Re: How to monitor domains in regards steal time and other important metrics (VIR_DOMAIN_STATS_VCPU) ?

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Hi Christian,

I can't answer to your question which is too technical for my humble knowledge but I wanted to seize the opportunity to thank you for your effort into maintaining a prometheus exporter for libvirt.

Also I wanted to talk a bit about the features of your exporter, maybe this discussion should be held elsewhere, let me know.

You proposed the prometheus-community to adopt you exporter, which is a super cool idea. But IMHO before that you should have or plan to expose a bit more metrics.

The metric list in the README contains only domain related metrics. Other exporters like tinkoff (the one I'm using) expose a bit more, I know there are metrics about pools at least. Do you plan to include more metrics in the future (volumes, volume pools, networks...)? I can understand if you need only domain related metrics but I think the other metrics should be there if this become a kinda official exporter for libvirt.

Thanks again.

Guy Godfroy

Le 19/01/2024 à 12:35, Christian Rohmann via Users a écrit :
With the holidays and all I take the liberty to bump this post.
Anybody got any idea on how to monitor steal time then?

On 21.12.23 17:36, Christian Rohmann wrote:
Hey libvirt-users,

first allow me to give a little background.

We monitor performance metrics of OpenStack Nova VMs using libvirt as hypervisor. We used to run the libvirt prometheus exporter written by zhangjianweibj [1]. This exporter, compared to the one from kumina / tinkoff ([2]) makes use of the DigitalOcean go-libvirt [3], but that should not make much of a difference for my questions. Since the development of that exporter seems to have stalled and we wanted to rework and contribute new features to it, we created a fork [4]. After working trough the various ideas we had and applying them to the code, we proposed the prometheus-community to adopt the exporter [5] to ensure it is maintained
and to serve as a reference exporter even.

Now to my actual question ...

Libvirt exposes per VCPU stats for domains via [6]. I'd like to be able to export those via the exporter. One important metric to me would be things like the steal time (vcpu.<num>.delay), to determine is domains are starting to get cut short or even starve on cpu time. Apparently those metrics are / cannot be expose anymore since the switch to CGroupsV2? Reading [7] or [8] others seem to have run into this.

Is this actually still the case, even for more recent kernels? If so, I am wondering if there is an issue being tracked to implement this functionality? How is the steal time reported to the guest if the hypervisor is unable to export this info?

Then there are other approaches like vmtop by Digital Ocean [9], which does use info and metrics available via /proc to determine steal time and other vcpu based metrics.
So it seems the required data is somewhat available from the kernel?

Last but not least I'd like your opinion on what other key metrics are important to monitoring on hypervisors and their guests?




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