[saga-rg] tasks and jobs...

[Hartmut Kaiser]

Andre Merzky wrote:

I fully support to have the task interface implemented on jobs. An
additional use case for this (apart from what Andre mentioned) would be to
allow to integrate jobs as first class citizens in workflows built out of
saga::task's. 

Regards Hartmut

> 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
>