Failed to start OVN cause of sock file nonexisted

[Eric Xie]

Use latest source of devstack, the git log as below:
commit 591e15a3dcc89b44f31604dda41c4f332767c380 (HEAD -> master, origin/master, origin/HEAD)
Merge: e102559f b1a89eb8
Author: Zuul <email address hidden>
Date: Tue Aug 31 20:47:21 2021 +0000

    Merge "Configure access to physical network also with ML2/OVN backend"

Deploy it on ubuntu 18.04.5
# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.5 LTS
Release: 18.04
Codename: bionic

Got error:
+lib/neutron_plugins/ovn_agent:wait_for_sock_file:174 die 174 'Socket /var/run/openvswitch/ovnnb_db.sock not found'
+functions-common:die:198 local exitcode=0
+functions-common:die:199 set +o xtrace
[Call Trace]
devstack/stack.sh:1286:start_ovn_services
/opt/stack/devstack/lib/neutron-legacy:477:start_ovn
/opt/stack/devstack/lib/neutron_plugins/ovn_agent:692:wait_for_sock_file
/opt/stack/devstack/lib/neutron_plugins/ovn_agent:174:die
[ERROR] /opt/stack/devstack/lib/neutron_plugins/ovn_agent:174 Socket /var/run/openvswitch/ovnnb_db.sock not found
Error on exit

The path of sock file is located at /run/ovn/.

The ovn version:
# dpkg -l | grep -i ovn
ii ovn-central 20.03.2-0ubuntu0.20.04.1~cloud0 amd64 OVN central components
ii ovn-common 20.03.2-0ubuntu0.20.04.1~cloud0 amd64 OVN common components
ii ovn-controller-vtep 20.03.2-0ubuntu0.20.04.1~cloud0 amd64 OVN vtep controller
ii ovn-host 20.03.2-0ubuntu0.20.04.1~cloud0 amd64 OVN host components

[jay (jay763190097)]

same error:
```
+lib/neutron_plugins/ovn_agent:wait_for_sock_file:170 '[' '!' -S /var/run/openvswitch/ovnnb_db.sock ']'
+lib/neutron_plugins/ovn_agent:wait_for_sock_file:171 sleep 1
+lib/neutron_plugins/ovn_agent:wait_for_sock_file:172 count=6
+lib/neutron_plugins/ovn_agent:wait_for_sock_file:173 '[' 6 -gt 5 ']'
+lib/neutron_plugins/ovn_agent:wait_for_sock_file:174 die 174 'Socket /var/run/openvswitch/ovnnb_db.sock not found'
+functions-common:die:253 local exitcode=0
+functions-common:die:254 set +o xtrace
[Call Trace]
./stack.sh:1264:start_ovn_services
/opt/stack/devstack/lib/neutron-legacy:498:start_ovn
/opt/stack/devstack/lib/neutron_plugins/ovn_agent:692:wait_for_sock_file
/opt/stack/devstack/lib/neutron_plugins/ovn_agent:174:die
[ERROR] /opt/stack/devstack/lib/neutron_plugins/ovn_agent:174 Socket /var/run/openvswitch/ovnnb_db.sock not found
Error on exit
World dumping... see /opt/stack/logs/worlddump-2021-11-23-144913.txt for details

```

need help......

[Dr. Jens Harbott (j-harbott)]

This error likely has been fixed, it was due to a race condition sometimes being triggered when restart the network services. If you still see this issue, please create a new bug with fresh logs.

[melanie witt (melwitt)]

New bug opened at https://bugs.launchpad.net/devstack/+bug/1980421