How to Create the Skeleton of an Operator - cniackz/public GitHub Wiki

Objective:

To create the skeleton of an operator

Diagram:

Recommendation:

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Steps:

• Prepare an empty folder to work with:

cd ~
rm -rf ~/tmp
cd ~
mkdir ~/tmp
cd ~/tmp

• Initialize the operator

operator-sdk init --domain example.com --repo github.com/my-org/my-operator

• Create the API:

operator-sdk create api --group apps --version v1alpha1 --kind MyApp

• In the controller, get the app instance & print the message from the custom resource:

• File:

subl /Users/cniackz/tmp/internal/controller/myapp_controller.go

func (r *MyAppReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {

    ...

    log := log.FromContext(ctx)

    // Fetch the MyApp instance
    var myapp appsv1alpha1.MyApp
    if err := r.Get(ctx, req.NamespacedName, &myapp); err != nil {
        return ctrl.Result{}, client.IgnoreNotFound(err)
    }

    // Print the message from the Custom Resource
    log.Info("Received MyResource", "message", myapp.Spec.Message)

    ...

• In the types file, add the message to the struct

subl /Users/cniackz/tmp/api/v1alpha1/myapp_types.go

type MyAppSpec struct {
	// INSERT ADDITIONAL SPEC FIELDS - desired state of cluster
	// Important: Run "make" to regenerate code after modifying this file

	// Foo is an example field of MyApp. Edit myapp_types.go to remove/update
	Foo string `json:"foo,omitempty"`

	Message string `json:"message,omitempty"`
}

• Then make and generate the files:

make generate
make manifests

• Build the image:

make docker-build IMG=radical-123

kind load docker-image docker.io/library/radical-123

createcluster

kubectl create namespace system
kubectl apply -k /Users/cniackz/tmp/config/crd
kubectl apply -k /Users/cniackz/tmp/config/rbac
kubectl apply -f /Users/cniackz/tmp/config/manager

• change deployment

subl /Users/cniackz/tmp/config/manager/manager.yaml

• Under containers add image and imagePullPolicy as below:

      containers:
      - command:
        - /manager
        args:
        - --leader-elect
        image: docker.io/library/radical-123
        imagePullPolicy: Never

k apply -f /Users/cniackz/tmp/config/manager/manager.yaml

• in manager-role cluster role do:

rules:
  - verbs:
      - create
    apiGroups:
      - ''
    resources:
      - events
  - verbs:
      - get
      - create
      - update
    apiGroups:
      - coordination.k8s.io
    resources:
      - leases

or apply below:

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: manager-role
rules:
- apiGroups:
  - ''
  resources:
  - events
  verbs:
  - create
- apiGroups:
  - coordination.k8s.io
  resources:
  - leases
  verbs:
  - get
  - create
  - update
- apiGroups:
  - apps.example.com
  resources:
  - myapps
  verbs:
  - create
  - delete
  - get
  - list
  - patch
  - update
  - watch
- apiGroups:
  - apps.example.com
  resources:
  - myapps/finalizers
  verbs:
  - update
- apiGroups:
  - apps.example.com
  resources:
  - myapps/status
  verbs:
  - get
  - patch
  - update

• apply CR

apiVersion: apps.example.com/v1alpha1
kind: MyApp
metadata:
  name: myapp-sample
spec:
  message: "Hello, Kubernetes Operator!"