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On 07/19/13 at 12:08pm, Murray, Paul (HP Cloud Services) wrote:
>Hi Sean,
>
>Do you think the existing static allocators should be migrated to going through ceilometer - or do you see that as different? Ignoring backward compatibility.

It makes sense to keep some things in Nova, in order to handle the 
graceful degradation needed if Ceilometer couldn't be reached.  I see 
the line as something like capabilities should be handled by Nova, 
memory free, vcpus available, etc... and utilization metrics handled by 
Ceilometer.

>
>The reason I ask is I want to extend the static allocators to include a couple more. These plugins are the way I would have done it. Which way do you think that should be done?
>
>Paul.
>
>-----Original Message-----
>From: Sean Dague [mailto:sean at dague.net]
>Sent: 19 July 2013 12:04
>To: OpenStack Development Mailing List
>Subject: Re: [openstack-dev] [Nova] Ceilometer vs. Nova internal metrics collector for scheduling (was: New DB column or new DB table?)
>
>On 07/19/2013 06:18 AM, Day, Phil wrote:
>> Ceilometer is a great project for taking metrics available in Nova and other systems and making them available for use by Operations, Billing, Monitoring, etc - and clearly we should try and avoid having multiple collectors of the same data.
>>
>> But making the Nova scheduler dependent on Ceilometer seems to be the wrong way round to me - scheduling is such a fundamental operation that I want Nova to be self sufficient in this regard.   In particular I don't want the availability of my core compute platform to be constrained by the availability of my (still evolving) monitoring system.
>>
>> If Ceilometer can be fed from the data used by the Nova scheduler then that's a good plus - but not the other way round.
>
>I assume it would gracefully degrade to the existing static allocators if something went wrong. If not, well that would be very bad.
>
>Ceilometer is an integrated project in Havana. Utilization based scheduling would be a new feature. I'm not sure why we think that duplicating the metrics collectors in new code would be less buggy than working with Ceilometer. Nova depends on external projects all the time.
>
>If we have a concern about robustness here, we should be working as an overall project to address that.
>
>	-Sean
>
>--
>Sean Dague
>http://dague.net
>
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