pcp
[Top] [All Lists]

Re: PCP libvirt PMDA

To: Nathan Scott <nathans@xxxxxxxxxx>
Subject: Re: PCP libvirt PMDA
From: fche@xxxxxxxxxx (Frank Ch. Eigler)
Date: Tue, 19 Jul 2016 20:54:23 -0400
Cc: Marko Myllynen <myllynen@xxxxxxxxxx>, pcp@xxxxxxxxxxx
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <1473242169.7374530.1468971331935.JavaMail.zimbra@xxxxxxxxxx> (Nathan Scott's message of "Tue, 19 Jul 2016 19:35:31 -0400 (EDT)")
References: <1fa58d82-ac73-7747-c58d-acf880bc2155@xxxxxxxxxx> <20ae899d-50c6-1457-644f-f45ad26c63d4@xxxxxxxxxx> <37250089.6949181.1468900166388.JavaMail.zimbra@xxxxxxxxxx> <fc9e92aa-355e-6cc1-7586-599847cf6cbe@xxxxxxxxxx> <1473242169.7374530.1468971331935.JavaMail.zimbra@xxxxxxxxxx>
User-agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux)
Nathan Scott <nathans@xxxxxxxxxx> writes:

> [...]
>> > "libvirt.domstats.net.0.rd.times" - this looks like it's representing
>> > individual network devices using the metric namespace, is that right?
>> [...]
>> > That has proved highly problematic in the past - in general, much more
>> > flexibility (not to mention correctness often, too) [...]

What is an example of the not mentioned "correctness" problems?


>> What kind of "highly problematic" scenarios there has been in the past?
>
> So, one example is pmie - there is no equivalent of some_inst, etc for
> metric names, so rules end up having to be expanded for every metric.

That's true.  And many pm$clients tolerate partially specified pmns
paths, but reject tail constraints:
  pminfo foo
    -> foo.bar.doze foo.bar.joze foo.baz.doze foo.baz.joze 
  pminfo foo.*.doze
    -> no can do
OTOH most of those same clients can't do instance constraints by
regexps or such either.


> Another class of problems is around naming - metric names are defined
> to be less flexible than instance names (as per that pmns(5) extract,
> from earlier).

That is not a problem when the pmns name components are simple
ordinals, like in the present case.


>> I'm also wondering which one would be more easier approach e.g. with
>> pmwebd/grafana or Zabbix?
>
> Not sure it will make a big difference there, except that you have more
> flexibility with naming of instances [...]

In the pmwebd/grafana case, the two scenarios are interchangeable.
Instances appear at the last component of the graphite metric
description, with PMNS names before that.  One could put a
wildcard/glob anywhere.  In this way, it has a more powerful selection
capability than normal pm$clients.


- FChE

<Prev in Thread] Current Thread [Next in Thread>