k8s-controller-duplicate-and-inject-configmap

A sample k8s controller that injects environment variables from a ConfigMap into a new Pod after admission based on an existing pod with the annotation(duplicate-and-duplicate-and-inject-configmap: $CONFIG_MAP_NAME).

Running the Project

This repo includes a Makefile; a few of the relevant targets are:

• create-kind-cluster: Creates a local Kind k8s cluster for local development.
• build-and-load-docker-image: Builds the controller's docker image and loads it into Kind.
• deploy: Applies a deployment for the controller, associated ServiceAccount and ClusterRole resources, and a sample ConfigMap to inject and a Pod with the annotation.
• clean: Deletes resources and local docker image.

Limitations

I built this as an initial foray into building with k8s instead of just against it. As a result, it really doesn't do anything complex.

The controller only does the following:

• Watches for new pods with the annotation
• Duplicates said pod, but with the contents of the specified ConfigMap.

It doesn't do any sort of validation in the ConfigMap, or checks for updated pods.