Open Stack

On 31/08/2015 3:36 PM, Julien Danjou wrote:
> On Mon, Aug 31 2015, gord chung wrote:
>
>> i'm not sure Gnocchi is where we should be fixing this as it really only
>> (potentially) fixes it for Gnocchi and not for any of the other ways Ceilometer
>> data can be consumed.
> The ideal way is to send the data as it is collected and do the
> treatment in the backend, otherwise you end up implementing the world in
> Ceilometer.

but if it's not actually cumulative in Ceilometer (pre-storage), should 
we really be tagging it as such?

>> a proposed solution in bug and in a previous thread suggests that a 'delta'
>> meter be built from cputime value libvirt provides which would better handle
>> the reset scenario. that said, is there another option to truly have a
>> cumulative meter?
> Yes, the hackish way might be to convert those cumulative to delta with
> a transfomer in the pipeline and be done with it. Though you'll probably
> have data points missing on restart, which is not ultimate solution. As
> soon as you start losing information in the Ceilometer pipeline by
> transforming I'll stand and say "bad idea". :-)

so i was thinking rather than modify the existing meter, we build a new 
cpu.delta meter, which is gives the delta. it seems like giving a delta 
meter would make the behaviour more consistent.

>
> So yes, you have to have a smart storage solution in the end.
>
ideally, i was thinking Nova would capture this data and there would be 
absolutely no data loss as Nova knows exactly when instances are 
restarted/stopped... that said, it's arguably outside the scope of Nova.

cheers,

-- 
gord