[openstack-dev] [ceilometer] Counter frequency bp discussion

Eoghan Glynn eglynn at redhat.com
Mon Jan 7 15:19:11 UTC 2013

> Hi, Doug
> 	As a follow--up with you on the counter frequency discussion, I
> 	create a wiki page at
> 	http://wiki.openstack.org/Ceilometer/blueprints/publisher-counters-frequency
> 	. Please have a look on it.

Some initial thoughts ...

"The pollster will decide the polling interval based on the GCD
of interval requirement for all of it's counters."

Would it make sense to factor out from the pollsters this common
logic to calculate the period GCD?

Also, should we constrain the possible periods to avoid lots of
irregularity (e.g. just allow 1s, 10s, 60s & multiples thereof),
or make it completely free form?

"... the compute/central service will create a timer for each
pollster based on it's polling interval"

Do we need a separate timer for each pollster, even when the periods
are common?

"A interval transformer provided to support different
interval. Considering followed counters sequence as "c0, c1, c2,
c3 ..." for resource_1 and c3 happens "interval time" after c0."

Is the implicatyion here that *all* counters associated with a
pollster are calculated on the most granular interval, then the
more coarse-grained values are eventually discarded in the
transformer chain?

That would be fine if only a single measurement (e.g. call out
to a public API service or hypervisor daemon) is required for
all the pollster's counters. But if multiple measurements are
required, would it make sense to avoid the measure-and-discard


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