Revert resize: wait for events according to hybrid plug

Since 4817165, when reverting a
resized instance back to the source host, the libvirt driver waits for
vif-plugged events when spawning the instance. When called from
finish_revert_resize() in the source compute manager, libvirt's
finish_revert_migration() does not pass vifs_already_plugged to
_create_domain_and_network(), making the latter use the default False
value.

When the source compute manager calls
network_api.migrate_instance_finish() in finish_revert_resize(), this
updates the port binding back to the source host. If Neutron is
configured to use OVS hybrid plug, it will send the vif-plugged event
immediately after completing this request. This happens before the
virt driver's finish_revert_migration() method is called. This causes
the wait in the libvirt driver to time out because the event is
received before Nova starts waiting for it.

The neutron ovs l2 agent sends vif-plugged events when two conditions
are met. First the port must be bound to the host managed by the
l2 agent and second, the agent must have completed configuring the
port on ovs. This involves assigning the port a local VLAN for tenant
isolation, applying security group rules if required and applying
QoS policies or other agent extensions like service function chaining.

During the boot process, we bind the port first to the host
then plug the interface into ovs which triggers the l2 agent to
configure it resulting in the emission of the vif-plugged event.
In the revert case, as noted above, since the vif is already plugged
on the source node when hybrid-plug is used, binding the port to the
source node fulfils the second condition to send the vif-plugged event.

Events sent immediately after port binding update are hereafter known
as "bind-time" events. For ports that do not use OVS hybrid plug,
Neutron will continue to send vif-plugged events only when Nova
actually plugs the VIF. These types of events are hereafter known as
"plug-time" events. OVS hybrid plug is a per agent setting, so for
a particular host, bind-time events are an all-or-nothing thing for the
ovs backend: either all VIF_TYPE=ovs ports have them, or no ovs ports
have them. In general, a host will only have one network backend.
The only exception to this is SR-IOV. SR-IOV is commonly deployed on
the same host as other network backends such as OVS or linuxbridge.
SR-IOV ports with VNIC_TYPE=direct-physical will always have only
bind-time events. If an instance mixes OVS ports with hybrid-plug=False
with direct physical ports, it will have both kinds of events.

This patch adds functions to the NetworkInfo model that return what
kinds of events each VIF has. These are then used in the migration
revert logic to decide when to wait for external events: in the
compute manager, when binding the port, for bind-time events,
and/or in libvirt, when plugging the VIFs, for plug-time events.

Closes-bug: 1832028
Co-Authored-By: Sean Mooney [email protected]
Change-Id: I51cdcae67be8c68a55bc939de4ea0aba2361dcc4

Author: notartom

nova/compute/manager.py

@@ -4164,6 +4164,50 @@ def revert_resize(self, context, instance, migration):
             self.compute_rpcapi.finish_revert_resize(context, instance,
                     migration, migration.source_compute)
 
+    def _finish_revert_resize_network_migrate_finish(self, context, instance,
+                                                     migration):
+        """Causes port binding to be updated. In some Neutron or port
+        configurations - see NetworkModel.get_bind_time_events() - we
+        expect the vif-plugged event from Neutron immediately and wait for it.
+        The rest of the time, the event is expected further along in the
+        virt driver, so we don't wait here.
+
+        :param context: The request context.
+        :param instance: The instance undergoing the revert resize.
+        :param migration: The Migration object of the resize being reverted.
+        :raises: eventlet.timeout.Timeout or
+                 exception.VirtualInterfacePlugException.
+        """
+        network_info = instance.get_network_info()
+        events = []
+        deadline = CONF.vif_plugging_timeout
+        if deadline and utils.is_neutron() and network_info:
+            events = network_info.get_bind_time_events()
+            if events:
+                LOG.debug('Will wait for bind-time events: %s', events,
+                          instance=instance)
+        error_cb = self._neutron_failed_migration_callback
+        try:
+            with self.virtapi.wait_for_instance_event(instance, events,
+                                                      deadline=deadline,
+                                                      error_callback=error_cb):
+                # NOTE(hanrong): we need to change migration.dest_compute to
+                # source host temporarily.
+                # "network_api.migrate_instance_finish" will setup the network
+                # for the instance on the destination host. For revert resize,
+                # the instance will back to the source host, the setup of the
+                # network for instance should be on the source host. So set the
+                # migration.dest_compute to source host at here.
+                with utils.temporary_mutation(
+                        migration, dest_compute=migration.source_compute):
+                    self.network_api.migrate_instance_finish(context,
+                                                             instance,
+                                                             migration)
+        except eventlet.timeout.Timeout:
+            with excutils.save_and_reraise_exception():
+                LOG.error('Timeout waiting for Neutron events: %s', events,
+                          instance=instance)
+
     @wrap_exception()
     @reverts_task_state
     @wrap_instance_event(prefix='compute')
@@ -4211,17 +4255,8 @@ def finish_revert_resize(self, context, instance, migration):
 
