[openstack-dev] [nova] I think nova behaves poorly when booting multiple instances

Andrew Laski andrew at lascii.com
Tue Jun 2 20:36:19 UTC 2015

On 06/02/15 at 11:28am, Alexis Lee wrote:
>Andrew Laski said on Mon, Jun 01, 2015 at 09:26:33AM -0400:
>> However what these parameters give users, versus orchestrating
>> outside of Nova, is the ability to have the instances all scheduled
>> as a single block.
>We should seek to provide this via persistent claims. IE add to the
>API something like:
>    claim([ResourceRequest]): [ResourceClaim]
>    boot(ResourceClaim, Image, ...): Instance
>    free_claim([ResourceClaim]): None
>    check_claim([ResourceRequest]): [Boolean]
>(this is not a polished proposal!)
>This allows you to claim() space for many instances, either in one API
>call or across several, before beginning to boot instances. check_claim
>is an obvious extension for probing availability.

There used to be a project that I think was looking for an API like this 
to provide a reservation system, Climate or Blazar or something.  There 
was brief talk of providing something like it for that use case, but the 
idea was put on the backburner to wait for the scheduling rework that's 

The question in my mind is should the claim requests be in the Nova API 
or come from a scheduler API.  And I tend to think that they should come 
from a scheduler API.

>Paul Murray tells me there was a blueprint for this some time ago, but
>I can't find a spec for it. I'm interested in pushing this, I'll put up
>a spec at some point unless someone beats me to it.
>Nova Engineer, HP Cloud.  AKA lealexis, lxsli.
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