fix: Re-use existing runner scale set instead of panicking on startup

[baburciu]

When a pod crashes or restarts without clean shutdown, the runner scale set remains registered in GitHub. According to actions/actions-runner-controller#3035, there's no GH API to purge stale runner scale sets.

When the application restarts after an unclean shutdown (crash, OOMKill, pod eviction, CrashLoopBackOff), the runner scale set remains registered but offline in GitHub:

On the next startup, CreateRunnerScaleSet fails with:

panic: unable to create runner <name>, err: 400 - had issue communicating with
Actions backend: The runner scale set already exists in runner group Default.

This puts the pod into a permanent CrashLoopBackOff, because every restart attempt hits the same stale scale set and panics again.

Root cause: main.go unconditionally calls CreateRunnerScaleSet without first checking whether one already exists. The cleanup goroutine that deletes the scale set on shutdown only runs on graceful SIGTERM — it does not run when the process panics or is force-killed.

Fix: Before attempting to create a new runner scale set, call GetRunnerScaleSet (which already exists in the codebase) to check for an existing one. If found, re-use it. If not, create a new one as before.

  // Before (always creates, panics if exists)
  runnerScaleSet, err := actionsClient.CreateRunnerScaleSet(ctx, &types.RunnerScaleSet{...})

  // After (get-or-create)
  runnerScaleSet, err := actionsClient.GetRunnerScaleSet(ctx, groupId, runnerName)
  if runnerScaleSet != nil {
      logger.Infof("found existing runner scale set %s (id: %d), re-using it", ...)
  } else {
      runnerScaleSet, err = actionsClient.CreateRunnerScaleSet(ctx, &types.RunnerScaleSet{...})
  }

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com

[ispasov]

@baburciu Thank you for your contribution.
I see that this is still in draft.
Meanwhile it is something that we have already implemented. You can check it out here #65

[baburciu]

@ispasov thank you, I forgot to make it ready upon testing. I'll close mine