This is a sample operator for demonstrating some of the basic concepts of a Kubernetes Operator.
It manages a go present deployment by creating the necessary configmap, deployment and service. The main CRD contains the contents of the slides that will be hosted by present, but the deployment itself picks it up from a configmap. On an update of the content, the operator restarts (deletes) the pods in the deployment, so they will pick up the new contents from the configmap.
This is a sample Kubebuilder project, so generating code, creating CRD YAMLs and deploying code is done in the standard way.
Complex operators are too difficult to understand when someone just met the concept, but it's good to see things working instead of only reading about it. Kubebuilder examples (CronJob, ReplicaSet) are great, but they are mostly controllers instead of an operator. This is the smallest operator example that I could think of and that holds on its own but still has some basic ideas of why an operator could be helpful.
Just run make.
Point your Kubernetes context to the right cluster, and run make install
IMG=<image-name>:<tag> make docker-build
IMG=<image-name>:<tag> make docker-push
Once you have a docker image built and pushed to a repo that's available from the cluster, just run:
IMG=<image-name>:<tag> make deploy
There is an example CR in the samples directory, just apply it directly.
kubectl apply -f config/samples/example_v1alpha1_presentation.yaml
The service is of type ClusterIP, the easiest way to access is to port-forward the service, but you can also use an ingress, or change the type in the code to LoadBalancer, maybe create a CRD property out of it.
kubectl port-forward service/present 3999:80
Add a second CRD for contents only. Every CR could represent a new slide, so the main CR would only hold parameters of the deployment.
Also I'm pretty sure that there are some bugs in the code, and there's always room for improvement so all contributions are welcome.