Support to multiple dockers in single CI/RUNNER

[ndf-ti]

🚀 Feature Request: Support for Multiple Docker Runners in a Single CI Setup

📚 Context

We're exploring advanced configurations for GitHub Actions using Actions Runner Controller (ARC), particularly the new support for runner scale sets.

Start Point / Reference:
➡️ https://docs.github.com/en/actions/tutorials/use-actions-runner-controller/deploy-runner-scale-sets#runner-scale-set

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📌 Objective

Enable support for multiple Docker containers to run in isolation within a single ARC-based runner scale set. This is critical for use cases involving:

• Multi-service integration tests
• Containerized toolchains
• Parallel job execution in isolated containers

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💡 Proposed Solution

• Evaluate runner pod customization (runnerSpec.containers[]) to run sidecar Docker containers
• Validate the use of Docker-in-Docker (dind) or Kubernetes sidecars for job isolation
• Consider dynamic volume mounts and network namespaces per container

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🔍 To Investigate

• ARC compatibility with container job definitions inside workflow YAML
• Runner-level configuration to support multiple parallel containers per workflow
• Effects on auto-scaling behavior and resource limits in runner scale sets

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✅ Expected Outcome

A flexible runner architecture where multiple Docker jobs can run concurrently or sequentially within a single CI runner context — without requiring multiple full runners per container.

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