only wait for plugtime events in pre-live-migration

This change modifies _get_neutron_events_for_live_migration
to filter the event to just the subset that will be sent
at plug-time.

Currently neuton has a bug where by the dhcp agent
send a network-vif-plugged event during live migration after
we update the port profile with "migrating-to:"
this cause a network-vif-plugged event to be sent for
configuration where vif_plugging in nova/os-vif is a noop.

when that is corrected the current logic in nova cause the migration
to time out as its waiting for an event that will never arrive.

This change filters the set of events we wait for to just the plug
time events.

Related-Bug: #1815989
Closes-Bug: #1901707
Change-Id: Id2d8d72d30075200d2b07b847c4e5568599b0d3b

nova/compute/manager.py

@@ -8055,12 +8055,12 @@ class ComputeManager(manager.Manager):
         LOG.error(msg, msg_args)
 
     @staticmethod
-    def _get_neutron_events_for_live_migration(instance):
+    def _get_neutron_events_for_live_migration(instance, migration):
         # We don't generate events if CONF.vif_plugging_timeout=0
         # meaning that the operator disabled using them.
         if CONF.vif_plugging_timeout:
-            return [('network-vif-plugged', vif['id'])
+            return (instance.get_network_info()
-                    for vif in instance.get_network_info()]
+                    .get_live_migration_plug_time_events())
         else:
             return []
 
@@ -8131,7 +8131,8 @@ class ComputeManager(manager.Manager):
             """
             pass
 
-        events = self._get_neutron_events_for_live_migration(instance)
+        events = self._get_neutron_events_for_live_migration(
+            instance, migration)
         try:
             if ('block_migration' in migrate_data and
                     migrate_data.block_migration):

nova/network/model.py

@@ -469,6 +469,14 @@ class VIF(Model):
         return (self.is_hybrid_plug_enabled() and not
                 migration.is_same_host())
 
+    @property
+    def has_live_migration_plug_time_event(self):
+        """Returns whether this VIF's network-vif-plugged external event will
+        be sent by Neutron at "plugtime" - in other words, as soon as neutron
+        completes configuring the network backend.
+        """
+        return self.is_hybrid_plug_enabled()
+
     def is_hybrid_plug_enabled(self):
         return self['details'].get(VIF_DETAILS_OVS_HYBRID_PLUG, False)
 
@@ -530,15 +538,22 @@ class NetworkInfo(list):
         return jsonutils.dumps(self)
 
     def get_bind_time_events(self, migration):
-        """Returns whether any of our VIFs have "bind-time" events. See
+        """Returns a list of external events for any VIFs that have
-        has_bind_time_event() docstring for more details.
+        "bind-time" events during cold migration.
         """
         return [('network-vif-plugged', vif['id'])
                 for vif in self if vif.has_bind_time_event(migration)]
 
+    def get_live_migration_plug_time_events(self):
+        """Returns a list of external events for any VIFs that have
+        "plug-time" events during live migration.
+        """
+        return [('network-vif-plugged', vif['id'])
+                for vif in self if vif.has_live_migration_plug_time_event]
+
     def get_plug_time_events(self, migration):
-        """Complementary to get_bind_time_events(), any event that does not
+        """Returns a list of external events for any VIFs that have
-        fall in that category is a plug-time event.
+        "plug-time" events during cold migration.
         """
         return [('network-vif-plugged', vif['id'])
                 for vif in self if not vif.has_bind_time_event(migration)]

nova/tests/unit/compute/test_compute_mgr.py

@@ -9256,24 +9256,41 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
         """Tests the various ways that _get_neutron_events_for_live_migration
         will return an empty list.
         """
+        migration = mock.Mock()
+        migration.is_same_host = lambda: False
+        self.assertFalse(migration.is_same_host())
+
         # 1. no timeout
         self.flags(vif_plugging_timeout=0)
 
         with mock.patch.object(self.instance, 'get_network_info') as nw_info:
             nw_info.return_value = network_model.NetworkInfo(
-                [network_model.VIF(uuids.port1)])
+                [network_model.VIF(uuids.port1, details={
+                        network_model.VIF_DETAILS_OVS_HYBRID_PLUG: True})])
+            self.assertTrue(nw_info.return_value[0].is_hybrid_plug_enabled())
             self.assertEqual(
                 [], self.compute._get_neutron_events_for_live_migration(
-                    self.instance))
+                    self.instance, migration))
 
         # 2. no VIFs
         self.flags(vif_plugging_timeout=300)
 
         with mock.patch.object(self.instance, 'get_network_info') as nw_info:
-            nw_info.return_value = []
+            nw_info.return_value = network_model.NetworkInfo([])
             self.assertEqual(
                 [], self.compute._get_neutron_events_for_live_migration(
-                    self.instance))
+                    self.instance, migration))
+
+        # 3. no plug time events
+        with mock.patch.object(self.instance, 'get_network_info') as nw_info:
+            nw_info.return_value = network_model.NetworkInfo(
+                [network_model.VIF(
+                    uuids.port1, details={
+                        network_model.VIF_DETAILS_OVS_HYBRID_PLUG: False})])
+            self.assertFalse(nw_info.return_value[0].is_hybrid_plug_enabled())
+            self.assertEqual(
+                [], self.compute._get_neutron_events_for_live_migration(
+                    self.instance, migration))
 
     @mock.patch('nova.compute.rpcapi.ComputeAPI.pre_live_migration')
     @mock.patch('nova.compute.manager.ComputeManager._post_live_migration')
@@ -9288,9 +9305,11 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
             wait_for_vif_plugged=True)
         mock_get_bdms.return_value = objects.BlockDeviceMappingList(objects=[])
         mock_pre_live_mig.return_value = migrate_data
+        details = {network_model.VIF_DETAILS_OVS_HYBRID_PLUG: True}
         self.instance.info_cache = objects.InstanceInfoCache(
             network_info=network_model.NetworkInfo([
-                network_model.VIF(uuids.port1), network_model.VIF(uuids.port2)
+                network_model.VIF(uuids.port1, details=details),
+                network_model.VIF(uuids.port2, details=details)
             ]))
         self.compute._waiting_live_migrations[self.instance.uuid] = (
             self.migration, mock.MagicMock()
@@ -9320,11 +9339,12 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
         of not waiting.
         """
         migrate_data = objects.LibvirtLiveMigrateData()
+        details = {network_model.VIF_DETAILS_OVS_HYBRID_PLUG: True}
         mock_get_bdms.return_value = objects.BlockDeviceMappingList(objects=[])
         mock_pre_live_mig.return_value = migrate_data
         self.instance.info_cache = objects.InstanceInfoCache(
             network_info=network_model.NetworkInfo([
-                network_model.VIF(uuids.port1)]))
+                network_model.VIF(uuids.port1, details=details)]))
         self.compute._waiting_live_migrations[self.instance.uuid] = (
             self.migration, mock.MagicMock()
         )
@@ -9468,9 +9488,11 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
         mock_get_bdms.return_value = source_bdms
         migrate_data = objects.LibvirtLiveMigrateData(
             wait_for_vif_plugged=True)
+        details = {network_model.VIF_DETAILS_OVS_HYBRID_PLUG: True}
         self.instance.info_cache = objects.InstanceInfoCache(
             network_info=network_model.NetworkInfo([
-                network_model.VIF(uuids.port1), network_model.VIF(uuids.port2)
+                network_model.VIF(uuids.port1, details=details),
+                network_model.VIF(uuids.port2, details=details)
             ]))
         self.compute._waiting_live_migrations = {}
         fake_migration = objects.Migration(