The Single-use Daemonset Pattern and Pre-pulling Images in Kubernetes

The process of speeding up the creation of Kubernetes pods that require large Docker images can be enhanced by using a DaemonSet to pre-pull images, ensuring that the necessary Docker image is already on a node when a pod is scheduled to run. This approach is beneficial in scenarios where large images are involved and pods are frequently recreated, such as in scale-out scenarios. The method involves creating a Docker container that performs a pull command using a 'Docker in Docker' (dind) container, with the pod configured as a DaemonSet to run on every node. However, due to DaemonSet's limitation of always restarting pods, a workaround using an initContainer is employed to ensure the image is pulled only once, while a 'pause' container keeps the DaemonSet pod alive with minimal resource usage. This technique, although a workaround, is effective for pre-pulling Docker images to speed up Kubernetes pod deployment. The process is compatible with Codefresh, and a detailed implementation is available for reference.

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