openstack team mailing list archive

[Doug Hellmann <doug.hellmann@xxxxxxxxxxxxx>]

On Tue, May 29, 2012 at 1:10 PM, Matt Joyce <matt.joyce@xxxxxxxxxxxxxxxx>wrote:

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


The collector should record everything and we should make the query API
work so the caller can get what they want out of the datastore.


>
>
> On Tue, May 29, 2012 at 9:30 AM, Loic Dachary <loic@xxxxxxxxxxxx> 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@xxxxxxxxxxxx  ☎ +33 1 49 70 99 82
>>
>>
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