Comment 2 for bug 1495946

FWIW, I'm changing the tags to match the implementation.

So, that's an expected behaviour, see https://github.com/openstack/nova/blob/875594ad26da46c773892a901511547b86a9568c/nova/scheduler/host_manager.py#L515-L518

When providing a request using the --az hint, it goes into the Compute API where it sets the force_hosts and force_nodes attributes that are passed over the wire to the scheduler and run above
https://github.com/openstack/nova/blob/bc6f30de953303604625e84ad2345cfb595170d2/nova/compute/api.py#L580-L607

I assume the current behaviour is debatable and should be discussed in a spec, that's something I'd love to implement like the same as I provided with http://specs.openstack.org/openstack/nova-specs/specs/liberty/approved/check-destination-on-migrations.html