Merge "Fix NoneType error in _notify_volume_usage_detach" into stable/pike

nova/compute/manager.py

@@ -4958,13 +4958,14 @@ class ComputeManager(manager.Manager):
         if CONF.volume_usage_poll_interval <= 0:
             return
 
-        vol_stats = []
         mp = bdm.device_name
         # Handle bootable volumes which will not contain /dev/
         if '/dev/' in mp:
             mp = mp[5:]
         try:
             vol_stats = self.driver.block_stats(instance, mp)
+            if vol_stats is None:
+                return
         except NotImplementedError:
             return
 

nova/tests/unit/compute/test_compute_mgr.py

@@ -4202,6 +4202,23 @@ class ComputeManagerUnitTestCase(test.NoDBTestCase):
                 mock.call(self.context, inst_obj, 'fake-mini',
                           action='soft_delete', phase='end')])
 
+    def test_notify_volume_usage_detach_no_block_stats(self):
+        """Tests the case that the virt driver returns None from the
+        block_stats() method and no notification is sent, similar to the
+        virt driver raising NotImplementedError.
+        """
+        self.flags(volume_usage_poll_interval=60)
+        fake_instance = objects.Instance()
+        fake_bdm = objects.BlockDeviceMapping(device_name='/dev/vda')
+        with mock.patch.object(self.compute.driver, 'block_stats',
+                               return_value=None) as block_stats:
+            # Assert a notification isn't sent.
+            with mock.patch.object(self.compute.notifier, 'info',
+                                   new_callable=mock.NonCallableMock):
+                self.compute._notify_volume_usage_detach(
+                    self.context, fake_instance, fake_bdm)
+        block_stats.assert_called_once_with(fake_instance, 'vda')
+
 
 class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
     def setUp(self):

nova/virt/driver.py

@@ -1262,6 +1262,13 @@ class ComputeDriver(object):
         unused.
 
         Note that this function takes an instance ID.
+
+        :param instance: nova.objects.Instance to get block storage statistics
+        :param disk_id: mountpoint name, e.g. "vda"
+        :returns: None if block statistics could not be retrieved, otherwise a
+            list of the form: [rd_req, rd_bytes, wr_req, wr_bytes, errs]
+        :raises: NotImplementedError if the driver does not implement this
+            method
         """
         raise NotImplementedError()