Comment 4 for bug 1813224

For this particular case, I found this error:

2019-01-24 19:01:33.969 9 ERROR vif_plug_ovs.ovsdb.impl_vsctl [req-9ba4d327-4bad-4a45-99c1-9dcf22b37193 f14d275e92cb4384ba0502ca1738c8cc 3879640c10fe4962a8ca60cd0be8dbd9 - default default] Unable to execute ['ovs-vsctl', '--timeout=120', '--oneline', '--format=json', '--', '--may-exist', 'add-br', u'br-int', '--', 'set', 'Bridge', u'br-int', u'datapath_type=system']. Exception: Unexpected error while running command.
Command: ovs-vsctl --timeout=120 --oneline --format=json -- --may-exist add-br br-int -- set Bridge br-int datapath_type=system
Exit code: 1
Stdout: u''
Stderr: u'ovs-vsctl: unix:/var/run/openvswitch/db.sock: database connection failed (No such file or directory)\n': ProcessExecutionError: Unexpected error while running command.
2019-01-24 19:01:33.995 9 ERROR vif_plug_ovs.ovsdb.impl_vsctl [req-9ba4d327-4bad-4a45-99c1-9dcf22b37193 f14d275e92cb4384ba0502ca1738c8cc 3879640c10fe4962a8ca60cd0be8dbd9 - default default] Unable to execute ['ovs-vsctl', '--timeout=120', '--oneline', '--format=json', '--', '--may-exist', 'add-port', u'br-int', u'qvo94387b07-f4', '--', 'set', 'Interface', u'qvo94387b07-f4', u'external_ids:iface-id=94387b07-f47c-4529-a398-4e09a6f7c7ce', 'external_ids:iface-status=active', u'external_ids:vm-uuid=67d0ffd8-13ca-4271-9eeb-fd16ae96bbad', u'external_ids:attached-mac=fa:16:3e:9e:cb:9f']. Exception: Unexpected error while running command.
Command: ovs-vsctl --timeout=120 --oneline --format=json -- --may-exist add-port br-int qvo94387b07-f4 -- set Interface qvo94387b07-f4 external_ids:iface-id=94387b07-f47c-4529-a398-4e09a6f7c7ce external_ids:iface-status=active external_ids:vm-uuid=67d0ffd8-13ca-4271-9eeb-fd16ae96bbad external_ids:attached-mac=fa:16:3e:9e:cb:9f
Exit code: 1
Stdout: u''
Stderr: u'ovs-vsctl: unix:/var/run/openvswitch/db.sock: database connection failed (No such file or directory)\n': ProcessExecutionError: Unexpected error while running command.

http://logs.openstack.org/31/626631/11/check/tripleo-ci-fedora-28-standalone/cf314a4/logs/undercloud/var/log/containers/nova/nova-compute.log.txt.gz#_2019-01-24_19_01_33_969

Checking other jobs, I also found this:

2019-01-27 20:05:04.762 9 ERROR vif_plug_ovs.ovsdb.impl_vsctl [req-c0565eb3-be73-4d2a-b59e-a7cc37f759d5 c9745094b10545779ae32bf53dd8cca9 7afb8674582846bc82865e1a71d6e67c - default default] Unable to execute ['ovs-vsctl', '--timeout=120', '--oneline', '--format=json', '--', '--may-exist', 'add-port', u'br-int', u'qvo1a3b80e5-55', '--', 'set', 'Interface', u'qvo1a3b80e5-55', u'external_ids:iface-id=1a3b80e5-5521-4134-bad5-3841ec13eead', 'external_ids:iface-status=active', u'external_ids:vm-uuid=4d420cb6-dc79-48d6-9df3-2d7041f8ca05', u'external_ids:attached-mac=fa:16:3e:78:78:8f']. Exception: Unexpected error while running command.
Command: ovs-vsctl --timeout=120 --oneline --format=json -- --may-exist add-port br-int qvo1a3b80e5-55 -- set Interface qvo1a3b80e5-55 external_ids:iface-id=1a3b80e5-5521-4134-bad5-3841ec13eead external_ids:iface-status=active external_ids:vm-uuid=4d420cb6-dc79-48d6-9df3-2d7041f8ca05 external_ids:attached-mac=fa:16:3e:78:78:8f
Exit code: -14
Stdout: u''
Stderr: u'2019-01-27T20:05:04Z|00002|fatal_signal|WARN|terminating with signal 14 (Alarm clock)\n': ProcessExecutionError: Unexpected error while running command.

http://logs.openstack.org/39/633039/2/check/tripleo-ci-fedora-28-standalone/6455149/logs/undercloud/var/log/containers/nova/nova-compute.log.txt.gz#_2019-01-27_20_05_04_762

Although the errors are different, both are related to ovs-vsctl