post live migration: don't call Neutron needlessly

In bug 1879787, the call to network_api.get_instance_nw_info() in
_post_live_migration() on the source compute manager eventually calls
out to the Neutron REST API. If this fails, the exception is
unhandled, and the migrating instance - which is fully running on the
destination at this point - will never be updated in the database.
This update normally happens later in
post_live_migration_at_destination().

The network_info variable obtained from get_instance_nw_info() is used
for two things: notifications - which aren't critical - and unplugging
the instance's vifs on the source - which is very important!

It turns out that at the time of the get_instance_nw_info() call, the
network info in the instance info cache is still valid for unplugging
the source vifs. The port bindings on the destination are only
activated by the network_api.migrate_instance_start() [1] call that
happens shortly *after* the problematic get_instance_nw_info() call.
In other words, get_instance_nw_info() will always return the source
ports. Because of that, we can replace it with a call to
instance.get_network_info().

[1] d9e04c4ff0/nova/network/neutronv2/api.py (L2493-L2522)

Change-Id: If0fbae33ce2af198188c91638afef939256c2556
Closes-bug: 1879787
(cherry picked from commit 6488a5dfb2)
(cherry picked from commit 2c949cb3ee)
(cherry picked from commit 7ace26e4bc)
This commit is contained in:
Artom Lifshitz 2020-08-21 13:06:58 -04:00
parent a50fb46df8
commit 703c8ef4e6
3 changed files with 18 additions and 5 deletions

View File

@ -7106,7 +7106,13 @@ class ComputeManager(manager.Manager):
# Releasing vlan.
# (not necessary in current implementation?)
network_info = self.network_api.get_instance_nw_info(ctxt, instance)
# NOTE(artom) At this point in time we have not bound the ports to the
# destination host yet (this happens in migrate_instance_start()
# below). Therefore, the "old" source network info that's still in the
# instance info cache is safe to use here, since it'll be used below
# during driver.post_live_migration_at_source() to unplug the VIFs on
# the source.
network_info = instance.get_network_info()
self._notify_about_instance_usage(ctxt, instance,
"live_migration._post.start",

View File

@ -6553,8 +6553,9 @@ class ComputeTestCase(BaseTestCase,
mock.patch.object(
self.compute.network_api, 'setup_networks_on_host'),
mock.patch.object(migration_obj, 'save'),
mock.patch.object(instance, 'get_network_info', return_value=[]),
) as (
mock_migrate, mock_setup, mock_mig_save
mock_migrate, mock_setup, mock_mig_save, mock_get_nw_info
):
self.compute._post_live_migration(c, instance, dest,
migrate_data=migrate_data,
@ -6566,6 +6567,7 @@ class ComputeTestCase(BaseTestCase,
mock_migrate.assert_called_once_with(c, instance, migration)
mock_post.assert_called_once_with(c, instance, False, dest)
mock_clear.assert_called_once_with(mock.ANY)
mock_get_nw_info.assert_called()
@mock.patch('nova.compute.utils.notify_about_instance_action')
def test_post_live_migration_working_correctly(self, mock_notify):
@ -6608,12 +6610,15 @@ class ComputeTestCase(BaseTestCase,
'clear_events_for_instance'),
mock.patch.object(self.compute, 'update_available_resource'),
mock.patch.object(migration_obj, 'save'),
mock.patch.object(instance, 'get_network_info'),
) as (
post_live_migration, unfilter_instance,
migrate_instance_start, post_live_migration_at_destination,
post_live_migration_at_source, setup_networks_on_host,
clear_events, update_available_resource, mig_save
clear_events, update_available_resource, mig_save, get_nw_info,
):
nw_info = network_model.NetworkInfo.hydrate([])
get_nw_info.return_value = nw_info
self.compute._post_live_migration(c, instance, dest,
migrate_data=migrate_data,
source_bdms=bdms)
@ -6636,7 +6641,7 @@ class ComputeTestCase(BaseTestCase,
post_live_migration_at_destination.assert_has_calls([
mock.call(c, instance, False, dest)])
post_live_migration_at_source.assert_has_calls(
[mock.call(c, instance, [])])
[mock.call(c, instance, nw_info)])
clear_events.assert_called_once_with(instance)
update_available_resource.assert_has_calls([mock.call(c)])
self.assertEqual('completed', migration_obj.status)

View File

@ -8702,6 +8702,7 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
source_node='src')
image_bdm.attachment_id = uuids.attachment3
@mock.patch.object(instance, 'get_network_info')
@mock.patch('nova.compute.utils.notify_about_instance_action')
@mock.patch('nova.objects.ConsoleAuthToken.'
'clean_console_auths_for_instance')
@ -8720,7 +8721,7 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
def _test(mock_net_api, mock_notify, mock_driver,
mock_rpc, mock_get_bdm_info, mock_attach_delete,
mock_update_resource, mock_bdm_save, mock_ga,
mock_clean, mock_notify_action):
mock_clean, mock_notify_action, mock_get_nw_info):
self._mock_rt()
bdms = objects.BlockDeviceMappingList(objects=[vol_bdm, image_bdm])
@ -8737,6 +8738,7 @@ class ComputeManagerMigrationTestCase(test.NoDBTestCase,
mock.call(self.context, instance, 'fake-mini',
action='live_migration_post', phase='end')])
self.assertEqual(2, mock_notify_action.call_count)
mock_get_nw_info.assert_called()
_test()