[RFE] Add new state "ERROR" for HA routers

[Slawek Kaplonski]

Bug originally found by Jakub Libosvar and Assaf Muller:

In the case where a router replica transitions from standby to active (but also in other cases), it might happen that the keepalived-state-change-monitor encounters an error (for example in this case as a result of a permissions issue in /var/lib/neutron), but generally speaking under any error condition, we thought that keepalived-state-change-monitor should update the L3 agent that an error has occurred. Then the L3 agent would put that router replica in 'ERROR' state and update neutron-server, which would update the DB and API responses. This would allow the operator to know that an error happened for that particular router replica and that they should investigate. Bonus points if we also have keepalived-state-change-monitor send the actual error message to the agent. We'd then update the RPC format between the agent and the server and add a DB field like 'error_message' which we could display to the operator.

I'm proposing it as RFE because it would add new state of router on L3 agent and that is user visible change.

[Miguel Lavalle (minsel)]

When you say state, do you mean status?

And the constant already exists: https://opendev.org/openstack/neutron-lib/src/branch/master/neutron_lib/constants.py#L402. Although it seems nobody uses it: http://codesearch.openstack.org/?q=ROUTER_STATUS_ERROR&i=nope&files=&repos=

In any case, it seems sensible to do this. Let's discuss it in the drivers meeting

[Slawek Kaplonski (slaweq)]

Yes, I mean status :)

[Miguel Lavalle (minsel)]

This RFE was approved by the drivers team

[Slawek Kaplonski (slaweq)]

Unfortunately I will not have time to work on this but if anyone wants to work on it, feel free to take it. You can also reach out to me if You would need any more info about it.