Stop slurmd during slurmctld restart

[priteau]

Some Slurm configuration changes can cause compute nodes to go into invalid state if slurmctld is restarted while slurmd services are still running.

Stop slurmd services while slurmctld is being restarted. This has been tested not to affect running jobs.

Closes #199

[gemini-code-assist]

Summary of Changes

Hello @priteau, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a critical stability improvement for Slurm clusters by ensuring that slurmd services are temporarily stopped on compute nodes before slurmctld is restarted due to configuration updates. This proactive measure prevents potential invalid states on compute nodes that could arise from slurmctld restarting while slurmd is still active, thereby making Slurm configuration changes safer and more robust without impacting ongoing workloads.

Highlights

• Improved Slurm Stability: This change prevents compute nodes from entering an invalid state when slurmctld is restarted due to configuration changes while slurmd services are still running.
• Conditional slurmd Stoppage: A new Ansible task has been added to conditionally stop the slurmd service on relevant hosts before slurmctld is restarted, specifically when Slurm or GRES configuration files have changed.
• No Impact on Running Jobs: The implemented solution has been tested and confirmed not to affect running jobs during the slurmd stoppage and slurmctld restart process.

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[gemini-code-assist]

Code Review

This pull request correctly identifies a potential issue with restarting slurmctld while slurmd is running and implements a sound strategy to mitigate it by stopping slurmd services beforehand. The use of flush_handlers to orchestrate the service restarts is a good approach. My review focuses on a minor inconsistency in the conditions that trigger the slurmd stop, which could leave a gap in the protection this change provides. I've provided a specific suggestion to address this.