Open Stack

Hi folks!

If you're not aware already, I'm working on solving "node is locked" 
problems breaking users (and tracking it at 
https://etherpad.openstack.org/p/ironic-locking-reform). We have retries 
in place in client, but we all agree that it's not the eventual solution.

One of the things we've figured out is that we actually have server-side 
retries - in task_manager.acquire. They're nice and configurable. Alas, 
we have one place that checks reservations without task_manager: 
https://github.com/openstack/ironic/blob/master/ironic/api/controllers/v1/node.py#L401-L403 
(note that this check is actually racy)

I'd like to ask your opinions on how to solve it? I have 3 ideas:
1. Just implement retries on API level (possibly split away a common 
function from task_manager).
2. Move update to conductor instead of doing it directly in API.
3. Don't check reservation when updating node. At all.

Ideas?