Runner Scale Set - CI/CD Glossary Definition
A runner scale set is an autoscaling pool of ephemeral runners managed by the Actions Runner Controller.
A runner scale set is a group of homogeneous ephemeral runners managed by the Actions Runner Controller that scales the number of runners up and down based on queued job demand.
Scale sets are the modern Kubernetes-native model for self-hosted autoscaling. The controller watches the job queue and creates or removes ephemeral runner pods to match demand.
How it scales
The controller polls GitHub for queued jobs assigned to the scale set and provisions one ephemeral runner per job, up to a configured maximum, then removes runners as jobs finish.
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