nova lacks resource check on compute nodes when doing live migration

[Peterlai]

Bug description:
(1) Keep only one compute node (CN_A) enabled and create instances on CN_A;
(2) After vcpus are fully allocated on CN_A, nova does not allow any instance launched on CN_A;
(3) Enable another compute node (CN_B) and launch an instance (VM_101) on it;
(4) Apply live migration to the instance (VM_101) from CN_B to CN_A successfully; (it means that live migration will not check resources on compute nodes)

[Matt Riedemann (mriedem)]

How are you making the live migration request? Depending on microversion, if you are specifying a target host (CN_A) it can bypass the scheduler which is what you're describing (or if you're using the force parameter with live migration which we just removed in the 2.68 microversion).

More details can be found in the API reference:

https://developer.openstack.org/api-ref/compute/?expanded=live-migrate-server-os-migratelive-action-detail#live-migrate-server-os-migratelive-action

Also, what release are you using?

[Launchpad Janitor (janitor)]

[Expired for OpenStack Compute (nova) because there has been no activity for 60 days.]