fix(runners): fix registration token API, shuffle rebalance, consolidate dirs

[sbryngelson]

Summary

• Add -X POST to gh_registration_token() — required by GitHub API, was causing 404 on runner creation
• Shuffle runner placement order during rebalance so sequential runner numbers spread across nodes (avoids overloading one node when jobs arrive in number order)
• Remove scratch dir from Phoenix RUNNER_PARENT_DIRS (all runners consolidated to project storage)

Test plan

• Verified create-runner works with the -X POST fix (created phoenix 1-4)
• Verified rebalance-runners dry run produces randomized order
• Verified all 10 runners healthy after rebalance (check-runners)

🤖 Generated with Claude Code

[github-actions]

Claude Code Review

Head SHA: c417fc8

Files changed:

• 3
• misc/runners/common/rebalance-runners.sh
• misc/runners/common/runner-lib.sh
• misc/runners/phoenix/config.sh

Findings:

• misc/runners/phoenix/config.sh: runner_install_dir now uses an out-of-bounds array index.
  The diff removes the first entry (/storage/scratch1/…/mfc-runners) from RUNNER_PARENT_DIRS, shifting the remaining entry from index 1 to index 0. However, runner_install_dir() in the same file still hardcodes RUNNER_PARENT_DIRS[1]:

  local parent="${RUNNER_PARENT_DIRS[1]}"

  After this change RUNNER_PARENT_DIRS[1] is empty/unset, so parent will be an empty string. Any call to runner_install_dir will attempt to resolve paths like //actions-runner-N, causing installs to silently target the filesystem root or fail. The index should be updated to RUNNER_PARENT_DIRS[0].

[github-actions]

Claude Code Review

Head SHA: c417fc8

Files changed:

• 3
• misc/runners/common/rebalance-runners.sh
• misc/runners/common/runner-lib.sh
• misc/runners/phoenix/config.sh

Findings:

• rebalance-runners.sh: Shuffle is O(n²) due to full array rebuild each iteration — The Fisher-Yates-style loop rebuilds to_place every iteration via to_place=("${to_place[@]:0:$rand}" "${to_place[@]:$((rand+1))}"), which copies all remaining elements. For typical runner counts (tens of runners) this is benign, but if many runners are simultaneously offline the cost grows quadratically. A simpler approach is to swap the chosen element with the last and shrink the array by one, keeping the loop O(n).

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: f0c6930a-221b-434b-b250-b94d3ae9c73c

📥 Commits

Reviewing files that changed from the base of the PR and between 6120810 and c417fc8.

📒 Files selected for processing (3)

• misc/runners/common/rebalance-runners.sh
• misc/runners/common/runner-lib.sh
• misc/runners/phoenix/config.sh

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📝 Walkthrough

Walkthrough

Three shell script files were modified. A randomization algorithm was added to rebalance-runners.sh to shuffle the ordering of entries before move assignment. The runner-lib.sh file was updated to explicitly specify the POST HTTP method when requesting a registration token. In phoenix/config.sh, one shared storage directory path was removed from the RUNNER_PARENT_DIRS array, which affects runner installation directory selection and runner discovery.

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