Actions Runner Controller
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I have used Actions Runner Controller (ARC) to run self-hosted GitHub Actions jobs on Kubernetes. ARC manages runner pods and scales them in response to assigned jobs. The current GitHub-supported approach uses autoscaling runner scale sets; older autoscaling modes remain in the project as legacy options.
How runner scale sets work
The ARC controller runs in the cluster and manages a runner scale set. A listener receives available jobs from GitHub, adjusts the desired number of ephemeral runners, and creates runner pods. A workflow routes a job to the scale set by using its name in runs-on.
jobs:
build:
runs-on: arc-runner-set
steps:
- uses: actions/checkout@v4
- run: echo "Running on an ARC runner"Here, arc-runner-set is the Helm release name of the runner scale set, unless runnerScaleSetName overrides it.
Deployment choices
ARC uses separate Helm charts for the controller and each runner scale set. A scale set points at a repository, organization, or enterprise through githubConfigUrl. For repository and organization runners, GitHub recommends a GitHub App for API authentication. Keep the App credentials in a Kubernetes Secret and reference that Secret from the scale-set values instead of putting credentials on the Helm command line.
Set minRunners for idle capacity and maxRunners to cap concurrency. Leaving both unset allows the scale set to return to zero when there are no active jobs. Use runner groups to restrict which repositories can use a scale set.
Operational boundaries
- Put runner pods in a different namespace from the ARC controller.
- Treat workflow code as untrusted when deciding cluster access, network reachability, and credential exposure.
- Keep production workloads isolated from runner workloads where the risk requires it.
- Retain controller, listener, and ephemeral runner logs; the runner pods disappear after jobs complete.
- Watch job queue time, pod scheduling failures, runner startup time, and failed registration when diagnosing capacity or authentication problems.
See GitHub’s ARC overview , getting-started guide , and runner scale-set deployment guide for current setup details. The broader workflow and trust model is covered in GitHub Actions.