Comment 10 for bug 1790569

Which release are you using? Since Queens conductor should move the allocations for the source node held by the instance to the migration record, and then the scheduler will claim resources on the dest node using the instance consumer record. If the scheduler fails to reply to the call from conductor, the conductor task should cleanup the allocations in the rollback routine:

https://github.com/openstack/nova/blob/stable/queens/nova/conductor/tasks/migrate.py#L318

https://github.com/openstack/nova/blob/stable/queens/nova/conductor/tasks/live_migrate.py#L129

Are you using Queens or newer and not seeing that happen? Or is the RPC cast from conductor to the compute methods failing somehow and we're not properly rolling back?