Open Stack

On 11/14/2019 10:09 AM, fsbiz at yahoo.com wrote:
> The requests coming in are "forced host" requests.  The PaaS layer 
> maintains
> an inventory of actual bare-metal available nodes and a user has to 
> explicitly select
> a baremetal node.  The PaaS layer then makes a nova api call for an 
> instance to be created
> on that specific baremetal node.

To be clear, by forced host you mean creating the server with an 
availability zone in the format ZONE:HOST:NODE or ZONE:NODE where NODE 
is the ironic node UUID, correct?

https://docs.openstack.org/nova/latest/admin/availability-zones.html#using-availability-zones-to-select-hosts

Yeah that's a problem because then the scheduler filters aren't run.

A potential alternative is to create the server using a 
hypervisor_hostname query hint that will run through the JsonFilter:

https://docs.openstack.org/nova/latest/admin/configuration/schedulers.html#jsonfilter

Then at least you're not forcing the node and run the scheduler filters.

I forget exactly how the scheduler code works in Queens with respect to 
forced hosts/nodes on server create but the scheduler still has to 
allocate resources in placement. It looks like we work around that in 
Queens by disabling the limit we place on getting allocation candidates 
from placement:

https://review.opendev.org/#/c/584616/

My guess is your PaaS layer has bugs in it since it's allowing users to 
select hosts that are already consumed, or it's just racy. Anyway, this 
is why nova uses placement since Pike for atomic consumption of 
resources during scheduling.

-- 

Thanks,

Matt