This is an attempt to support scaling from/to zero.
The basic idea is that we create a one-off "registration-only" runner pod on RunnerReplicaSet being scaled to zero, so that there is one "offline" runner, which enables GitHub Actions to queue jobs instead of discarding those.
GitHub Actions seems to immediately throw away the new job when there are no runners at all. Generally, having runners of any status, `busy`, `idle`, or `offline` would prevent GitHub actions from failing jobs. But retaining `busy` or `idle` runners means that we need to keep runner pods running, which conflicts with our desired to scale to/from zero, hence we retain `offline` runners.
In this change, I enhanced the runnerreplicaset controller to create a registration-only runner on very beginning of its reconciliation logic, only when a runnerreplicaset is scaled to zero. The runner controller creates the registration-only runner pod, waits for it to become "offline", and then removes the runner pod. The runner on GitHub stays `offline`, until the runner resource on K8s is deleted. As we remove the registration-only runner pod as soon as it registers, this doesn't block cluster-autoscaler.
Related to #447
* Fix acceptance helm test not using newly built controller image
* Locally build runner image instead of pulling it
* Revert runner controller image pull policy to always
and add a line to the test deployment to use IfNotPresent
* Change runner repository from summerwind/action-runner to the owner of actions-runner-controller.
Also fix some Makefile formatting.
* Undo renaming acceptance/pull to docker-pull
* Some env var cleanup
Rename USERNAME to DOCKER_USER(is still used for github too tho)
Add RUNNER_NAME var(defaults to $DOCKER_USER/actions-runner)
Add TEST_REPO(defaults to $DOCKER_USER/actions-runner-controller)
Images for `actions-runner:v${VERSION}` and `actions-runner:latest` tags are upgraded to Ubuntu 20.04.
If you would like not to upgrade Ubuntu in the runner image in the future, migrate to new tags suffixed with `-ubuntu-20.04` like`actions-runner:v${VERSION}-ubuntu-20.04`.
We also keep publishing the existing Ubuntu 18.04 images with new `actions-runner:v${VERSION}-ubuntu-18.04` tags. Please use it when it turned out that you had workflows dependent on Ubuntu 18.04.
Co-authored-by: Yusuke Kuoka <ykuoka@gmail.com>
