
+            # Maintain the original exception message which most likely has
+            # useful details which the standard InvalidBDM error message lacks.
+            raise exception.InvalidBDM(six.text_type(ex))
 
     def _update_instance_after_spawn(self, context, instance):
         instance.power_state = self._get_power_state(context, instance)

nova/tests/unit/compute/test_compute_mgr.py

@@ -4136,6 +4136,28 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
         mock_prep.assert_called_once_with(self.context, self.instance,
                 self.block_device_mapping)
 
+    @mock.patch('nova.virt.block_device.attach_block_devices',
+                side_effect=exception.VolumeNotCreated('oops!'))
+    def test_prep_block_device_maintain_original_error_message(self,
+                                                               mock_attach):
+        """Tests that when attach_block_devices raises an Exception, the
+        re-raised InvalidBDM has the original error message which contains
+        the actual details of the failure.
+        """
+        bdms = objects.BlockDeviceMappingList(
+            objects=[fake_block_device.fake_bdm_object(
+                self.context,
+                dict(source_type='image',
+                     destination_type='volume',
+                     boot_index=0,
+                     image_id=uuids.image_id,
+                     device_name='/dev/vda',
+                     volume_size=1))])
+        ex = self.assertRaises(exception.InvalidBDM,
+                               self.compute._prep_block_device,
+                               self.context, self.instance, bdms)
+        self.assertEqual('oops!', six.text_type(ex))
+
     def test_failed_bdm_prep_from_delete_raises_unexpected(self):
         with test.nested(
                 mock.patch.object(self.compute,