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>From the etherpad [1] (the cross project one):

* This came up with the effort to add a multiattach capability
   filter, at https://review.openstack.org/#/c/645316/1/nova/compute/api.py@1098

* The problem: we want to be able to request allocation candidates
   filtered by a trait that exists on the root provider; but

     * (a) the root provider may provide no resources (eventually -
       e.g. CPU/mem in NUMA providers, shared disk); and/or

         * (My brain hurts from the concept for a provider that
           provides nothing. Perhaps it provides something we aren't
           remembering to count?)

     * (b) we are using only numbered groups and would have to guess
       where to stuff the `required` - again probably based on
       looking for the VCPU/mem resources, which, as above, may wind
       up not on the root provider.

This, basically, is how/when do we deal with resource providers that
have traits but have no classes of inventory of their own (all of it
is on their descendants). The "My brain hurts" comment above is
mine.

The discussion on the review above (good backgrounder for this
thread) had little to do with the immediate need of the proposed
feature. It was a concern about how things will work in the future.
So there are two salient questions (and presumably plenty of other
sidebars):

* How should it work?
* What is the timeline for when it needs to work?

[1] https://etherpad.openstack.org/p/ptg-train-xproj-nova-placement


-- 
Chris Dent                       ٩◔̯◔۶           https://anticdent.org/
freenode: cdent                                         tw: @anticdent