[DRMAA-WG] DRMAA2
Peter Tröger
peter at troeger.eu
Tue Jan 25 01:31:16 CST 2011
Hi Nadav,
> (1) I agree that putting an option to filter jobs with any generic user-made filter would be pretty horrible, and it's already better just to let him iterate over the jobs himself and filter them has he likes. But I would put a feature that allows filtering jobs in certain status (as many batch systems support). Something like this:
>
> Interface JobArray {
>
> …
>
> Sequence<Job> getJobsOfState(in JobState state)
>
I can understand the practical usefulness, but this falls into a category of functions we typically reject. First, it has a timing issue - what happens if an already identified job changes its state before the collected result is returned ? Second, it has not automatically a consistent mapping to DRM-specific interfaces, since the job model is DRMAA-specific. There might be DRMAA-states that do not exist in the particular system. There might be also DRMAA states not specific enough, the ones that only map to some DRMS state together with a sub state.
Since this function is easily implementable with both manual looping or the new event callback features, I would prefer to reject it - as long as we don't have more enthusiastic feedback for other DRM systems. DRMAA tries to stay minimalistic, and this one gives you only a small performance advantage, but no real functional advantage.
> (2) Also, I think that DRMAA should allow giving job-arrays more arguments that what regular jobs can get (in JobTemplate struct). For example, as I mentioned before, you might want to give a 'slotsLimit' argument to a new submitted job-array (in order to limit the number of tasks in the job-array that may run simultaneously). Therefore, I would change the interface to something like this:
>
> struct JobArrayTemplate extends JobTemplate {
>
> // Contains all the attributes that JobTemplate contains
>
> // Also contains the following attributes:
>
> attribute long beginIndex
>
> attribute long endIndex
>
> attribute long step
>
> attribute long slotsLimit; // In order to limit the number of tasks in the job-array that may run at any one time
>
> // I guess that more attributes will be added here over-time
>
> }
>
Job templates are intended for re-usage, so I don't know if it makes sense to have to index attributes in the template.
For slots in general, we had long and painful discussions. We were able to agree that slots are an opaque concept to DRMAA, since there is absolutely no common mapping in the different DRM systems. Talking about a slots limit for jobs gives them semantics, which we cannot do. Sorry, but this on is a candidate for the still-existing native options.
> By the way, you can see that all the features that I mentioned here are supported by LSF:
>
> http://www-cecpv.u-strasbg.fr/Documentations/lsf/html/lsf6.1_admin/G_jobarrays.html#26618
>
Great, it is very good to have an LSF guy in the group. I would be happy if you could also do some sanity check for the existing concepts with respect to LSF.
Since we good no heavy objection against my JobArray proposal, I will add it to the spec draft.
> On Sat, Jan 15, 2011 at 12:34 AM, Andre Merzky <andre at merzky.net> wrote:
> Hi Peter,
>
> in your proposal below, I am missing the waitAllStarted /
> waitAllTerminated versions (which would return void IMHO). Otherwise
> looks great to me. waitAll is easily implementable in the library
> (max cost: 2n*waitAny).
Thanks Andre, but WaitAll* functions are not part of the spec at all, so they will also not be part of JobArray. Same argumentation as above. Since waitAll() is so easy to implement, there is no reason to clutter up the DRMAA interface with it.
Best,
Peter.
>
> My $0.02,
>
> Andre.
>
>
> On Fri, Jan 14, 2011 at 10:36 PM, Peter Tröger <peter at troeger.eu> wrote:
> >
> > ==== snip ===
> > interface JobSession {
> > ...
> > Job runJob(in DRMAA::JobTemplate jobTemplate)
> > JobArray runBulkJobs(in DRMAA::JobTemplate jobTemplate, in
> > long beginIndex, in long endIndex, in long step)
> > ...
> > }
> > interface JobArray {
> > readonly attribute string jobArrayId;
> > sequence<Job> jobs;
> > readonly attribute JobSession session;
> > readonly attribute JobTemplate jobTemplate;
> > readonly attribute Reservation reservation;
> > void suspend() // suspend all jobs of the array, partial failures in
> > changing the state are ok
> > void resume() // resume all jobs of the array, partial failures in
> > changing the state are ok
> > void hold() // put a queued bulk job on hold
> > void release() // release an array job on hold
> > void terminate() // terminate a running job
> > Job waitAnyStarted(in TimeAmount timeout) // similar to JobSession function
> > Job waitAnyTerminated(in TimeAmount timeout) // similar to JobSession
> > function
> > };
> > ==== snip ===
> > Fetching status information makes only sense on job level, so the according
> > getInfo() call is not part of the JobArray interface.
> > I would also resist the temptation to add a JobArray counterpart of
> > getJobs(JobInfo filter), since the filter semantics would become horrible to
> > specify.
> > All functions should be implementable with the 'loop' fallback in the
> > library, when we allow partial success in the bulk control functions.
> > DRMAA folks, your comments please. Is this a feasible interface for the
> > denoted DRM systems with direct job array control support ?
> > Best,
> > Peter.
> >
> >
> >
> >
> > Am 13.01.2011 um 09:23 schrieb Nadav Brandes:
> >
> > 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
> >
> > --
> > drmaa-wg mailing list
> > drmaa-wg at ogf.org
> > http://www.ogf.org/mailman/listinfo/drmaa-wg
> >
> > --
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> >
>
>
>
> --
> Nothing is ever easy...
>
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