@Tina,
Figure slurmd reads the config in ones and runs with it. You would need to have it recheck regularly to see if there are any changes. This is exactly what 'scontrol reconfig' does: tells all the slurm nodes to recheck the config.
@Steven,
It seems to me you could just have a monitor daemon that keeps
things up-to-date.
It could watch for the alert that AWS sends (2 minute warning,
IIRC) and take appropriate action of drain the node and
cancel/checkpoint a job.
In addition, it could keep an eye on things in the event a warning
wasn't received and a node 'vanishes'. I suspect Nagios even has
the hooks to make that work. You could also email the user to let
them know their job was ended due to spot being pulled.
Just some ideas,
Brian Andrus