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Do we want a history of deltas or just last delta and leave the history to
UI implementers?

On Tue, May 29, 2012 at 9:30 AM, Loic Dachary <loic at enovance.com> wrote:

> On 05/29/2012 05:42 PM, Doug Hellmann wrote:
> > IIRC, the meters discussed in the wiki [1] are supposed to show "delta"
> values (usage since the last time an event was generated), although the
> "Alternate Gauge Design" section discusses cumulative meters instead. The
> libvirt pollsters we have now produce cumulative data, and it might be
> complicated and error-prone to change them to compute the deltas internally
> before generating events. On the other hand, some of the other counters may
> be more complicated to generate as cumulative values.
> >
> > Rather than taking an either/or approach, I propose we document for each
> counter whether it uses the delta or cumulative approach. The API server
> can ask the meter plugin for that piece of information when calculating the
> aggregate value so that the caller does not have to keep track of the rules
> for each meter.
> >
> I tend to prefer using a gauge and I agree that documenting what was
> preferred (gauge or delta) for a given meter / counter is enough.
>
> My 2ct ;-)
>
> --
> Loïc Dachary         Chief Research Officer
> // eNovance labs   http://labs.enovance.com
> // ✉ loic at enovance.com  ☎ +33 1 49 70 99 82
>
>
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