libvirt: Acquire TCP ports for console during live migration

During a live migration process we reserve serial ports on
destination host and update domain XML during migration to
use the new reserved ports from destination.

If the migration succeeds we release ports on the source host.
If the migration fails we release reserved ports on the
destination host.

Co-Authored-By: Sahid Ferdjaoui <sahid.ferdjaoui@redhat.com>
Change-Id: Ie2524191d22cca2287eb7dbaa22b74d43e43c896
Closes-Bug: #1455252

Author: markuszoeller

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

@@ -3615,15 +3615,21 @@ def test_get_guest_config_with_spice_and_agent(self):
         self.assertEqual(cfg.devices[5].type, "spice")
         self.assertEqual(cfg.devices[6].type, "qxl")
 
+    @mock.patch.object(host.Host, 'get_guest')
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_get_serial_ports_from_guest')
     @mock.patch('nova.console.serial.acquire_port')
     @mock.patch('nova.virt.hardware.get_number_of_serial_ports',
                 return_value=1)
     @mock.patch.object(libvirt_driver.libvirt_utils, 'get_arch',)
     def test_create_serial_console_devices_based_on_arch(self, mock_get_arch,
-                                           mock_get_port_number,
-                                           mock_acquire_port):
+                                                         mock_get_port_number,
+                                                         mock_acquire_port,
+                                                         mock_ports,
+                                                         mock_guest):
         self.flags(enabled=True, group='serial_console')
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        instance = objects.Instance(**self.test_instance)
 
         expected = {arch.X86_64: vconfig.LibvirtConfigGuestSerial,
                     arch.S390: vconfig.LibvirtConfigGuestConsole,
@@ -3635,40 +3641,44 @@ def test_create_serial_console_devices_based_on_arch(self, mock_get_arch,
             mock_get_arch.return_value = guest_arch
             guest = vconfig.LibvirtConfigGuest()
 
-            drvr._create_consoles(virt_type="kvm", guest=guest, log_path="",
-                                  flavor={}, image_meta={}, caps=caps)
+            drvr._create_consoles(virt_type="kvm", guest=guest,
+                                  instance=instance, flavor={},
+                                  image_meta={}, caps=caps)
             self.assertEqual(2, len(guest.devices))
             console_device = guest.devices[0]
             self.assertIsInstance(console_device, device_type)
             self.assertEqual("tcp", console_device.type)
 
+    @mock.patch.object(host.Host, 'get_guest')
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_get_serial_ports_from_guest')
     @mock.patch('nova.virt.hardware.get_number_of_serial_ports',
                 return_value=4)
     @mock.patch.object(libvirt_driver.libvirt_utils, 'get_arch',
                        side_effect=[arch.X86_64, arch.S390, arch.S390X])
     def test_create_serial_console_devices_with_limit_exceeded_based_on_arch(
-            self, mock_get_arch, mock_get_port_number):
+            self, mock_get_arch, mock_get_port_number, mock_ports, mock_guest):
         self.flags(enabled=True, group='serial_console')
         self.flags(virt_type="qemu", group='libvirt')
         flavor = 'fake_flavor'
         image_meta = objects.ImageMeta()
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         caps = drvr._host.get_capabilities()
         guest = vconfig.LibvirtConfigGuest()
-        log_path = ""
+        instance = objects.Instance(**self.test_instance)
         self.assertRaises(exception.SerialPortNumberLimitExceeded,
                           drvr._create_consoles,
-                          "kvm", guest, log_path, flavor, image_meta, caps)
+                          "kvm", guest, instance, flavor, image_meta, caps)
         mock_get_arch.assert_called_with(image_meta)
         mock_get_port_number.assert_called_with(flavor,
                                                 image_meta)
 
-        drvr._create_consoles("kvm", guest, log_path, flavor, image_meta, caps)
+        drvr._create_consoles("kvm", guest, instance, flavor, image_meta, caps)
         mock_get_arch.assert_called_with(image_meta)
         mock_get_port_number.assert_called_with(flavor,
                                                 image_meta)
 
-        drvr._create_consoles("kvm", guest, log_path, flavor, image_meta, caps)
+        drvr._create_consoles("kvm", guest, instance, flavor, image_meta, caps)
         mock_get_arch.assert_called_with(image_meta)
         mock_get_port_number.assert_called_with(flavor,
                                                 image_meta)
@@ -7903,24 +7913,27 @@ def test_update_volume_xml_no_connection_info(self):
                 drvr._get_volume_config)
             self.assertEqual(target_xml, config)
 
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_get_serial_ports_from_guest')
     @mock.patch.object(fakelibvirt.virDomain, "migrateToURI2")
     @mock.patch.object(fakelibvirt.virDomain, "XMLDesc")
     def test_live_migration_update_serial_console_xml(self, mock_xml,
-                                                      mock_migrate):
+                                                      mock_migrate, mock_get):
         self.compute = importutils.import_object(CONF.compute_manager)
         instance_ref = self.test_instance
 
         xml_tmpl = ("<domain type='kvm'>"
                     "<devices>"
                     "<console type='tcp'>"
-                    "<source mode='bind' host='{addr}' service='10000'/>"
+                    "<source mode='bind' host='{addr}' service='{port}'/>"
+                    "<target type='serial' port='0'/>"
                     "</console>"
                     "</devices>"
                     "</domain>")
 