             self.network_api.setup_networks_on_host(context, instance,
                                                     migration.source_compute)
-            # NOTE(hanrong): we need to change migration.dest_compute to
-            # source host temporarily. "network_api.migrate_instance_finish"
-            # will setup the network for the instance on the destination host.
-            # For revert resize, the instance will back to the source host, the
-            # setup of the network for instance should be on the source host.
-            # So set the migration.dest_compute to source host at here.
-            with utils.temporary_mutation(
-                    migration, dest_compute=migration.source_compute):
-                self.network_api.migrate_instance_finish(context,
-                                                         instance,
-                                                         migration)
+            self._finish_revert_resize_network_migrate_finish(
+                context, instance, migration)
             network_info = self.network_api.get_instance_nw_info(context,
                                                                  instance)
 
@@ -6439,8 +6474,8 @@ def pre_live_migration(self, context, instance, block_migration, disk,
         return migrate_data
 
     @staticmethod
-    def _neutron_failed_live_migration_callback(event_name, instance):
-        msg = ('Neutron reported failure during live migration '
+    def _neutron_failed_migration_callback(event_name, instance):
+        msg = ('Neutron reported failure during migration '
                'with %(event)s for instance %(uuid)s')
         msg_args = {'event': event_name, 'uuid': instance.uuid}
         if CONF.vif_plugging_is_fatal:
@@ -6518,7 +6553,7 @@ class _BreakWaitForInstanceEvent(Exception):
                 disk = None
 
             deadline = CONF.vif_plugging_timeout
-            error_cb = self._neutron_failed_live_migration_callback
+            error_cb = self._neutron_failed_migration_callback
             # In order to avoid a race with the vif plugging that the virt
             # driver does on the destination host, we register our events
             # to wait for before calling pre_live_migration. Then if the

nova/network/model.py

@@ -458,6 +458,16 @@ def labeled_ips(self):
                     'ips': ips}
         return []
 
+    def has_bind_time_event(self):
+        """When updating the port binding to a host that already has the
+        instance in a shutoff state (in practice, this currently means
+        reverting a resize or cold migration), the following Neutron/port
+        configurations cause network-vif-plugged events to be sent as soon as
+        the binding is updated:
+        - OVS with hybrid plug
+        """
+        return self.is_hybrid_plug_enabled()
+
     def is_hybrid_plug_enabled(self):
         return self['details'].get(VIF_DETAILS_OVS_HYBRID_PLUG, False)
 
@@ -515,6 +525,24 @@ def wait(self, do_raise=True):
     def json(self):
         return jsonutils.dumps(self)
 
+    def get_bind_time_events(self):
+        """When updating the port binding to a host that already has the
+        instance in a shutoff state (in practice, this currently means
+        reverting a resize or cold migration), return external events that are
+        sent as soon as the binding is updated.
+        """
+        return [('network-vif-plugged', vif['id'])
+                for vif in self if vif.has_bind_time_event()]
+
+    def get_plug_time_events(self):
+        """When updating the port binding to a host that already has the
+        instance in a shutoff state (in practice, this currently means
+        reverting a resize or cold migration), return external events that are
+        sent when the VIF is plugged.
+        """
+        return [('network-vif-plugged', vif['id'])
+                for vif in self if not vif.has_bind_time_event()]
+
 
 class NetworkInfoAsyncWrapper(NetworkInfo):
     """Wrapper around NetworkInfo that allows retrieving NetworkInfo

nova/tests/unit/compute/test_compute.py

@@ -5891,7 +5891,9 @@ def fake_finish_revert_migration_driver(*args, **kwargs):
             old_vm_state = vm_states.ACTIVE
         else:
             old_vm_state = vm_states.STOPPED
-        params = {'vm_state': old_vm_state}
+        params = {'vm_state': old_vm_state,
+                  'info_cache': objects.InstanceInfoCache(
+                      network_info=network_model.NetworkInfo([]))}
         instance = self._create_fake_instance_obj(params)
 
         self.stub_out('nova.virt.fake.FakeDriver.finish_migration', fake)
@@ -6041,7 +6043,9 @@ def test_finish_revert_resize_validate_source_compute(self):
         def fake(*args, **kwargs):
             pass
 
-        instance = self._create_fake_instance_obj()
+        params = {'info_cache': objects.InstanceInfoCache(
+                      network_info=network_model.NetworkInfo([]))}
+        instance = self._create_fake_instance_obj(params)
 
         self.stub_out('nova.virt.fake.FakeDriver.finish_migration', fake)
         self.stub_out('nova.virt.fake.FakeDriver.finish_revert_migration',

nova/tests/unit/compute/test_compute_mgr.py

@@ -5054,6 +5054,81 @@ def test_notify_volume_usage_detach_no_block_stats(self):
                     self.context, fake_instance, fake_bdm)
         block_stats.assert_called_once_with(fake_instance, 'vda')
 
