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.

Conflicts:
    nova/compute/manager.py
    nova/tests/unit/compute/test_compute_mgr.py

Related-Bug: #1815989
Closes-Bug: #1901707
Change-Id: Id2d8d72d30075200d2b07b847c4e5568599b0d3b
(cherry picked from commit 8b33ac064456482158b23c2a2d52f819ebb4c60e)
(cherry picked from commit ef348c4eb3379189f290217c9351157b1ebf0adb)
(cherry picked from commit d9c833d5a404dfa206e08c97543e80cb613b3f0b)

3 files changed, 39 insertions, 9 deletions

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index dbf8308515..ce74fec4c6 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -7154,8 +7154,8 @@ class ComputeManager(manager.Manager):
         # We don't generate events if CONF.vif_plugging_timeout=0
         # meaning that the operator disabled using them.
         if CONF.vif_plugging_timeout and utils.is_neutron():
-            return [('network-vif-plugged', vif['id'])
-                    for vif in instance.get_network_info()]
+            return (instance.get_network_info()
+                    .get_live_migration_plug_time_events())
         else:
             return []
 
diff --git a/nova/network/model.py b/nova/network/model.py
index d8119fae72..7ed9d2d1b8 100644
--- a/nova/network/model.py
+++ b/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
-        has_bind_time_event() docstring for more details.
+        """Returns a list of external events for any VIFs that have
+        "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
-        fall in that category is a plug-time event.
+        """Returns a list of external events for any VIFs that have
+        "plug-time" events during cold migration.
         """
         return [('network-vif-plugged', vif['id'])
                 for vif in self if not vif.has_bind_time_event(migration)]
diff --git a/nova/tests/unit/compute/test_compute_mgr.py b/nova/tests/unit/compute/test_compute_mgr.py
index 93acfee330..526302de8a 100644
--- a/nova/tests/unit/compute/test_compute_mgr.py
+++ b/nova/tests/unit/compute/test_compute_mgr.py
@@ -8831,6 +8831,16 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
         self.flags(vif_plugging_timeout=300, use_neutron=True)
         self.assertEqual(
             [], self.compute._get_neutron_events_for_live_migration([]))
+        # 4. 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))
 
     @mock.patch('nova.compute.rpcapi.ComputeAPI.pre_live_migration')
     @mock.patch('nova.compute.manager.ComputeManager._post_live_migration')
@@ -8845,9 +8855,11 @@ 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()
@@ -8877,11 +8889,12 @@ 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()
         )
@@ -9025,9 +9038,11 @@ 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(