-        initial_xml = xml_tmpl.format(addr='9.0.0.1')
+        initial_xml = xml_tmpl.format(addr='9.0.0.1', port='10100')
 
-        target_xml = xml_tmpl.format(addr='9.0.0.12')
+        target_xml = xml_tmpl.format(addr='9.0.0.12', port='10200')
         target_xml = etree.tostring(etree.fromstring(target_xml))
 
         # Preparing mocks
@@ -7935,7 +7948,8 @@ def test_live_migration_update_serial_console_xml(self, mock_xml,
             serial_listen_addr='9.0.0.12',
             target_connect_addr=None,
             bdms=[],
-            block_migration=False)
+            block_migration=False,
+            serial_listen_ports=[10200])
         dom = fakelibvirt.virDomain
         guest = libvirt_guest.Guest(dom)
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)

nova/virt/libvirt/driver.py

@@ -4334,13 +4334,27 @@ def _conf_non_lxc_uml(self, virt_type, guest, root_device_name, rescue,
         else:
             guest.os_boot_dev = blockinfo.get_boot_order(disk_info)
 
-    def _create_consoles(self, virt_type, guest, log_path, flavor, image_meta,
+    def _create_consoles(self, virt_type, guest, instance, flavor, image_meta,
                          caps):
+        log_path = self._get_console_log_path(instance)
         if virt_type in ("qemu", "kvm"):
             # Create the serial console char devices
             guest_arch = libvirt_utils.get_arch(image_meta)
 
             if CONF.serial_console.enabled:
+                try:
+                    # TODO(sahid): the guest param of this method should
+                    # be renamed as guest_cfg then guest_obj to guest.
+                    guest_obj = self._host.get_guest(instance)
+                    if list(self._get_serial_ports_from_guest(guest_obj)):
+                        # Serial port are already configured for instance that
+                        # means we are in a context of migration.
+                        return
+                except exception.InstanceNotFound:
+                    LOG.debug(
+                        "Instance does not exist yet on libvirt, we can "
+                        "safely pass on looking for already defined serial "
+                        "ports in its domain XML", instance=instance)
                 num_ports = hardware.get_number_of_serial_ports(
                     flavor, image_meta)
 
@@ -4540,8 +4554,7 @@ def _get_guest_config(self, instance, network_info, image_meta,
                 flavor, virt_type, self._host)
             guest.add_device(config)
 
-        log_path = self._get_console_log_path(instance)
-        self._create_consoles(virt_type, guest, log_path, flavor,
+        self._create_consoles(virt_type, guest, instance, flavor,
                               image_meta, caps)
 
         pointer = self._get_guest_pointer_model(guest.os_type, image_meta)
@@ -5927,12 +5940,25 @@ def _live_migration_operation(self, context, instance, dest,
                     libvirt.VIR_MIGRATE_TUNNELLED != 0):
                     params.pop('migrate_disks')
 
+            # TODO(sahid): This should be in
+            # post_live_migration_at_source but no way to retrieve
+            # ports acquired on the host for the guest at this
+            # step. Since the domain is going to be removed from
+            # libvird on source host after migration, we backup the
+            # serial ports to release them if all went well.
+            serial_ports = []
+            if CONF.serial_console.enabled:
+                serial_ports = list(self._get_serial_ports_from_guest(guest))
+
             guest.migrate(self._live_migration_uri(dest),
                           migrate_uri=migrate_uri,
                           flags=migration_flags,
                           params=params,
                           domain_xml=new_xml_str,
                           bandwidth=CONF.libvirt.live_migration_bandwidth)
+
+            for hostname, port in serial_ports:
+                serial_console.release_port(host=hostname, port=port)
         except Exception as e:
             with excutils.save_and_reraise_exception():
                 LOG.error(_LE("Live Migration failure: %s"), e,
@@ -6441,6 +6467,13 @@ def rollback_live_migration_at_destination(self, context, instance,
             is_shared_instance_path = True
             if migrate_data:
                 is_shared_instance_path = migrate_data.is_shared_instance_path
+                if (migrate_data.obj_attr_is_set("serial_listen_ports")
+                    and migrate_data.serial_listen_ports):
+                    # Releases serial ports reserved.
+                    for port in migrate_data.serial_listen_ports:
+                        serial_console.release_port(
+                            host=migrate_data.serial_listen_addr, port=port)
+
             if not is_shared_instance_path:
                 instance_dir = libvirt_utils.get_instance_path_at_destination(
                     instance, migrate_data)
@@ -6568,6 +6601,15 @@ def pre_live_migration(self, context, instance, block_device_info,
             CONF.libvirt.live_migration_inbound_addr
         migrate_data.supported_perf_events = self._supported_perf_events
 
+        migrate_data.serial_listen_ports = []
+        if CONF.serial_console.enabled:
+            num_ports = hardware.get_number_of_serial_ports(
+                instance.flavor, instance.image_meta)
+            for port in six.moves.range(num_ports):
+                migrate_data.serial_listen_ports.append(
+                    serial_console.acquire_port(
+                        migrate_data.serial_listen_addr))
+
         for vol in block_device_mapping:
             connection_info = vol['connection_info']
             if connection_info.get('serial'):