Jobs at regular intervals

If you have small tasks you want to run at regular intervals, Slurm has the scrontab utility available. It gives you a cron-like interface for submitting and running batch jobs at regular intervals, e.g. monitoring tasks or housekeeping scripts.

Usage

Like cron, Slurm uses a configuration file to define these recurring jobs. Each users has it's own configuartion file. The files are not edited dierctly, but instead you can use scrontab -e to edit 1) your all your scrontab-jobs.

Inside the scrontab file, you can use #SCRON to give instructions to the scheduler, similar to the #SBATCH lines in normal jobscript, though not all options are supported. After the #SCRON lines, you have one line to define when and what should be done, just like a normal cron job.

You have two styles of defining when you job should run:

  1. common time intervals, e.g. @hourly, @daily, @weekly

The latter can get quite complex, but there are online tools out there to help you with it. After defining when something should run, you can give a command or a script that is run at the appropriate time. The command or script has to be on the same line. The command to execute does not need to be a Slurm jobscript (i.e. should not contain #SBATCH lines).

These #SCRON lines and the following line comprise a single scrontab entry. All #SCRON lines following will be counted towards the next command.

You can list your currently defined scron jobs with scrontab -l.

Slurm cannot guarantee that the jobs will run at the requested times, but tries to schedule it es close as possible. Internally, jobs are submitted to Slurm and set with a specific BeginTime. Once a scron job ran, it will be requeued with a new BeginTime. These jobs will also show up in squeue.

Example

#SCRON -p fat
#SCRON -t 01:00:00
@daily /usr/users/mboden/update-database.sh
 
#SCRON -p medium
#SCRON -C scratch
#SCRON -t 05:00
#check scratch every 5 minutes
*/15 * * * * /usr/users/mboden/check-scratch.sh
1) scrontab uses the editor saved in the $EDITOR variable.
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