[Buildbot-devel] scheduler questions

[Stefan Seefeld]

Brian Warner wrote:
>>Reading the manual I stumble upon the 'Nightly' scheduler, and find the
>>following note:
>>
>>
>>"note that this Scheduler only lets you control the time between builds,
>>not the absolute time-of-day of each Build..."
> 
> 
> That part of the manual needs to be clarified.. the Nightly scheduler class
> will indeed do the crontab-style scheduling that you want to do.

Ok, found it. (On the master I'm still running 0.7.1, so I'll switch once
I can upgrade.)

>>On a related note, is there anything I can do to control the level of
>>concurrency, i.e. the number of processes run in parallel on a given
>>machine (e.g. slave) ? It would be good to be able to constrain the number
>>of builds executed in parallel on a particular machine, to avoid excessive
>>high loads.
> 
> 
> We have slave-wide Locks, which can keep the number of processes down to one
> per slave. With a little bit of work, these could probably be enhanced to
> behave more like multiple-holder semaphores, so you could have two or three
> Steps or Builds running at the same time on any given slave.

Yes, I think that would be very useful indeed.

> The manual has a section on Locks with some examples.. take a look at ones
> that use the SlaveLock class.
> 
> You could also conceivably create a Scheduler that was somehow aware of the
> load on the slave machines, and avoided triggering a build that would be run
> on a very busy slave. This would somewhat violate the current separation
> between Scheduler, Builder, and buildslave, however.

Right, but it sounds like a worthwhile paradigm shift. Instead of hardcoding
the assignment of builders to slaves, one would express 'can-run' relationships,
and then let the buildmaster manage assignments.

Regards,
		Stefan