What Is a Docker Machine Executor?
A Docker machine executor is a runner configuration that provisions cloud virtual machines on demand, installs a Docker engine on each, and runs jobs as containers there. It was a common way to autoscale CI runners across cloud VMs. It has largely been superseded by container-orchestrator-based executors.
Why it matters
It pioneered on-demand CI capacity but carries operational overhead and is now deprecated in many setups. Understanding it explains why teams migrated to Kubernetes or managed runner platforms for autoscaling. The core idea, ephemeral VMs per job, still underlies modern approaches.
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