Re: [Condor-users] Jobs License Management

[Ian Chesal <ICHESAL@xxxxxxxxxx>]

So many questions. I've been waiting for this for...a while! :)

> You can use Concurrency Limits from 7.1.3 [1].

Any idea when we'll see fuller documentation for this feature? I'm most
interested in what happens if a job asks for two limited resources and
another job only asks for one. How are race conditions handled to
minimize blocking? Is there a paper maybe?

> Assign some number of licenses for use by Condor jobs, say
> 300. In your Negotiator's configuration add: MYLICENSE_LIMIT = 300
>
> Now in each job that needs the license add:
> concurrency_limits = MYLICENSE
>
> Condor does not check out the licenses from Flexlm, it just
> tries to keep the number of jobs that /will/ check out
> licenses under control.

Presumably I can write a cron job (startd cron?) on my negotiator that
can update resource counts based on external factors -- is it sufficient
to do a reconfig to have the negotiator see the updated values? What
happens if I decrease a limit and there's more jobs running now than I
say I have resources? Do things preempt? Or does Condor just stop
running jobs that request this resource?

> Especially since you are sharing licenses between batch jobs
> and interactive users you should setup your jobs to notice if
> they failed because they did not checkout a license. This
> configuration will be specific to your application, but the
> document you already mentioned has a good example [2]. If
> your program exits with code 52 when it fails to checkout a
> license you'd add this to your job: on_exit_remove =
> (ExitBySignal == TRUE) || (ExitCode != 52)

Optionally if your license resources supports queuing you can have your
batch jobs wait for a license instead of dying. Depending on how long
things run for and how expensive your licenses are this can be a good
option. For example: if licenses are >> compute hardware it's better to
hold the hardware and queue via the FlexLM manager for the license to
maximize license use than to return to Condor's queue and undergo
another negotiation cycle.

- Ian

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