[drmaa-wg] Synchronizing Against Waited Jobs

[Rajic, Hrabri]

My wig is in dry cleaning.  Nevertheless, here is my short take on this.


If an implementation has handy job_id's it could conveniently make good
determination which jobs are invalid (do not exist) and throw
DRMAA_ERRNO_INVALID_JOB.   IMHO, it is not a big deal if the routine
gives imprecise diagnostics if it is forced to do memory garbage
collection earlier.  Quality of implementation term comes to mind, but
that quality could come at the expense of being memory hog that in turn
could lead to paging - quite dubious. 
See, the implementations might differently handle jobs that did not come
from the current session, so we could not be precise here either.

The important thing for the user is to synchronize i.e. block program
from continuing if there are running remote jobs.  
  
Dispose = true helps get rid of the rusage info to free DRMAA
implementations of heavy memory requirements when it matters, so keeping
all the past job_ids for providing precise exit errors runs contrary to
the goal of lessening memory requirements in the same routine.

My 2 pfennigs,

Hrabri

>-----Original Message-----
>From: owner-drmaa-wg at ggf.org [mailto:owner-drmaa-wg at ggf.org] On Behalf
Of
>Daniel Templeton
>Sent: Wednesday, October 19, 2005 11:37 AM
>To: DRMAA Working Group
>Subject: [drmaa-wg] Synchronizing Against Waited Jobs
>
>We have found a bug in the SGE DRMAA implementation, (I know! It's
>shocking!) but Andreas and I can't agree on what the fix should be.
The
>issue is that in the current implementation, synchronizing against jobs
>that did not come from the current session returns DRMAA_ERRNO_SUCCESS.
>The part about which we disagree is what should happen when
>synchronizing against jobs that are from the current session, but that
>have already ended and have already had drmaa_wait() (or
>drmaa_synchronize() with dispose=true) called against them.
>
>My stance is that one can extrapolate from the drmaa_wait() function
>that there is no difference between jobs which don't exist (at all or
in
>the current session) and jobs whose exit information has been disposed
>(via drmaa_wait() or drmaa_synchronize()).  Therefore, calling
>drmaa_synchronize() on jobs which have already had drmaa_wait() called
>against them should return DRMAA_ERRNO_INVALID_JOB.
>
>Andreas holds that it can be inferred from the lack of the above
>statement in the spec, that drmaa_synchronize() handles such jobs
>differently from drmaa_wait().  Because drmaa_synchronize() does not
>need the jobs' exit information to succeed, it should be able to
operate
>on jobs whose exit information has already been disposed.  Therefore,
>calling drmaa_synchronize() on jobs which have already had drmaa_wait()
>called against them should return DRMAA_ERRNO_SUCCESS.
>
>I can agree that Andreas' position makes theoretical sense, but I
>believe it runs contrary to the stated goal of minimizing the
>requirements on the implementing DRMS.  In order to implement a
>drmaa_synchronize() that can distinguish between job's that have been
>disposed and jobs that never existed, the DRMAA implementation must
keep
>a list of the ids of every job that has ever been submitted in the
>current session, and with every drmaa_synchronize() call, the list must
>be searched to validate the synchronize id list.  And for what?
>DRMAA_JOB_IDS_ALL covers every case I can think of where the behavior
>Andreas described would be useful. To me, it sounds like a lot of extra
>work for the DRMAA implementation with no tangible benefit.
>
>On what Andreas and I can agree is that if we decide he is right, we
>will close the bug as "won't fix" because the fix will be worse than
the
>bug.  In any case, we should probably have a tracker item to make the
>final decision explicit in the spec.
>
>What say you, oh, wise ones?
>
>Daniel
>
>--
>***************************************************
>*        Daniel Templeton   ERGB01 x60220         *
>*       Staff Engineer, Sun N1 Grid Engine        *
>***************************************************
>* "So let the sunshine in.  Face it with a grin.  *
>*  Smilers never lose, and frowners never win."   *
>*      -Let the Sunshine In, Pebbles Flintstone   *
>***************************************************
>