+    def _test_finish_revert_resize_network_migrate_finish(self, vifs, events):
+        instance = fake_instance.fake_instance_obj(self.context)
+        instance.info_cache = objects.InstanceInfoCache(
+            network_info=network_model.NetworkInfo(vifs))
+        migration = objects.Migration(
+            source_compute='fake-source',
+            dest_compute='fake-dest')
+
+        def fake_migrate_instance_finish(context, instance, migration):
+            self.assertEqual(migration.source_compute, 'fake-source')
+            # NOTE(artom) This looks weird, but it's checking that the
+            # temporaty_mutation() context manager did its job.
+            self.assertEqual(migration.dest_compute, 'fake-source')
+
+        with test.nested(
+            mock.patch.object(self.compute.virtapi,
+                              'wait_for_instance_event'),
+            mock.patch.object(self.compute.network_api,
+                              'migrate_instance_finish',
+                              side_effect=fake_migrate_instance_finish)
+        ) as (mock_wait, mock_migrate_instance_finish):
+            self.compute._finish_revert_resize_network_migrate_finish(
+                self.context, instance, migration)
+            mock_wait.assert_called_once_with(
+                instance, events, deadline=CONF.vif_plugging_timeout,
+                error_callback=self.compute._neutron_failed_migration_callback)
+            mock_migrate_instance_finish.assert_called_once_with(
+                self.context, instance, migration)
+
+    def test_finish_revert_resize_network_migrate_finish_wait(self):
+        """Test that we wait for bind-time events if we have a hybrid-plugged
+        VIF.
+        """
+        self._test_finish_revert_resize_network_migrate_finish(
+            [network_model.VIF(id=uuids.hybrid_vif,
+                               details={'ovs_hybrid_plug': True}),
+             network_model.VIF(id=uuids.normal_vif,
+                               details={'ovs_hybrid_plug': False})],
+            [('network-vif-plugged', uuids.hybrid_vif)])
+
+    def test_finish_revert_resize_network_migrate_finish_dont_wait(self):
+        """Test that we're not waiting for any events if we don't have any
+        hybrid-plugged VIFs.
+        """
+        self._test_finish_revert_resize_network_migrate_finish(
+            [network_model.VIF(id=uuids.hybrid_vif,
+                               details={'ovs_hybrid_plug': False}),
+             network_model.VIF(id=uuids.normal_vif,
+                               details={'ovs_hybrid_plug': False})],
+            [])
+
+    def test_finish_revert_resize_network_migrate_finish_no_vif_timeout(self):
+        """Test that we're not waiting for any events if vif_plugging_timeout
+        is 0.
+        """
+        self.flags(vif_plugging_timeout=0)
+        self._test_finish_revert_resize_network_migrate_finish(
+            [network_model.VIF(id=uuids.hybrid_vif,
+                               details={'ovs_hybrid_plug': True}),
+             network_model.VIF(id=uuids.normal_vif,
+                               details={'ovs_hybrid_plug': True})],
+            [])
+
+    @mock.patch.object(utils, 'is_neutron', return_value=False)
+    def test_finish_revert_resize_network_migrate_finish_not_neutron(self, _):
+        """Test that we're not waiting for any events if we're not using
+        Neutron.
+        """
+        self._test_finish_revert_resize_network_migrate_finish(
+            [network_model.VIF(id=uuids.hybrid_vif,
+                               details={'ovs_hybrid_plug': True}),
+             network_model.VIF(id=uuids.normal_vif,
+                               details={'ovs_hybrid_plug': True})],
+            [])
+
 
 class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
     def setUp(self):

nova/tests/unit/network/test_network_info.py

@@ -15,6 +15,7 @@
 #    under the License.
 
 from oslo_config import cfg
+from oslo_utils.fixture import uuidsentinel as uuids
 
 from nova import exception
 from nova.network import model
@@ -857,6 +858,21 @@ def test_injection_ipv6_with_lxc_no_gateway(self):
                 libvirt_virt_type='lxc')
         self.assertEqual(expected, template)
 
+    def test_get_events(self):
+        network_info = model.NetworkInfo([
+            model.VIF(
+                id=uuids.hybrid_vif,
+                details={'ovs_hybrid_plug': True}),
+            model.VIF(
+                id=uuids.normal_vif,
+                details={'ovs_hybrid_plug': False})])
+        self.assertEqual(
+            [('network-vif-plugged', uuids.hybrid_vif)],
+            network_info.get_bind_time_events())
+        self.assertEqual(
+            [('network-vif-plugged', uuids.normal_vif)],
+            network_info.get_plug_time_events())
+
 
 class TestNetworkMetadata(test.NoDBTestCase):
     def setUp(self):