Hi Brian,
The FRONT_END_MODE is designed for any system where the slurmd does
not execute on the compute node, for example IBM BlueGene or Cray
systems running ALPS. Since the slurmd does not execute on the compute
nodes, an alternate task launch plugin is required. The launch/runjob
plugin is used for IBM BlueGene/Q systems and launch/aprun for Cray
systems, which cause srun to invoke IBM's runjob command or Cray's
aprun command after translating options appropriately. If you are
using a custom application to launch tasks then a new launch plugin is
probably your best option.
The FRONT_END_MODE is also used for testing purposes. For that purpose
we let the srun command launch tasks, but only as user SlurmUser or
root. Without this restriction, user could easily cause the slurmd to
directly launch thousands of tasks and quite possibly exceed resources
limits and cause the slurmd daemon to fail. If you want to disable
this check for user SlurmUser or root then comment out the code in
src/slurmctld/proc_req.c around line 1688:
#if defined HAVE_FRONT_END && !defined HAVE_BGQ && !defined HAVE_CRAY
/* Limited job step support */
/* Non-super users not permitted to run job steps on front-end.
* A single slurmd can not handle a heavy load. */
if (!validate_slurm_user(uid)) {
info("Attempt to execute job step by uid=%d", uid);
slurm_send_rc_msg(msg, ESLURM_NO_STEPS);
return;
}
#endif
Moe
Quoting Brian Gilmer <[email protected]>:
>
> I am trying to build a cluster with Slurm 2.5 using front end mode for
> single node serial jobs. I have compute nodes that are only connected
> via a PCI so I need to use a custom application to launch jobs. I am
> not able to launch jobs using srun either at the command prompt or via
> a batch file. I get: "srun error: Unable to create job step: Job
> steps can not be run on this cluster" or "srun: error: srun task
> launch not supported on this system". I am able to get jobs to launch
> if I use the custom application in a batch file. I am also able to
> get the jobs to launch with srun as root. Looking at the code this is
> all consistent. What I don't quite understand is how is
> front-end-mode supposed to be used given the restrictions.
>
> It would be helpful to get some background on the application of
> front-end-mode. I am also wondering with the new launch plugin if the
> restriction on front-end-mode still apply.
>
> Thanks
> Brian F Gilmer
> BCT-LLC
>
>
>
> --
> Speak when you are angry--and you will make the best speech you'll
> ever regret.
> - Laurence J. Peter
