Hey nova team, Some context: I want nova-scheduler to favor instances on some computes based on some hypervisor metrics/traits. E.G. I have 2 hypervisors hosting few instances. One of them is having an old kernel, that I will upgrade some day. The second is already having the correct target kernel. I want the scheduler to favor booting on the second host (good kernel). How can I achieve that without disabling the bad_kernel hypervisor? I was thinking about something in the weight scheduler. I was first thinking about using placement traits (having a custom traits) and reading traits from a weight scheduler. But it seems not doable out of the box. And it also seems not a good idea at all to call placement API from weight scheduler. Maybe I am missing something here because I was expecting to have the traits given by placement up to the nova scheduler. Second shoot, I found the metrics weight [1] which rely on the compute monitors. It seems less hacky, but I will still have to write custom monitor to retrieve such metrics. Am I missing an option here? Is there anyone doing such thing is the community? [1] https://github.com/openstack/nova/blob/master/nova/scheduler/weights/metrics... [2] https://github.com/openstack/nova/tree/master/nova/compute/monitors Cheers, Arnaud.