Per https://slurm.schedmd.com/prolog_epilog.html, a wide range of information about the job is available in slurmd prolog/epilog scripts through environment variables. 

For example SLURM_JOB_CONSTRAINTS is useful for us as we sometimes need to do additional per-job setup when the node was rebooted with a particular dynamic node feature (thanks to the helper node_features plugin from https://bugs.schedmd.com/show_bug.cgi?id=9567). 

For node tweaks that don't require a reboot, we rely on --comment. For instance, to disable THP a user can do "--comment=transparent_hugepage=never" and the change is applied to the node in a Slurm epilog script. However we have to rely on "scontrol" to query the "Comment" field of the job today, which is not recommended per the documentation above:
> Prolog and Epilog scripts should be designed to be as short as possible and should not call Slurm commands (e.g. squeue, scontrol, sacctmgr, etc). Long running scripts can cause scheduling problems when jobs take a long time to start or finish. Slurm commands in these scripts can potentially lead to performance issues and should not be used.

There are multiple ways to workaround this, but adding SLURM_JOB_COMMENT (behaving similarly to SLURM_JOB_CONSTRAINTS) is probably straightforward to do and would eliminate the call to scontrol.