kube-operator-demo

README

kube-operator-demo

Build a Kubernetes operator with Operator SDK

1. Create k3d demo-operator cluster (3 nodes) First, you need to install k3d distribution (allows to create containerized k3s clusters).

   k3d cluster create --api-port 127.0.0.1:6444 demo-operator --servers 3
   

2. Bootstrap a new Kubvernetes Operator

   • Project initialization

   operator-sdk init kube-operator-demo --domain=lfr31.com --repo github.com/lfranchini31/kube-operator-demo --license apache2 --owner "Lionel FRANCHINI"
   

   • Create a simple API:

   operator-sdk create api --group demo --version v1alpha1 --kind Demo --resource=true --controller=true
   

   • Modify the demo types in order to add:

     • a size attribute to DemoSpec
     • a pod array attribute to DemoStatus

     And launch 'make generate':

     make generate
     

   • Generating CRD manifests

     make manifests
     

     This makefile target will invoke controller-gen to generate the CRD manifests at config/crd/bases/demo.lfr31.com_demoes.yaml

3. Implement the Controller (Business Logic -> Core of this operator ;)!)

   • Create a demo Deployment if it doesn’t exist
   • Ensure that the Deployment foo and size are the same as specified by the Demo CR spec
   • Update the Demo CR status using the status writer with the names of the demo pods

   You can implement others features if you want ... to Infinity and Beyond!

4. Build and run the operator

    make install
   

   Once this is done, there are two ways to run the operator:

   • As Go program outside a cluster

   make run ENABLE_WEBHOOKS=false
   

   • As a Deployment inside a Kubernetes cluster
     • Build and push the image

     # Build the image
     export REGISTRY=<dockerhub-username>
     # you need to be loggued to Docker registry -> docker login
     make docker-build IMG=$REGISTRY/demo-operator:v0.0.1
     # Push the image to the docker hub registry
     make docker-push IMG=$REGISTRY/demo-operator:v0.0.1
     

     • Deploy the operator For this demo we will run the operator in the demo namespace which can be specified for all resources in config/default/kustomization.yaml

     cd config/default/ && kustomize edit set namespace "demo" && cd ../..
     

     Install cert manager before deploy your operator

     kubectl apply -f https://github.com/jetstack/cert-manager/releases/download/v1.1.0/cert-manager.yaml
     

     Run the following to deploy the operator (also install the RBAC manifests from config/rbac)

     make deploy IMG=$REGISTRY/demo-operator:v0.0.1
     

     $ kubectl get deploy
       NAME                                    READY   UP-TO-DATE   AVAILABLE   AGE
       demo-operator-controller-manager          1/1     1            1           20s
     

5. Create a Demo CR

   • Update the sample Demo CR manifest at config/samples/demo_v1alpha1_demo.yaml and define the spec as the following:

   apiVersion: demo.lfr31.com/v1alpha1
   kind: Demo
   metadata:
     name: demo-sample
   spec:
     foo: bar
     size: 3
   

   • Create the CR:

     kubectl apply -f config/samples/demo_v1alpha1_demo.yaml
     

     Ensure that the demo operator creates the deployment for the sample CR with the correct size:

     $ kubectl get deployment
      NAME                                    READY   UP-TO-DATE   AVAILABLE   AGE
      demo-operator-controller-manager   1/1     1            1           5m
      demo-sample                        3/3     3            3           1m
     

     Check the pods and CR status to confirm the status is updated with the demo pod names:

     $ kubectl get po
      NAME                                  READY     STATUS    RESTARTS   AGE
      demo-sample-9df5c78d7-5pmde           1/1       Running   0          1m
      demo-sample-9df5c78d7-5pmde           1/1       Running   0          1m
      demo-sample-9df5c78d7-5pmde           1/1       Running   0          1m
     

6. Clean-up

   • Delete the CR to uninstall Demo

   kubectl delete -f config/samples/demo_v1alpha1_demo.yaml
   

   • Uninstall the operator and its CRDs

   kustomize build config/default | kubectl delete -f -
   

(BONUS) - Create a monitoring namespace and deploy prometheus operator

• Add bitnami helm repository bash kubectl create ns monitoring - Install the helm chart bash helm upgrade --install -n monitoring prometheus prometheus-community/kube-prometheus-stack