[openstack-dev] [Nova] Ceilometer vs. Nova internal metrics collector for scheduling (was: New DB column or new DB table?)

Sean Dague sean at dague.net
Fri Jul 19 11:04:14 UTC 2013

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 Dague

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