[DRMAA-WG] DRMAA2

Thu Jan 13 02:23:17 CST 2011

The newer API specification does look a great deal better, and obviously I
came up with some irrelevant questions.

I'll let you decide what you think about those issues I mentioned that are
still relevant, but first I want to elaborate a little bit about
the job-arrays feature, which is the most crucial feature for us.

When dealing with job arrays, each task actually has two IDs (The ID of the
whole job-array, and the index of the task within the job-array).
Therefore, in job-arrays, all of the queries and actions that are performed
on jobs according to the current DRMAA specification, are actually performed
upon tasks, which are identified by two IDs instead of one, and except of
that are perfectly similar to single jobs.

All I said so far doesn't make any significant difference, and is only a
matter of terminology. But the important thing about job-arrays is the
ability to perform inclusive queries and operations on them.
For example, one can terminate all of the tasks in a job-array using a
single command (supplying only the ID of the whole job-array, without
needing to give the ID of each task, which might be very exhausting for
users).
An example for a more advanced logic that one might want to perform on
job-arrays is to rerun all the failed tasks in a given job-array.
Another advanced logic might be to limit the number of tasks that may run
simultaneously in a job-array (for example, submitting a job-array
containing 1000 tasks, where only 10 tasks are allowed to run simultaneously
at a given time).
The greatest advantage of job-arrays, is the ability of users to "remember"
many tasks with a single ID, what is impossible to do when submitting many
single jobs.

Many schedulers (like LSF) support all these features, and you can see it
implemented in a growing number of scheduler.

We believe that DRMAA should support these features as well, by being more
"job-arrays oriented". I truly believe that DRMAA will be better if it
supports job-arrays.

2011/1/12 Mariusz Mamoński <mamonski at man.poznan.pl>

> Hi Nadav,
>
> On 12 January 2011 17:03, Nadav Brandes <nadavbrandes at gmail.com> wrote:
> > Hello everyone,
> >
> > I went over your API description with my team (as described in
> > http://www.drmaa.org/drmaav2_draft5.pdf).
> please us the wiki as it is the most up to date version of the DRMAA spec:
> http://wikis.sun.com/display/DRMAAv2/Home
> >
> >
> >
> > If it's not too late, we have few questions/suggestions:
> >
> > ·         Can one get a 'Job' object representing a job already submitted
> > once, given only the job index (as an integer)?
> It is supported: The JobSession has a method:
>                sequence<Job> getJobs(JobInfo filter);
> which as i remember is not constrained to jobs submitted via DRMAA.
> >
> > ·         It seems like the 'JobInfo' interface misses few parameters
> given
> > in the 'JobTemplate' interface. For example, can one get the
> 'remoteCommand'
> > of a job that was already submitted, if he only has a 'Job' object in
> hand,
> > and not the 'JobTemplate'?
> >
> > ·         Does DRMAA support job-arrays feature (meaning submitting a
> group
> > of tasks in one job, that has a single ID)? Most schedulers support this
> > feature (include LSF, Moab and SGE). You do have a feature of
> 'runBulkJobs'
> > that sends a sequence of jobs altogether, but it also returns a sequence
> of
> > 'Job' objects, and not a single job with a single ID.
> IMHO most of the batch systems returns many job ids for job arrays but
> they offer to do perform some of the operations on the whole array
> (bulk) by giving common suffix of those job ids. Having one job id,
> thus one Job complicates state model (what if half of the array
> sub-jobs are running and the rest queued? What should be the state of
> the whole array job?)
> >
> > ·         Does DRMAA support the notion of queues (a feature that is
> > supported by all of the schedulers I know)? We believe that it could be
> very
> > useful if one could determine a queue in 'JobTemplate', change the queue
> of
> > an existing job, and also get a list of all the queues in the cluster.
> this was already addressed (wiki!), except alteration of target queue
> of already submitted job.
> >
> > ·         Many batch systems have a feature that allows giving a 'project
> > name' to submitted jobs. We believe that it could also be very useful if
> > 'JobTemplate' had such field.
> has: it is called accountingId
> >
> > ·         Sometimes, especially when dealing with large clusters
> containing
> > a large number of compute nodes (which some of them might be out of
> order),
> > jobs might fail randomly, without any justified reason. We think it could
> be
> > useful if DRMAA supported a feature that allows rerunning failed jobs (as
> > many schedulers allow, like LSF).  Such 'rerun()' method could be added
> to
> > the 'Job' interface.
> We have: rerunnable attribute of the JobTemplate. So one can configure
> batch system to rerun jobs that failed due to resources failure
> >
> > ·         Modern schedulers (like Moab and LSF) support advanced features
> of
> > memory management, cores management, and also general resources
> management
> > (like GPUs). In general, it means giving a list of required resources to
> > each submitted job (for example, submitting a job that requires 5 cores,
> > 12GB RAM, and 2 GPUs). Then the scheduler knows how to schedule the jobs
> so
> > each running job will have all the resources it needs. If 'JobTemplate'
> had
> > a resources dictionary field, it could also be very useful.
> resources that are common for all schedulers are expressed as
> JobTemplate attributes, e.g.: minPhysMemory
> others DRMS specific options (also resources requirements)
>  should go to:          attribute Dictionary drmsSpecific;
>   // must be supported
>
> >
> >
> >
> > This is it for now, thank for reading it.
> thanks for providing your comments, and sorry that you lost much of
> time of reading very old version of the specification (@Peter: maybe
> it would be better to delete reference to the September 2009, DRMAA2
> Draft 5)
> >
> > I would like to hear what you think.
> >
> >
> >
> > Best Regards,
> >
> > Nadav
> >
> > 2010/12/21 Peter Tröger <peter at troeger.eu>
> >>
> >> Hi Navad,
> >>
> >> Now I saw the documentation of the planned interface for DRMAA2, and I
> >> find it to be a great improvement, and very useful for my organization.
> I am
> >> truly anxious to try it, and have some more questions about its release:
> >>
> >> Do you know which distributed resource manager will be the first to
> >> implement DRMAA2? (SGE maybe?) Also, do you have any estimation on when
> >> it'll happen, and when will I be able to download a trial version of it?
> >>
> >> Since we have the Oracle Grid Engine Product Manager as one of the
> >> co-chairs, I leave the implementation estimation to you ;-) .... We also
> >> have very capable people in Poznan, which might take care of non-OGE
> >> systems. We assume to put out the spec in January, and from there, the
> group
> >> can only hope. From experience, I would expect nothing useful before
> Summer
> >> 2011.
> >>
> >> Is it still possible to suggest ideas that we have about the interface
> of
> >> DRMAA2? If so, how is it done? Is it customary to share ideas in this
> forum,
> >> or do you prefer it to be done through Wiki?
> >>
> >> The best thing is to start a discussion on the list. The Wiki is good as
> >> reference. Comments on the Wiki pages might get lost ...
> >> Best regards,
> >> Peter.
> >
> >
> > --
> >  drmaa-wg mailing list
> >  drmaa-wg at ogf.org
> >  http://www.ogf.org/mailman/listinfo/drmaa-wg
> >
>
>
> Best Regards,
> --
> Mariusz
>
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