Step 1: Install Kubebuilder

Kubebuilder is a tool that simplifies building Kubernetes APIs and controllers. You can install Kubebuilder on your local machine by following the installation instructions in the official documentation.

Step 2: Initialize a new Kubebuilder project

After installing Kubebuilder, you can initialize a new Kubebuilder project by running:

kubebuilder init --domain example.com --repo github.com/example/my-operator This command initializes a new Git repository on your local machine and scaffolds out the basic directory structure of your operator.

Step 3: Create a new API definition

In Kubebuilder, an API definition defines the Kubernetes resources that your operator will manage. To create a new API definition:

kubebuilder create api --group mygroup --version v1 --kind MySecret This command creates a new Kubernetes Custom Resource Definition (CRD) called "MySecret" in your operator. The CRD specifies the schema for your secrets and how instances of the "MySecret" object are created, updated, and deleted.

Step 4: Generate the controller code

Kubebuilder uses code generation to generate the boilerplate code for your controllers. To generate the controller code for your MySecret definition, run:

kubebuilder create webhook --group mygroup --version v1 --kind MySecret --defaulting --programmatic-validation This command scaffolds out the basic controller implementation and registration code. The controller implementation handles the reconciliation loop for your operator.

Step 5: Implement the reconciliation loop

In your controller implementation, you need to implement the reconciliation loop for your operator. The reconciliation loop checks the state of your "MySecret" objects and updates the corresponding Kubernetes secrets as needed. Here is some sample code that demonstrates how to fetch data from an API with bearer authentication and use it to create or update a Kubernetes secret:

func (r *MySecretReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) { ctx := context.Background() log := r.Log.WithValues("mysecret", req.NamespacedName)

// Fetch the MySecret object.
mySecret := &mygroupv1.MySecret{}
if err := r.Get(ctx, req.NamespacedName, mySecret); err != nil {
    if errors.IsNotFound(err) {
        // Ignore deleted MySecret objects.
        return ctrl.Result{}, nil
    }
    // Return error if we can't fetch the MySecret object.
    return ctrl.Result{}, err
}

// Fetch data from the API with bearer authentication.
bearerToken := "my-bearer-token"
apiUrl := "https://my-api-url.com"
httpClient := &http.Client{
    Timeout: time.Second * 10,
}
req, err := http.NewRequestWithContext(ctx, "GET", apiUrl, nil)
if err != nil {
    return ctrl.Result{}, err
}
req.Header.Add("Authorization", fmt.Sprintf("Bearer %s", bearerToken))
resp, err := httpClient.Do(req)
if err != nil {
    return ctrl.Result{}, err
}
defer resp.Body.Close()

// Parse the API response body as a map of key-value pairs.
kvPairs := map[string]string{}
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
    return ctrl.Result{}, err
}
if err := json.Unmarshal(body, &kvPairs); err != nil {
    return ctrl.Result{}, err
}

// Find or create a Kubernetes secret with the same name as the MySecret object.
secret := &corev1.Secret{}
err = r.Get(ctx, req.NamespacedName, secret)
if err != nil && errors.IsNotFound(err) {
    // Create a new Kubernetes secret if it doesn't exist.
    secret = &corev1.Secret{
        ObjectMeta: metav1.ObjectMeta{
            Name:      mySecret.Name,
            Namespace: mySecret.Namespace,
        },
        StringData: map[string]string{},
    }
}

// Add or update the key-value pairs in the Kubernetes secret.
for k, v := range kvPairs {
    secret.StringData[k] = v
}
err = r.Update(ctx, secret)
if err != nil {
    return ctrl.Result{}, err
}

// Requeue the reconciliation after a 5 minute delay.
return ctrl.Result{
    RequeueAfter: time.Minute * 5,
}, nil

} Note that this example assumes that your API returns a JSON-encoded map of key-value pairs. You may need to adjust the code to parse the data returned by your API.

Step 6: Build and deploy the operator

You can build and deploy your operator to a Kubernetes cluster by running the following commands:

make docker-build docker-push IMG=/: make deploy IMG=/: The first command builds and pushes the operator Docker image to a container registry. The second command deploys the operator to your Kubernetes cluster.

Step 7: Test the operator

To test your operator, create a new instance of the "MySecret" object in your Kubernetes cluster. The operator should automatically fetch data from your API and update the corresponding Kubernetes secret.

I hope this helps you create a basic Kubernetes operator that fetches data from an API and updates Kubernetes secrets as needed. Let me know if you have any questions or need further assistance!