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On Mon, Nov 26 2012, Doug Hellmann wrote:

> I understand Julien's reluctance to have the pollsters emitting computed
> data, but tracking values inside the pollster so we can send a delta
> instead of the cumulative value we have now seems like a relatively
> straightforward fix for this.

I may have a better idea.
The problem with doing that in the pollster, is that:
1. it's bad bad bad bad
2. it's inefficient since you may lose values on restart
   you won't know what the value was before
3. it's not sure all publishers targets will want delta

What about doing this with both this approaches:
- with a transformer if someone really wants to do this for a publisher
- for ceilometer-collector, so it inside the collector: it will always
  know what the last value is, since it's stored in the database. So it
  just has to fetch the last stored value from the db if it doesn't know
  it, compute the delta, and stores it.

My main concerns in this, is that it'll be stored as a delta. We'll have
to be clear that polling this kind of things, like delta in general
actually, can't be done multiple times in parrallel. Something that is
easily done -- though maybe not generally wanted -- with cumulative
counters.

Thoughts?

-- 
Julien Danjou
;; Free Software hacker & freelance
;; http://julien.danjou.info
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