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On Wed, Nov 28 2012, Eoghan Glynn wrote:

A quick answer, I think Eoghan wrote what I would have written if I had
been faster to reply. :)

>> 	Also I envision the CW data will be stored in the storage, with a
>> 	dimensions table, and CW data in another table. Each
>> 	(metricname+dimensions) combination will have an entry on the
>> 	dimension table. A table for the alarm, and alarm table will be
>> 	updated when new data added.
>
> Yes, I would expect that it would involve some different data structures in
> the store.
>
> In fact it could well be a completely different store (e.g. a metric store
> based on Cassandra, while the metering store defaults to Mongo).

Yes, the point is that this is not really a Ceilometer concern as Eoghan
says. The CW publisher pushes in another software, that's it. :)

>> 	With this envision, the translation from Counter to CW data will
>> 	happen in publisher
>
> In the transformer, not the publisher, I would have thought.

Yes, in the transformers (plural probably).

>>       and we may need various type of transformer to
>> 	achieve it, including a) Unit translation like from kb to byte, b)
>> 	interval translation like from 10s to 60s,
>
> I don't think we need interval translation. The metric is just pushed to
> CW when it becomes available. The push doesn't involve specifying a period.
> Instead the period (e.g. 60s) is specified when the metric is queried. If
> the polling interval was set to 10s, then a GetMetricStatistics call with
> period=60s would result in aggregation over the ~6 datapoints per period.

Yeah, not sure interval translation is the role of any transformer
indeed. It's more the "scheduler" job to honor publisher requirements
about events interval they want.

>> 	However, if we will achieve CW data from API side (that also make
>> 	sense and seems more flexible), then I don't think any transformer
>> 	needed, except the CPU utilization, which has been implemented
>> 	already. The interval in fact does not matter in such situation,
>> 	except the interval of the pollster.
>
> Well it depends on whether the CW service in integral to ceilo, or at
> arms length. In the latter case, e.g. Synaps, the CW publisher would do
> the metric push via the CW public API.

Yep, for now we don't envisage doing CW inside Ceilo. If Ceilometer API
can do that at some point for an almost free cost, we'll see. For now
it's not in our scope.

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