Signal Forwarding to Jobscripts

[cmeesters]

On clusters with the SLURM batch system, ordinary jobscripts are able to utilize sbatch's signal forwarding feature (see manual, syntax --signal=[{R|B}:]<sig_num>[@sig_time]) to send signals to the application before hitting the wall time. The use case is that applications may use the remaining time to stage back a checkpoint file onto the parallel file system.

To support this feature within this plugin:

• a flag has to be implemented and the --signal flag to be triggered upon a user request.
• the jobstep plugin must be able to receive that signal and forward it to the 3rd party application.

This feature request is related to issue #snakemake/snakemake#3241 .