[saga-rg] tasks and jobs...

[Andre Merzky]

Hiho, 

I can't remember exactly where the sugegstion came from, but
here it is anyway.

Wouldn't it be useful to have jobs implementing the task
interface?

Well, the advatages would be:

  - you can put jobs into tak containers, and wait() for
    them to change state/finish

  - if we have notification on tasks (see earlier mail from
    November or so), we have now notification on jobs as
    well, w/o the need to introduce a new mechanism

  - it seems simple to map the job states to task states:
    Done       -> DoneOK
    Failed     -> DoneFail
    all others -> Running

    (as a side note, we should consider have the same names
    for Done and Failed...)

The only difference I see in terms of semantic is that tasks
can be Pending - i.e. not yet started.  Jobs can't, as soon
as you create them, they are at least Queued.

However, that is a topic I wated to open anyway:
One of our earliest use cases is bulk job submission (from
Hrabri/DRMAA).  The current API does not allow to implement
that use case efficiently - the only possibility is:

  for ( int i = 0; i < 1.000.000; i++ )
  {
    my_jobs[i] = job_server.submit_job (job_description[i]);
  }


Having jobs more task like would help:

  for ( int i = 0; i < 1.000.000; i++ )
  {
    task_container.add_task (job_server.create_job (job_description[i]));
  }

  task_container.run ();
  

The semantics would be now:

  job = job_server.create_job (job_description); 
  // job is pending now

  job.run ();
  // job is queued now, or whatever - see previous mail.


That argumentation is very similar to the one we hade about
task creation: there we have:

  task t1 = file.read <async> (...); // t1 is running
  task t2 = file.read <task>  (...); // t2 is pending

  t2.run (); // t2 is running


same for jobs then:

  job j1 = job_server.submit_job <async> (...); // t1 is running
  job j2 = job_server.create_job <task>  (...); // t2 is pending

  j2.run (); // j2 is running



Feedback as always would be very welcome.  An issue in that
respect is in the issue list (since a couple of weeks
actually).


Best regards, 

  Andre.


-- 
"So much time, so little to do..."  -- Garfield
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