/Website-Kubernetes-Operator

Primary LanguageC#

Website operator

This repository contains an example schema of an operator written in .Net. You could use it in order to start develop your first Kubernetes operator!

The schema contains three elements:

  • Controller (a.k.a. Reconciler)
  • Entity
  • Finalizer

The controller is going to manage the "reconcile" step. It will watch over the observed resources and takes care of being sure that the k8s cluster state and the desired state are the same.

The entity described the state that should be observed by the controller.

The finalizer has the responsibility of dispose unused resources.

💪🏻 Working software exercises

You should start from this schema and implement the following feature:

  • feat n.1: Create a Pod with image nginx everytime a new custom resource of type website has been created
  • feat n.2: When a custom resource has been deleted, remove the linked resources (Pod)
  • feat n.3: When a new custom resource has been created or updated, the operator should deploy a deployment manifest and take the number of replicas from the new custom resource
  • feat n.4: Show time: 🎉 Create a service for that deployment and retrieve the public ip address.
  • feat n.5: When the pod starts, update the default nginx index.html and put inside a short description from the custom resource

How to generate manifests

You could use the KubeOps.Cli tool. It allows you to generate the needed files for your operator as well as managing resources in your Kubernetes cluster.

dotnet new tool-manifest
dotnet tool install KubeOps.Cli
dotnet kubeops gen op website --out ./manifests
//update the image in kustomization.yaml with the operator docker image you'll use

How to run in local env

If you want to test the operator locally you could easily run it in a local minikube instance.

Build operator image:

docker buildx build . -f manifests/Dockerfile -t operator

set the imagePullPolicy: IfNotPresent property in the generated deployment

  containers:
  - env:
    - name: POD_NAMESPACE
      valueFrom:
        fieldRef:
          fieldPath: metadata.namespace
    image: operator
    name: operator
    imagePullPolicy: IfNotPresent

Load the image in your local minikube cluster

minikube image load operator:latest

Apply it:

kubectl apply -k manifests

Custom resource example

    apiVersion: intre.it/v1
    kind: website
    metadata:
      name: my-website
    namespace: default
    spec:
    name: "My Website"

Notes & FAQ

Minikube images aren't updated

If you are using minikube and you are not able to see the updated image, you could try to run the following command:

minikube image rm operator:latest

And upload the new image again with

minikube image load operator:latest

Common words

(*) Reconciles: it stands for the act of the operator to edit (reconcile) the status of the kubernetes cluster as we want (looking at the custom resource)