An Example Operator written in TypeScript based in This example from OpenShift.

Launch a kind cluster or have a kubeconfig ready for another cluster:

kind create cluster

Start by creating all the resources:

kustomize build resources | kubectl apply -f -

This will create the ts-operator namespace and populate it with ImageStreams, a BuildConfig and a Deployment running the operator.

It will also create MyCustomResource Custom Resource Definition and the mycustomresource-editor Role.

Tail the logs of the operator by running:

kubectl -n ts-operator logs -f deployment/ts-operator

In a different terminal, create an instance of the CRD by running:

kubectl create -f resources/memcached-sample.yaml

You will see a new Deployment called mycustomresource-sample with pods starting.

Now modify the size property in your Custom Resource:

kubectl edit mycustomresource mycustomresource-sample

Replace the size value from 1 to 2, then save. You will see the size of your deployment go from 1 to 2 and new pods starting.

You can delete all the resources created earlier by running:

kustomize build resources | kubectl delete -f -