----- Original Message -----
>
> kenj wrote:
>
> > [...] Depending on the overhead of this instrumentation, you may
> > wish to consider using an additional control variable and pmStore(1)
> > to allow a user to enable or disable the collection [...]
>
> FWIW, I wish we leaned less on this particular technique.
The missing piece is better (client) tool support - its needed for not
just enabling expensive metrics, but also server-side filtering. It'd
be neat for pmchart to offer this kind of capability, as well as the
many console tools.
> The pmda
> infrastructure has the ability to track individual pcp clients coming
> and going.
> So, a pmda can/should activate collection on demand,
A client simply showing interest in the metrics from a PMDA is not enough
information to know whether expensive collection should be enabled or not
though. A PMDA can export both expensive and inexpensive metrics too, or
the enabled state may be system wide (like hardware counters, or gluster
volume stats, or any of a number of other things that the underlying data
domain creators have chosen not to enable by default).
cheers.
--
Nathan
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