Libvirt: Allow missing volumes during delete

When deleting an instance, libvirt driver will clear all the volumes
of the instance. Ignore exception when clearing a missing volume
to avoid delete instance error.

Closes-Bug: 1404791
Change-Id: I8a663e8f0396bf2303642610ae1001c330159b75

nova/tests/unit/virt/libvirt/test_lvm.py

@@ -50,10 +50,20 @@ class LvmTestCase(test.NoDBTestCase):
         self.assertRaises(exception.VolumeBDMPathNotFound,
                           lvm.get_volume_size, '/dev/foo')
 
+    @mock.patch.object(utils, 'execute',
+                       side_effect=processutils.ProcessExecutionError(
+                            stderr=('blockdev: cannot open /dev/foo: '
+                                    'No such file or directory')))
+    def test_get_volume_size_not_found_file(self, mock_execute):
+        self.assertRaises(exception.VolumeBDMPathNotFound,
+            lvm.get_volume_size, '/dev/foo')
+
+    @mock.patch.object(libvirt_utils, 'path_exists', return_value=True)
     @mock.patch.object(utils, 'execute',
                        side_effect=processutils.ProcessExecutionError(
                             stderr='blockdev: i am sad in other ways'))
-    def test_get_volume_size_unexpectd_error(self, mock_execute):
+    def test_get_volume_size_unexpectd_error(self, mock_execute,
+                                             mock_path_exists):
         self.assertRaises(processutils.ProcessExecutionError,
                           lvm.get_volume_size, '/dev/foo')
 
@@ -168,6 +178,13 @@ class LvmTestCase(test.NoDBTestCase):
         lvm.clear_volume('/dev/vd')
         self.assertEqual(expected_commands, executes)
 
+    @mock.patch.object(utils, 'execute',
+                       side_effect=processutils.ProcessExecutionError(
+                                    stderr=('blockdev: cannot open /dev/foo: '
+                                            'No such file or directory')))
+    def test_lvm_clear_ignore_lvm_not_found(self, mock_execute):
+        lvm.clear_volume('/dev/foo')
+
     def test_fail_remove_all_logical_volumes(self):
         def fake_execute(*args, **kwargs):
             if 'vol2' in args:

nova/virt/libvirt/lvm.py

@@ -19,8 +19,6 @@
 #    under the License.
 #
 
-import functools
-
 from oslo_concurrency import processutils
 from oslo_config import cfg
 from oslo_log import log as logging
@@ -31,7 +29,6 @@ from nova import exception
 from nova.i18n import _
 from nova.i18n import _LE
 from nova.i18n import _LW
-from nova import utils as nova_utils
 from nova.virt.libvirt import utils
 
 
@@ -51,28 +48,6 @@ CONF.import_opt('instances_path', 'nova.compute.manager')
 LOG = logging.getLogger(__name__)
 
 
-@nova_utils.expects_func_args('path')
-def wrap_no_device_error(function):
-    """Wraps a method to catch exceptions related to volume BDM not found.
-
-    This decorator wraps a method to catch ProcessExecutionError having to do
-    with a missing volume block device mapping. It translates the error to a
-    VolumeBDMPathNotFound exception.
-    """
-
-    @functools.wraps(function)
-    def decorated_function(path):
-        try:
-            return function(path)
-        except processutils.ProcessExecutionError as e:
-            if 'No such device or address' in e.stderr:
-                raise exception.VolumeBDMPathNotFound(path=path)
-            else:
-                raise
-
-    return decorated_function
-
-
 def create_volume(vg, lv, size, sparse=False):
     """Create LVM image.
 
@@ -184,7 +159,6 @@ def volume_info(path):
     return dict(zip(*info))
 
 
-@wrap_no_device_error
 def get_volume_size(path):
     """Get logical volume size in bytes.
 
@@ -193,9 +167,14 @@ def get_volume_size(path):
              fails in some unexpected way.
     :raises: exception.VolumeBDMPathNotFound if the volume path does not exist.
     """
-    out, _err = utils.execute('blockdev', '--getsize64', path,
-                              run_as_root=True)
-
+    try:
+        out, _err = utils.execute('blockdev', '--getsize64', path,
+                                  run_as_root=True)
+    except processutils.ProcessExecutionError:
+        if not utils.path_exists(path):
+            raise exception.VolumeBDMPathNotFound(path=path)
+        else:
+            raise
     return int(out)
 
 
@@ -246,7 +225,13 @@ def clear_volume(path):
         return
 
     volume_clear_size = int(CONF.libvirt.volume_clear_size) * units.Mi
-    volume_size = get_volume_size(path)
+
+    try:
+        volume_size = get_volume_size(path)
+    except exception.VolumeBDMPathNotFound:
+        LOG.warn(_LW('ignoring missing logical volume %(path)s'),
+                 {'path': path})
+        return
 
     if volume_clear_size != 0 and volume_clear_size < volume_size:
         volume_size = volume_clear_size