It turned out that #1179 broke static runners in a way it is no longer able to scale up at all when the desired replicas is updated.
This fixes that by correcting a certain short-circuit that is intended only for ephemeral runners to not mistakenly triggered for static runners.
I found that #1179 was unable to finish rollout of an RunnerDeployment update(like runner env update). It was able to create a new RunnerReplicaSet with the desired spec, but unable to tear down the older ones. This fixes that.
While testing #1179, I discovered that ARC sometimes stop resyncing RunnerReplicaSet when the desired replicas is greater than the actual number of runner pods.
This seems to happen when ARC missed receiving a workflow_job completion event but it has no way to decide if it is either (1) something went wrong on ARC or (2) a loadbalancer in the middle or GitHub or anything not ARC went wrong. It needs a standard to decide it, or if it's not impossible, how to deal with it.
In this change, I added a hard-coded 10 minutes timeout(can be made customizable later) to prevent runner pod recreation.
Now, a RunnerReplicaSet/RunnerSet to restart runner pod recreation 10 minutes after the last scale-up. If the workflow completion event arrived after the timeout, it will decrease the desired replicas number that results in the removal of a runner pod. The removed runner pod might be deleted without ever being used, but I think that's better than leaving the desired replicas and the actual number of replicas diverged forever.
Yusuke Kuoka