[nova] Strict isolation of group of hosts for image and flavor, modifying command 'nova-manage placement sync_aggregates'

Eric Fried openstack at fried.cc
Mon Jun 10 22:38:36 UTC 2019

>>> (e) Fully manual. Aggregate operations never touch (add or remove)
>>> traits on host RPs. You always have to do that manually.

I'm going to come down in favor of this option. It's the shortest path
to getting something viable working, in a way that is simple to
understand, despite lacking magical DWIM-ness.

>>> As noted above,
>>> it's easy to do - and we could make it easier with a tiny wrapper that
>>> takes an aggregate, a list of traits, and an --add/--remove command. So
>>> initially, setting up aggregate isolation is a two-step process, and in
>>> the future we can consider making new API/CLI affordance that combines
>>> the steps.
> ya e could work too.
> melanie added a similar functionality to osc placment for managing the alloction ratios
> of specific resource classes per aggregate a few months ago 
> https://review.opendev.org/#/c/640898/
> we could proably provide somthing similar for managing traits but determining what RP to
> add the trait too would be a littel tricker. we would have to be able to filter to RP with either a
> specific inventory or with a specific trait or in a speicic subtree.

We (Placement team) are still trying to figure out how to manage
concepts like "resourceless request groups" and "traits/aggregates flow
down". But for now, Nova is still always modeling VCPU/MEMORY_MB and
traits on the root provider, so let's simply hit the providers in the
aggregate (i.e. the root compute host RPs).

I'm putting this on the agenda for Thursday's nova meeting [1] to
hopefully get some more Nova opinions on it.


[1] https://wiki.openstack.org/wiki/Meetings/Nova#Agenda_for_next_meeting

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