[collectd] [plugin:virt] - Confusing metrics value type.

Matthias Runge mrunge at matthias-runge.de
Sat Sep 11 15:03:37 CEST 2021

> Am 09.09.2021 um 16:35 schrieb Gaël THEROND <gael.therond at bitswalk.com>:
> Hi everyone,
> I'm currently building some monitoring pages for our Openstack platform.
> To do so I leverage collectd with collectd-virt plugin and write_prometheus
> plugin.
> Everything is fine, I'm receiving all metrics and I'm able to graph them
> from Grafana using prometheus as our datasource.
> The only issue that I'm facing is to manipulate those metrics.
> Our platform is CentOS 8 based and uses Collectd 5.11 provided by CentOS.
> The first issue that I've got is that few metrics labels exposed to
> prometheus aren't listed in here or are having a different name (We do not
> relabeled them yet): https://collectd.org/wiki/index.php/Plugin:virt
> The second issue that I face is to find out the appropriate unit type of
> those metrics as, yes, I've the data type, but are those float and int
> expressing ms? ns? ms/s? time since epoch? or something else?
> Here are the problematic metrics:
> collectd_virt_virt_cpu_total_total - prometheus type counter
> collectd_virt_ps_cputime_user_total - prometheus type counter
> collectd_virt_ps_cputime_syst_total - prometheus type counter


Sorry for not getting back to you sooner.

Since these metrics are total counters, I’d personally look only at differences over time.
Are you using these values for billing purposes, like: your vm used
14533 cpu cycles, that’ll be 43,23 €?

> Subsidiary question:
> Is there any way to get the vm internal memory usage?
> Because within the wiki page there is memory-rss etc but our collectd with
> collectd-virt plugin is just exposing allocated memory.

I would think we are exposing these metrics, but didn’t check lately. In any case, I
See value in having those metrics.
What kind of extrastats config do you use? See https://github.com/collectd/collectd/blob/main/src/collectd.conf.pod#plugin-virt
You can pass the memory option.


> Additional information:
> OS Version: CentOS 8.4.2105
> Kernel: 4.18.0-305.7.1
> Collectd: 5.11.0-2
> Collectd-virt: 5.11.0-2
> Collectd-write_prometheus: 5.11.0-2
> Feel free to tell me if I missed something important.
> Cheers!
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