[openstack-dev] [Nova] Ceilometer vs. Nova internal metrics collector for scheduling

Sandy Walsh sandy.walsh at rackspace.com
Fri Jul 19 18:11:12 UTC 2013

On 07/19/2013 12:30 PM, Sean Dague wrote:
> On 07/19/2013 10:37 AM, Murray, Paul (HP Cloud Services) wrote:
>> If we agree that "something like capabilities" should go through Nova,
>> what do you suggest should be done with the change that sparked this
>> debate: https://review.openstack.org/#/c/35760/
>> I would be happy to use it or a modified version.
> CPU sys, user, idle, iowait time isn't capabilities though. That's a
> dynamically changing value. I also think the current approach where this
> is point in time sampling, because we only keep a single value, is going
> to cause some oddly pathologic behavior if you try to use it as
> scheduling criteria.
> I'd really appreciate the views of more nova core folks on this thread,
> as it looks like these blueprints have seen pretty minimal code review
> at this point. H3 isn't that far away, and there is a lot of high
> priority things ahead of this, and only so much coffee and review time
> in a day.

You really need to have a moving window average of these meters in order
to have anything sensible. Also, some sort of view into the pipeline of
scheduler requests (what's coming up?)

Capabilities are only really used in the host filtering phase. The host
weighing phase is where these measurements would be applied.

>     -Sean

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