OVN agent delete support should be backported to pre-wallaby releases

[Terry Wilson]

Until wallaby, ml2/ovn and networking-ovn, despite having support for the Agent API, did not implement "delete" support. This means that when scaling down compute nodes, etc. there are orphaned agents that cannot be removed.

[Terry Wilson (otherwiseguy)]

This is resolved in wallaby by https://review.opendev.org/c/openstack/neutron/+/752795/ which depends on:

https://review.opendev.org/c/openstack/neutron/+/753847/
https://review.opendev.org/c/openstack/neutron/+/754485/
https://review.opendev.org/c/openstack/neutron/+/760967/
https://review.opendev.org/c/openstack/neutron/+/774297/
https://review.opendev.org/c/openstack/neutron/+/774529/
https://review.opendev.org/c/openstack/neutron/+/774298/
https://review.opendev.org/c/openstack/neutron/+/774284/

So it's a fairly significant backport. In addition to adding the missing delete support, the patch also removes 2 sb db writes that get replicated to all connections every agent_down_time/2 seconds that can very negatively impact scaling ml2/ovn.

[Hemanth Nakkina (hemanth-n)]

I dont have free cycles in short term to work on this, so removing myself as assignee.

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

"networking-ovn" project is now unsupported. Closing this bug as "Won't fix".