[neutron] missing dhcp ports after reboot and neutron-ovs-cleanup

Slawek Kaplonski skaplons at redhat.com
Thu Dec 16 21:04:01 UTC 2021


On czwartek, 16 grudnia 2021 21:05:18 CET Kamil Madáč wrote:
> Hello
> We have deployed Victoria release with kolla-ansible (openvswitch neutron
> driver), and after the reboot of control nodes we are experiencing issues
> with dhcp on some networks. I found out that there were missing dhcp tap
> interfaces in br-int openvswitch. After restart of dhcp agetn and
> openvswitch agent, interface was added to br-int and dhcp works again in
> that network. I found bug from 2016
> (https://bugs.launchpad.net/kolla/+bug/1617188), that there is a script
> neutron-ovs-cleanup (it is in each neutron docker container), which should
> be run after reboot of dhcp/L3 nodes otherwise issues with dhcp/metadata/l3
> functionalities could arise.

Basically what this script is doing is the same for both L3 and DHCP agents as 
both of them are plugging things into br-int in the same way. 

> I do not see mentioned this in kolla documentation, bug is quite old and
> expired, so I would like to ask, is that still valid and should it be run
> manually after each reboot of dhcp/L3 node? If yes, what is best what how to
> achieve it when docker starts all container automatically after reboot.
> Should I stop neutron containers, run neutron-ovs-cleanup and start them
> again?

You must be sure that this script runs (if runs) before agents (and nova-
compute) will start. The reason for that is that this script is pretty dummy 
and will simply remove everything from the br-int and other e.g. physical 
So if You will have some race between e.g. this script and DHCP agents, it may 
happen that dhcp agent will already create tap ports for some networks and 
then this script will remove them.

> Kamil Madáč
> Slovensko IT a.s.

Slawek Kaplonski
Principal Software Engineer
Red Hat
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