[users at bb.net] Migrating to Nine and our capability system

[Georges Racinet]

On 03/23/2016 01:07 PM, Pierre Tardy wrote:
>
>
> Le mar. 22 mars 2016 à 22:07, Georges Racinet <gracinet at anybox.fr
> <mailto:gracinet at anybox.fr>> a écrit :
>
>     Hi there,
>
>     After a long time during which we couldn't do much more than
>     maintaining
>     our instances, we (Anybox) are considering migrating our buildbots
>     to Nine.
>
>
> This is good news!
>  
>
>
>     Among the many things that I've developed for our needs [1], there
>     is a
>     rather complete capability system [3], and hence I must decide whereas
>     it's worth porting it or not [4]. I know it's a fairly common need
>     that many
>     development shops have been doing in private or almost, but it's not
>     obvious to me what is freely available (for Nine) on this topic.
>
>     http://trac.buildbot.net/ticket/3120 does not get to a conclusion,
>     and I
>     couldn't find much on it in a quick search of recent messages on this
>     list. Maybe I missed something else ?
>
>
> Since that, I figured Workers have properties, which can be used in
> NextSlave callback in order to match any capability.
> I think it would be much better to have something in the core, not
> depending on having the users writing a capability specific
> nextSlave/nextBuild callbacks.
>
> Actually, there are two aspect in the capability problem. The static
> and the dynamic.
>
> 1\ Static problem is the easiest. It looks this is what you
> implemented already (and metabuildbot has in a smaller extend):
> - One part of your config describe the workers, and their capabilities
> - Another part is describing the builders, and their required capability.
> The system will then automatically configure which worker to associate
> to which builders.
Yes, that is exactly what I'm doing. It's a bit more actually, since our
system also spawns builder variants (applying the same BuildFactory
several times for different versions of some capabilities).
 
The full capability description is stored as a dict-valued Worker
property, something you may very well call a hack.
Then at build time, a custom step extracts the needed properties for
that build. This is good enough for us, but it is intrusive : the step
must be introduced in the build sequence.
>
> 2\ The dynamic problem. Slave are chosen at the start build phase.
> - One part of your config describe the workers, and their capabilities
> - Another part is describing the builders, and their required capability.
> - Each build requests can require an additional set of capabilities,
> which can restrict more the set of slaves which can run them.
> In order to implement that efficiently, one will have to mess around
> inside the buildrequest distributor code, which I can understand looks
> scary.
I just took a quick tour of that for an unrelated reason
(http://trac.buildbot.net/ticket/3498), yes it's a bit convoluted.

>
> I am not sure which one you are needing/implementing.
> I think it is fine that you only implement 1/ if this is what you
> need, but I would like that the design opens the door to implementing
> 2 without need to rewrite everything.
Interesting. I think I didn't know about nextWorker at the time I
started this. What concrete use-case do you have in mind for 2/  ?
Also, if the idea is that users don't need to implement 
nextWorker/nextBuild, then it means they may implement it for other
purposes, and it follows that the dynamic dispatching must play nice
with that, isn't it ?

Regards,

-- 
Georges Racinet
Anybox SAS, http://anybox.fr
Téléphone: +33 6 51 32 07 27
GPG: 0x33AB0A35, sur serveurs publics

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