> On 4 Apr 2017, at 12:10, Roy Golan <[email protected]> wrote:
>
>
>
> On Tue, Apr 4, 2017 at 12:49 PM Yaniv Kaul <[email protected]
> <mailto:[email protected]>> wrote:
> On Tue, Apr 4, 2017 at 12:29 PM, Roy Golan <[email protected]
> <mailto:[email protected]>> wrote:
> I'm working on a POC lately on a change to stats collection and retrieval by
> VDSM. The moto is to cut all we can from host/vm stats (possibly caps) and
> report only core-business stuff to the engine. Engine will retrieve the rest
> through a 3rd party provider
> (nevermind what is it atm)
I hope it’s the same one as for VM stats, collectd:)
>
> Being backward compatible by design, I have to support 2 API versions for
> Host.getStats , '4.1' and '4.2'.
> Except from supplying less parameters, I want VDSM to do less stuff. It
> doesn't need to sample what it doesn't report. In other words I want
> '4.1-sampling' and '4.2-sampling'
>
> # Introducing 'configuration' Verb:
>
> As engine knows always(Hosted Engine as well) what cluster version this host
> belongs to, it can configure VDSM to operate in cluster version mode.
why not running it in parallel for one version?
>
> Host.configure(config={version: 4.2}
>
> Consider this verb, pre-activating using 'Host.getCaps' to set the context.
> It will set the righjt sampling method, and other stuff if needed then API
> endpoints will have the right permutation of the api to answer it.
>
> 4.2 host can operate in 4.1 mode:
> Host.configure(config={version: 4.1}
>
> Issue: moving a 4.2 host from 4.2 cluster to 4.1 is a problem since engine
> needs to know this is a new vdsm that has the verb available. One way to
> overcome that is to fire the verb for every host regardless of the version
> and disregard an error that implies the verb doesn't exist.
>
> Isn't it solved by host re-installation?
>
> We allow maintenance + change host cluster so not always. Was this changed?
>
>
> # Engine:
> Engine will have a handling of the verb per version.
> Host/Vms monitoring should be changed - I suggest to move out of the
> monitoring code the whole stats collection as it is a different task which is
> orthogonal to 'monitoring' and in 4.2 more than before.
>
>
> I know configuration for VDSM has been discussed before and there are
> probably tons of ways to do it. When you share your thoughts please remember
> that configuration is a by-product of the effort.
>
> How do we persist this level on VDSM? Or we don't, and if VDSM is restarted
> it is again back to 4.1 mode until Engine tells it otherwise?
> Y.
>
> Must persist it somehow otherwise there is a race when the engine will send
> send a stats request and will get the wrong answer. I'm wondering if using
> differnt endpoints is the right solution here to prevent that from happening.
> method: Host.getStats version: 4.1
would it be a problem? assuming that the code is easily started/stopped within
vdsm, we can just change the behavior based on receiving one or the other verb
for the first time after vdsm starts
Thanks,
michal
>
>
>
> Nevertheless it can be potentially beneficial to more functions in vdsm.
>
> Thanks,
> Roy
>
>
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