libvirt: Refresh volume connection_info after volume snapshot

The following patch is related to the guest assisted snapshot
functionality.  When you take a snapshot of a volume
(e.g. GlusterFS) attached to a running instance, a new snapshot
file is created, i.e. volume-<uuid>.<snapshot-uuid>.  The
instance uses this file as the active volume.  If you shutdown
and restart the instance, nova will reattach the base volume
(volume-<uuid>) to the instance instead of the snapshot volume
(volume-<uuid>.<snapshot-uuid>).  The expected behavior is to
have the snapshot volume reattach to the instance.  This is
caused by stale data being returned from the database when
_get_instance_volume_block_device_info is called during
_power_on.  To fix this bug, this patch calls
refresh_connection_info to update the database in both
volume_snapshot_create and _volume_snapshot_delete methods of the
libvirt driver.

Change-Id: I0f340a3f879580e7981d97863bc299e33d71aa84
Closes-Bug: #1304695

nova/tests/virt/libvirt/test_libvirt.py

@@ -55,6 +55,7 @@
 from nova.openstack.common import uuidutils
 from nova.pci import pci_manager
 from nova import test
+from nova.tests import fake_block_device
 from nova.tests import fake_instance
 from nova.tests import fake_network
 import nova.tests.image.fake
@@ -8808,6 +8809,29 @@ def setUp(self):
     def tearDown(self):
         super(LibvirtVolumeSnapshotTestCase, self).tearDown()
 
+    @mock.patch('nova.virt.block_device.DriverVolumeBlockDevice.'
+                'refresh_connection_info')
+    @mock.patch('nova.objects.block_device.BlockDeviceMapping.'
+                'get_by_volume_id')
+    def test_volume_refresh_connection_info(self, mock_get_by_volume_id,
+                                            mock_refresh_connection_info):
+        fake_bdm = fake_block_device.FakeDbBlockDeviceDict({
+            'id': 123,
+            'instance_uuid': 'fake-instance',
+            'device_name': '/dev/sdb',
+            'source_type': 'volume',
+            'destination_type': 'volume',
+            'volume_id': 'fake-volume-id-1',
+            'connection_info': '{"fake": "connection_info"}'})
+        mock_get_by_volume_id.return_value = fake_bdm
+
+        self.conn._volume_refresh_connection_info(self.c, self.inst,
+                                                  self.volume_uuid)
+
+        mock_get_by_volume_id.assert_called_once_with(self.c, self.volume_uuid)
+        mock_refresh_connection_info.assert_called_once_with(self.c, self.inst,
+            self.conn._volume_api, self.conn)
+
     def test_volume_snapshot_create(self, quiesce=True):
         CONF.instance_name_template = 'instance-%s'
         self.mox.StubOutWithMock(self.conn, '_lookup_by_name')
@@ -8882,6 +8906,13 @@ def test_volume_snapshot_create_outer_success(self):
         self.conn._volume_api.update_snapshot_status(
             self.c, self.create_info['snapshot_id'], 'creating')
 
+        self.mox.StubOutWithMock(self.conn._volume_api, 'get_snapshot')
+        self.conn._volume_api.get_snapshot(self.c,
+            self.create_info['snapshot_id']).AndReturn({'status': 'available'})
+        self.mox.StubOutWithMock(self.conn, '_volume_refresh_connection_info')
+        self.conn._volume_refresh_connection_info(self.c, instance,
+                                                  self.volume_uuid)
+
         self.mox.ReplayAll()
 
         self.conn.volume_snapshot_create(self.c, instance, self.volume_uuid,
@@ -9001,6 +9032,10 @@ def test_volume_snapshot_delete_outer_success(self):
         self.conn._volume_api.update_snapshot_status(
             self.c, snapshot_id, 'deleting')
 
+        self.mox.StubOutWithMock(self.conn, '_volume_refresh_connection_info')
+        self.conn._volume_refresh_connection_info(self.c, instance,
+                                                  self.volume_uuid)
+
         self.mox.ReplayAll()
 
         self.conn.volume_snapshot_delete(self.c, instance, self.volume_uuid,

nova/virt/libvirt/driver.py

@@ -70,6 +70,7 @@
 from nova import context as nova_context
 from nova import exception
 from nova.image import glance
+from nova.objects import block_device as block_device_obj
 from nova.objects import flavor as flavor_obj
 from nova.objects import instance as instance_obj
 from nova.objects import service as service_obj
@@ -89,6 +90,7 @@
 from nova import rpc
 from nova import utils
 from nova import version
+from nova.virt import block_device as driver_block_device
 from nova.virt import configdrive
 from nova.virt import cpu
 from nova.virt.disk import api as disk
@@ -1784,6 +1786,13 @@ def _volume_snapshot_create(self, context, instance, domain,
 
             raise
 
+    def _volume_refresh_connection_info(self, context, instance, volume_id):
+        bdm = block_device_obj.BlockDeviceMapping.get_by_volume_id(context,
+                                                                   volume_id)
+        driver_bdm = driver_block_device.DriverVolumeBlockDevice(bdm)
+        driver_bdm.refresh_connection_info(context, instance,
+                                           self._volume_api, self)
+
     def volume_snapshot_create(self, context, instance, volume_id,
                                create_info):
         """Create snapshots of a Cinder volume via libvirt.
@@ -1830,6 +1839,17 @@ def volume_snapshot_create(self, context, instance, volume_id,
         self._volume_snapshot_update_status(
             context, snapshot_id, 'creating')
 
+        def _wait_for_snapshot():
+            snapshot = self._volume_api.get_snapshot(context, snapshot_id)
+
+            if snapshot.get('status') != 'creating':
+                self._volume_refresh_connection_info(context, instance,
+                                                     volume_id)
+                raise loopingcall.LoopingCallDone()
+
+        timer = loopingcall.FixedIntervalLoopingCall(_wait_for_snapshot)
+        timer.start(interval=0.5).wait()
+
     def _volume_snapshot_delete(self, context, instance, volume_id,
                                 snapshot_id, delete_info=None):
         """Note:
@@ -1964,6 +1984,7 @@ def volume_snapshot_delete(self, context, instance, volume_id, snapshot_id,
                     context, snapshot_id, 'error_deleting')
 
         self._volume_snapshot_update_status(context, snapshot_id, 'deleting')
+        self._volume_refresh_connection_info(context, instance, volume_id)
 
     def reboot(self, context, instance, network_info, reboot_type='SOFT',
                block_device_info=None, bad_volumes_callback=None):