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On Wed, Nov 7, 2012 at 8:29 AM, Domas Monkus <domas.monkus at canonical.com>wrote:

>  Hello,
> I have found the following wish-list item in the ceilometer project:
> https://bugs.launchpad.net/ceilometer/+bug/1010037
>
> I have read the associated email thread [1] and launchpad blueprint [2],
> however, the task still seems in need of further discussions. To be more
> exact, there are a few things that are still unclear:
>
> 1. How should pollster-specific polling intervals be specified? The
> blueprint mentions that publishers (I assume it means collectors) should
> specify the intervals, however I don't think that a communication channel
> between the collector and the central agent running the pollsters is in
> place.
>

It seems like a configuration file makes the most sense. I don't know if
the openstack.common.cfg module will do what we want for this, or if we
should just use ConfigObj directly.


>
> 2. Should pollsters be able to specify a polling interval (perhaps an
> inherited default) to the central agent?
>

The pollsters shouldn't need to communicate that information to the
collector or central agent.


>
> 3. If other ways of setting the polling intervals are probably possible
> (e.g. the config file), should there be a hierarchy specified of which
> setting override which ones?
>

Having a single way to configure the setting eliminates this issue
entirely, so let's just go with the configuration file.


>
> 4. Should the current periodic_interval configuration value be used as a
> safe fall back for pollsters without explicitly defined values?
>

That makes sense.


>
> 5. What is the granularity of polling intervals? Seconds?
>

That's how the periodic tasks work. I'm not sure if it makes sense to
expose that level of granularity or not. Probably?


>
>
> And finally an implementation idea:
> I do not think that having separate periodic tasks for each pollster is
> the best solution for this problem. Assuming a second granularity for
> polling intervals, the central agent manager can maintain a map of
> pollsters and their intervals. As long as the manager is called with an
> interval that is a GCD of its pollster intervals, it can basically
> calculate how often each pollster should be queried.
>

It could do that. On the other hand, the code that manages the periodic
tasks is *already* doing that. Why rewrite it?

Doug


>
> Domas Monkus
>
> [1] https://lists.launchpad.net/openstack/msg12916.html
> [2]
> https://blueprints.launchpad.net/ceilometer/+spec/publisher-counters-frequency
>
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