fix(autoscale): recycle GitHub runners reported offline - #98
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Purpose: - Recover locally healthy GitHub runner containers whose control-plane sessions have gone offline. Before: - Autoscale trusted local listener processes and Docker health only. - A silent GitHub session failure stayed idle and suppressed capacity growth. Problem: - All build hosts can retain healthy containers while GitHub has no available runners. Resolution: - Cache the GitHub runner inventory for 60 seconds on the host. - Recycle an idle runner after two consecutive offline readings. - Preserve busy runners and retain capacity when the API is unavailable. Verification: - Added focused liveness and reaper regression coverage. - Passed the Linux repository check suite.
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📝 WalkthroughWalkthroughGitHub runner liveness detection now caches API status, requires repeated offline confirmations, and integrates with runner reaping. New tests cover cache reuse, busy runners, confirmed removal, and API failures. ChangesGitHub runner liveness
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🟡 Moderate · up to This change can automatically recycle locally healthy runners when GitHub reports them offline, but the current implementation may treat one cached observation as two confirmations, carry stale confirmation state into a replacement runner, or misassociate runner status. That could remove healthy build capacity, so the PR needs explicit owner acceptance or fixes before merging. Sequence Diagram(s)sequenceDiagram
participant RunnerFarm
participant GitHubProvider
participant GitHubAPI
participant RunnerRemoval
RunnerFarm->>GitHubProvider: refresh runner liveness
GitHubProvider->>GitHubAPI: request runner statuses
GitHubAPI-->>GitHubProvider: return runner inventory
GitHubProvider-->>RunnerFarm: provide cached status
RunnerFarm->>GitHubProvider: confirm offline runner
GitHubProvider-->>RunnerFarm: return confirmation result
RunnerFarm->>RunnerRemoval: remove confirmed offline runner
Suggested reviewers: Poem
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In `@src/usr/local/emhttp/plugins/ci-runner-farm/include/providers/github.sh`:
- Around line 124-126: Update github_offline_runner_confirmed in
src/usr/local/emhttp/plugins/ci-runner-farm/include/providers/github.sh at lines
124-126 to associate the confirmation marker with the cache timestamp or
inventory generation, incrementing only after a newer successful refresh reports
the runner offline. Update tests/github-liveness.sh at lines 41-45 to keep
repeated checks against one cache generation unconfirmed, then refresh with a
new offline response before asserting confirmation.
In `@tests/github-liveness.sh`:
- Line 39: Update the cache-reuse assertion in github-liveness.sh to invoke
github_runner_liveness_refresh again before checking the API log count, so the
test exercises the refresh function’s cached-return path while preserving the
existing expectation that no additional API request occurs.
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src/usr/local/emhttp/plugins/ci-runner-farm/include/providers/github.shsrc/usr/local/emhttp/plugins/ci-runner-farm/include/runner-farm.shtests/check.shtests/github-liveness.sh
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- Purpose: reduce the frequency of GitHub runner inventory requests.\n- Before: successful liveness responses were cached for 60 seconds.\n- Problem: the polling cadence was more aggressive than needed for stale-session recovery.\n- Resolution: cache successful liveness responses for 300 seconds while keeping two offline confirmations.\n- Verification: cover the five-minute cache boundary and pass the Linux repository checks.
- Purpose: make offline confirmation match the five-minute polling interval.\n- Before: two autoscale passes could count one cached GitHub response twice.\n- Problem: a 30-second autoscale loop could recycle a runner after about one minute.\n- Resolution: record the cache timestamp with each confirmation and increment only after a new inventory refresh.\n- Verification: cover cached reuse, cache expiry, distinct confirmations, and pass the Linux repository checks.
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Summary
Recover GitHub Actions runners whose local containers remain healthy after their GitHub control-plane sessions go offline.
Why This Exists
The build fleet recently showed every selected runner as offline while Docker containers and listener processes remained healthy. The current autoscaler trusts local process state, so it treated those runners as idle capacity and did not replace them.
A manual fleet restart restored service and the runners immediately accepted queued jobs.
Resolution
The autoscale reaper now reads the GitHub runner inventory through a host-side cache. It recycles an idle managed runner after two consecutive offline readings from distinct inventory refreshes.
Successful liveness responses remain cached for five minutes. This reduces API traffic while keeping recovery within roughly five to ten minutes after two offline confirmations.
The reaper keeps busy runners and does not recycle runners when the GitHub API response is unavailable or incomplete.
Reviewer Considerations
Behavior Changes
A locally running, Docker-healthy GitHub runner that GitHub reports offline is replaced automatically when it remains idle across two fresh liveness checks.
Implementation Summary
Verification
Risk
Low. The change is limited to autoscale recovery. API failures preserve existing runners instead of causing destructive action.