libvirt: make live migration possible with Virtuozzo

Live migration for Libvirt vz driver works the same
way as for qemu. However some migration capabilities
are supported differently:
* Virtuozzo containers doesn't use backing file, so
we shouldn't ensure it exists in pre live migration.
* migrate_disks parameter doesn't make sense for
Virtuozzo, as backend determines whether specific
block device should be migrated or not.
* Passing new domain xml to migration method is not
supported.

Implements: blueprint live-migration-vz-driver
Change-Id: I89ecdef13ad47800abc8a5158f8834e46750b9ea
Signed-off-by: Pavel Gluschak <pglushchak@virtuozzo.com>

doc/source/support-matrix.ini

@@ -313,8 +313,8 @@ driver-impl-vmware=missing
 driver-notes-vmware=https://bugs.launchpad.net/nova/+bug/1192192
 driver-impl-hyperv=complete
 driver-impl-ironic=missing
-driver-impl-libvirt-vz-vm=missing
+driver-impl-libvirt-vz-vm=complete
-driver-impl-libvirt-vz-ct=missing
+driver-impl-libvirt-vz-ct=complete
 
 [operation.force-live-migration-to-complete]
 title=Force live migration to complete

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

@@ -7638,6 +7638,60 @@ class LibvirtConnTestCase(test.NoDBTestCase):
                           self.context, instance_ref, 'dest',
                           False, migrate_data, guest, [])
 
+    def test_live_migration_parallels_no_new_xml(self):
+        self.flags(virt_type='parallels', group='libvirt')
+        self.flags(enabled=False, group='vnc')
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI())
+        instance_dict = dict(self.test_instance)
+        instance_dict.update({'host': 'fake',
+                              'power_state': power_state.RUNNING,
+                              'vm_state': vm_states.ACTIVE})
+        instance = objects.Instance(**instance_dict)
+        migrate_data = objects.LibvirtLiveMigrateData(
+            block_migration=False)
+        dom_mock = mock.MagicMock()
+        guest = libvirt_guest.Guest(dom_mock)
+        drvr._live_migration_operation(self.context, instance, 'dest',
+                                       False, migrate_data, guest, [])
+        # when new xml is not passed we fall back to migrateToURI
+        dom_mock.migrateToURI.assert_called_once_with(
+            drvr._live_migration_uri('dest'),
+            flags=0, bandwidth=0)
+
+    @mock.patch.object(utils, 'spawn')
+    @mock.patch.object(host.Host, 'get_guest')
+    @mock.patch.object(fakelibvirt.Connection, '_mark_running')
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_live_migration_monitor')
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_live_migration_copy_disk_paths')
+    def test_live_migration_parallels_no_migrate_disks(self,
+                                                       mock_copy_disk_paths,
+                                                       mock_monitor,
+                                                       mock_running,
+                                                       mock_guest,
+                                                       mock_thread):
+        self.flags(virt_type='parallels', group='libvirt')
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI())
+        instance_dict = dict(self.test_instance)
+        instance_dict.update({'host': 'fake',
+                              'power_state': power_state.RUNNING,
+                              'vm_state': vm_states.ACTIVE})
+        instance = objects.Instance(**instance_dict)
+        migrate_data = objects.LibvirtLiveMigrateData(
+            block_migration=True)
+        dom = fakelibvirt.Domain(drvr._get_connection(), '<domain/>', True)
+        guest = libvirt_guest.Guest(dom)
+        mock_guest.return_value = guest
+        drvr._live_migration(self.context, instance, 'dest',
+                             lambda: None, lambda: None, True,
+                             migrate_data)
+        self.assertFalse(mock_copy_disk_paths.called)
+        mock_thread.assert_called_once_with(
+            drvr._live_migration_operation,
+            self.context, instance, 'dest', True,
+            migrate_data, guest, [])
+
     def test_live_migration_update_volume_xml(self):
         self.compute = manager.ComputeManager()
         instance_dict = dict(self.test_instance)
@@ -7798,9 +7852,9 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             ('xen', 'xenmigr://%s/system'),
             ('kvm', 'qemu+tcp://%s/system'),
             ('qemu', 'qemu+tcp://%s/system'),
+            ('parallels', 'parallels+tcp://%s/system'),
             # anything else will return None
             ('lxc', None),
-            ('parallels', None),
         )
         dest = 'destination'
         for hyperv, uri in hypervisor_uri_map:
@@ -9420,6 +9474,17 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         # Assert that we did nothing
         self.assertEqual({}, fake_backend.created_disks)
 
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_fetch_instance_kernel_ramdisk')
+    def test_create_images_and_backing_parallels(self, mock_fetch):
+        self.flags(virt_type='parallels', group='libvirt')
+        instance = objects.Instance(**self.test_instance)
+        instance.vm_mode = fields.VMMode.EXE
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI())
+        drvr._create_images_and_backing(self.context, instance,
+                                        '/fake/instance/dir', None)
+        self.assertFalse(mock_fetch.called)
+
     def _generate_target_ret(self, target_connect_addr=None):
         target_ret = {
         'graphics_listen_addrs': {'spice': '127.0.0.1', 'vnc': '127.0.0.1'},

nova/virt/libvirt/driver.py

@@ -681,12 +681,11 @@ class LibvirtDriver(driver.ComputeDriver):
 
     @staticmethod
     def _live_migration_uri(dest):
-        # Only Xen and QEMU support live migration, see
-        # https://libvirt.org/migration.html#scenarios for reference
         uris = {
             'kvm': 'qemu+tcp://%s/system',
             'qemu': 'qemu+tcp://%s/system',
             'xen': 'xenmigr://%s/system',
+            'parallels': 'parallels+tcp://%s/system',
         }
         virt_type = CONF.libvirt.virt_type
         uri = CONF.libvirt.live_migration_uri or uris.get(virt_type)
@@ -6036,11 +6035,13 @@ class LibvirtDriver(driver.ComputeDriver):
                     migrate_uri = self._migrate_uri(dest)
 
             params = None
-            new_xml_str = libvirt_migrate.get_updated_guest_xml(
+            new_xml_str = None
-                # TODO(sahid): It's not a really good idea to pass
+            if CONF.libvirt.virt_type != "parallels":
-                # the method _get_volume_config and we should to find
+                new_xml_str = libvirt_migrate.get_updated_guest_xml(
-                # a way to avoid this in future.
+                    # TODO(sahid): It's not a really good idea to pass
-                guest, migrate_data, self._get_volume_config)
+                    # the method _get_volume_config and we should to find
+                    # a way to avoid this in future.
+                    guest, migrate_data, self._get_volume_config)
             if self._host.has_min_version(
                     MIN_LIBVIRT_BLOCK_LM_WITH_VOLUMES_VERSION):
                 params = {
@@ -6483,7 +6484,8 @@ class LibvirtDriver(driver.ComputeDriver):
 
         disk_paths = []
         device_names = []
-        if migrate_data.block_migration:
+        if (migrate_data.block_migration and
+                CONF.libvirt.virt_type != "parallels"):
             disk_paths, device_names = self._live_migration_copy_disk_paths(
                 context, instance, guest)
 
@@ -6792,6 +6794,12 @@ class LibvirtDriver(driver.ComputeDriver):
                not available.
 
         """
+
+        # Virtuozzo containers don't use backing file
+        if (CONF.libvirt.virt_type == "parallels" and
+                instance.vm_mode == fields.VMMode.EXE):
+            return
+
         if not disk_info:
             disk_info = []
 

releasenotes/notes/live-migration-vz-3236af37a522e411.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Live migration is supported for both Virtuozzo containers
+    and virtual machines when using virt_type=parallels.