fix(nomad): handle "No running jobs" text output from nomad job status

[veeso]

Nomad ignores the -json flag when there are no jobs and returns plain
text instead of an empty JSON array, which caused jq parse failures in
count_eligible_nodes.sh. Treat this case as zero busy nodes.

Summary

TODO:

• All code changes are reflected in docs, including module-level docs
• All new/edited/removed scenarios are reflected in summary visualiser tool (see checklist)
• I ran the Nomad CI workflow successfully on my branch

Note that all commits in a PR must follow Conventional Commits before it can be merged, as these are used to generate the changelog

Summary by CodeRabbit

• Bug Fixes

  • Improved error messaging and warnings for command failures and invalid outputs.
  • Correct handling of cases with no running jobs and more accurate running-allocation counts.

• Chores

  • Made data collection and validation more robust to prevent silent failures during processing.

[claude]

Claude finished @veeso's task in 20s —— View job

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No issues found.

[github-actions]

The following will be added to the changelog

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[0.6.1] - 2026-03-18

Bug Fixes

• (nomad) Handle "No running jobs" text output from nomad job status
  • Nomad ignores the -json flag when there are no jobs and returns plain text instead of an empty JSON array, which caused jq parse failures in count_eligible_nodes.sh. Treat this case as zero busy nodes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 7d0a1484-6969-4d50-96b0-ad98dc1bdcd1

📥 Commits

Reviewing files that changed from the base of the PR and between 2e0f0d9 and d6aaf2a.

📒 Files selected for processing (1)

• nomad/scripts/count_eligible_nodes.sh

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Walkthrough

Replaced a streamed jq pipeline in nomad/scripts/count_eligible_nodes.sh with buffered capture of Nomad stdout/stderr, added explicit error and stderr reporting, handled "No running jobs" text, validated JSON before parsing, and computed running allocations from the validated JSON.

Changes

Cohort / File(s)	Summary
Shell script robustness & error handling nomad/scripts/count_eligible_nodes.sh	Capture Nomad stdout/stderr into variables, print detailed errors on command failure, warn on stderr output, handle "No running jobs" case, validate JSON before jq processing, and compute busy_json from the validated jobs_json.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• cdunster
• ThetaSinner
• ddd-mtl

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: handling the 'No running jobs' text output from nomad job status command, which matches the core fix in the changeset.
Description check	✅ Passed	The PR description explains the issue (Nomad ignoring -json flag and returning plain text), its impact (jq parse failures), and the solution (treating it as zero busy nodes). It includes the required template sections and TODO checklist items.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/fix-count-eligible-nodes-no-running-jobs

📝 Coding Plan

• Generate coding plan for human review comments

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

nomad/scripts/count_eligible_nodes.sh (1)

72-74: Please mirror this fallback in the module docs too.

The inline note is helpful, but this Nomad quirk now affects the script’s contract and should also be called out in the file header/module docs.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@nomad/scripts/count_eligible_nodes.sh` around lines 72 - 74, Add a short
module-docs/header note explaining the Nomad quirk: when there are no running
jobs the API returns the literal string "No running jobs" rather than JSON, and
this script maps that to an empty JSON array by setting busy_json='[]' (see the
conditional that checks jobs_json and assigns busy_json). Update the top-of-file
comment block (module docs) to describe this contract, include the exact string
"No running jobs" and the resulting behavior (busy_json becomes '[]'), and
mirror that note in any accompanying README or module documentation to make the
fallback explicit to callers and maintainers.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@nomad/scripts/count_eligible_nodes.sh`:
- Around line 67-79: The script currently mixes stdout and stderr into jobs_json
(via 2>&1) which breaks the "No running jobs" check and jq validation; change to
capture stdout and stderr separately (e.g., capture stdout into jobs_stdout and
stderr into jobs_stderr), perform the "No running jobs" string comparison and jq
-e validation only against jobs_stdout, and only log jobs_stderr when non-empty;
also avoid buffering the entire payload into a single variable by streaming
jobs_stdout directly into jq to produce busy_json (reference the
jobs_json/busy_json variables and the nomad job status invocation via $NOMAD).

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Nitpick comments:
In `@nomad/scripts/count_eligible_nodes.sh`:
- Around line 72-74: Add a short module-docs/header note explaining the Nomad
quirk: when there are no running jobs the API returns the literal string "No
running jobs" rather than JSON, and this script maps that to an empty JSON array
by setting busy_json='[]' (see the conditional that checks jobs_json and assigns
busy_json). Update the top-of-file comment block (module docs) to describe this
contract, include the exact string "No running jobs" and the resulting behavior
(busy_json becomes '[]'), and mirror that note in any accompanying README or
module documentation to make the fallback explicit to callers and maintainers.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: da8cd680-b948-4ffd-b70f-b50cc61f8819

📥 Commits

Reviewing files that changed from the base of the PR and between b9fb479 and 2e0f0d9.

📒 Files selected for processing (1)

• nomad/scripts/count_eligible_nodes.sh

[ThetaSinner]

Looks good, coderabbit suggestion may be worth a look

[cocogitto-bot]

✔️ d6aaf2a - Conventional commits check succeeded.