Runner Autoscaler - CI/CD Glossary Definition
A runner autoscaler watches the job queue and scales the runner fleet up and down automatically, so you pay for capacity roughly in proportion to demand.
A runner autoscaler is a controller that adds or removes CI runners based on demand, for example creating runners when jobs are queued and destroying idle ones to save cost.
Autoscalers such as actions-runner-controller (ARC) or managed platforms remove the need to keep a fixed pool of always-on runners.
Scaling signals
Most autoscalers scale on queued-job count or webhook events, then apply a cooldown before scaling in to avoid thrashing when jobs arrive in bursts.
In CI
Good autoscaling balances two costs: idle runners waste money, but scaling from zero adds cold-start latency to the first job in a burst. Warm pools trade a little cost for lower latency.