Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/validate-targethost-live-migration.

Description:


This is related to blueprint https://blueprints.launchpad.net/openstack/?searchtext=live-migration-to-conductor. The blueprint is trying to move live migration logic to nova-conductor, this is a good direction.

But for live migration with target host, the current implementation is that once target host was specified for live migration, then the conductor will only validate the host by nova compute. For some cases, there is also a need to validate the host in nova scheduler, as there might be some requirement that customer want to validate the target host for live migration with some scheduler filters.

In the current implementation the user can specify scheduler hints related to the placement of the instance. Those scheduler hints are used when the instance run for the first time and they are ignored afterwards. In order to achieve the validation of the target host we need to persist scheduler hints into the database which makes it possible to verify that the target host passes scheduler filters/hints during live migration.

There are some cases when this verification during live migration will lead the system locked and the user will not be able to migrate an instance, so a new option should be added in order to force the migration without verifying the target host by nova-scheduler.

Specification URL (additional information):

None