edge: Registration-only runner disappears before runners are up

[mikesplain]

Thanks for the great project! I've been testing out the new scaling to zero and I believe I've found a bug with #465. When runners are at zero and a registration runner is offline, a user pushes a commit or opens a PR, etc. to trigger a scale up with the webhook.

The runners begin starting up (YAY) but almost immediately the registration runner disappears (BOO). I think the issue is that it is removed before other runners are active (they're still starting)? I haven't been able to figure out the issue in the code, there may need to be more logic in https://github.com/actions-runner-controller/actions-runner-controller/pull/465/files#diff-5ec1753568c3eb77cc6c854abf50248883481cd011244012145cd5769e948ad6R119-R128 or so.

Anyway I'll let you know if I can debug further.

[mumoshu]

@mikesplain Hey! Thanks for testing the edge version of actions-runner-controller. That's super helpful.

That does seem to be caused by a potential bug in the controller.

My quick recall says that I might have forgotten to let it wait for runners to be up before deleting the registration-only runner, which matches exactly with your thought.

Let me confirm and fix it soon.