[openstack-dev] [nova][ironic] Concerns over rigid resource class-only ironic scheduling

Jay Pipes jaypipes at gmail.com
Thu Oct 19 14:38:01 UTC 2017

On 10/16/2017 05:31 AM, Nisha Agarwal wrote:
> Hi Matt,
> As i understand John's spec https://review.openstack.org/#/c/507052/ 
> <https://review.openstack.org/#/c/507052/>, it is actually a replacement 
> for capabilities(qualitative only) for ironic. It doesnt cover the 
> quantitative capabilities as 'traits' are meant only for qualitative 
> capabilities. Quantitative capabilities are covered by resource classes 
> in Nova. We have few (one or two) quantitative capabilities already 
> supported in ironic.

Hi Nisha,

This may be a case of mixed terminology. We do not refer to anything 
quantitative as a "capability". Rather, we use the term "resource class" 
(or sometimes just "resource") to represent quantitative things that may 
be consumed by the instance.

Traits, on the other hand, are qualitative. They represent a binary 
on/off capability that the compute host (or baremetal node in the case 
of Ironic) exposes.

There's no limit on the number of traits that may be associated with a 
particular Ironic baremetal node. However, for Ironic baremetal nodes, 
if the node.resource_class attribute is set, the Nova Ironic virt driver 
will create a single inventory record for the node containing a quantity 
of 1 and a resource class equal to whatever is in the 
node.resource_class attribute. This resource class is auto-created by 
Nova as a custom resource class.


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