slurm: Call slurm_init() once before any call to Slurm API

[e4t]

Since Slurm 20.11, slurm_init() needs to be called before any call to the Slurm API to make sure the config file is read in. We cannot call it in mod_slurm_init() or in mod_slurm_wcoll() directly as it requires slurm to be configured before use, thus pdsh would fail whenever the slurm plugin is found but Slurm is not configured correctly.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.43 🎉

Comparison is base (3bc95a8) 64.20% compared to head (4adcddc) 64.64%.

❗ Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #148      +/-   ##
==========================================
+ Coverage   64.20%   64.64%   +0.43%     
==========================================
  Files          27       27              
  Lines        5588     5886     +298     
==========================================
+ Hits         3588     3805     +217     
- Misses       2000     2081      +81     

Impacted Files	Coverage Δ
src/pdsh/mod.c	76.44% <100.00%> (+0.94%)	⬆️
src/pdsh/opt.c	84.99% <100.00%> (-0.10%)	⬇️

... and 8 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[grondo]

Thanks!

We cannot call it in mod_slurm_init() or in mod_slurm_wcoll() directly as it requires slurm to be configured before use,

This looks fine to me, but could I ask why slurm_init() can't be called in mod_slurm_init() if any error is ignored (or saved for later examination if a Slurm option is utilized)? There may be a good reason, I was more curious than anything else.

[e4t]

Thanks!

We cannot call it in mod_slurm_init() or in mod_slurm_wcoll() directly as it requires slurm to be configured before use,

This looks fine to me, but could I ask why slurm_init() can't be called in mod_slurm_init() if any error is ignored (or saved for later examination if a Slurm option is utilized)? There may be a good reason, I was more curious than anything else.

@grondo Sorry for the late reply, I've missed your question.
I've tried to briefly describe this in the commit message: It was my initial approach as well, luckily Slurm was not configured on the build system so I caught it: slurm_init() requires Slurm to be configured, otherwise it will fail and exit() directly AFAIR - which it really shouldn't not do. This way, pdsh would fail every time the slurm module is found (ie during pdsh -h - even though it's not used as mod_slurm_init() is called every time the module is loaded even though it's not used. The only way around the Slurm quirkiness I saw was with this somewhat ugly 'hack'.
Meanwhile I've got bitten by my patch on older Slurm versions (< 20.11) as these don't expose slurm_init() through libslurm at all. I'll push an updated patch.

[grondo]

@e4t - sorry this one languished so long. Your solution works, and more people have been hitting this issue so I'm merging.