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3-controller.md

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Implementing a controller

We will now create our ToastController to manage the Toast resources.

Steps

  1. Update the ToastReconciler.Reconcile() function to implement the Toaster update loop. Find and open the breakfast/internal/controller/toast_controller.go file.

First, we define a constant to represent how long to wait between updates:

const TOAST_INTERVAL = 10 * time.Second

Then we can fill in the Reconcile function as follows:

func (r *ToastReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
  logger := log.FromContext(ctx)

  // TODO(user): your logic here
  toast := &breakfastv1.Toast{}
  err := r.Get(ctx, req.NamespacedName, toast)

  if err != nil && client.IgnoreNotFound(err) == nil {
    logger.Info("Toast not found, assumed deleted")
    return ctrl.Result{}, nil
  }
  if client.IgnoreNotFound(err) != nil {
    logger.Error(err, "unable to fetch Toast")
    return ctrl.Result{}, err
  }

  if time.Now().Before(toast.Status.LastUpdated.Add(TOAST_INTERVAL)) {
    return ctrl.Result{}, nil
  }

  if toast.Status.Toastiness < toast.Spec.Toastiness {
    logger.Info("status toastiness < spec toastiness")
    toast.Status.Toastiness++
    toast.Status.Ready = false
    toast.Status.LastUpdated = metav1.Now()

    if err = r.Status().Update(ctx, toast); err != nil {
      logger.Error(err, "unable to update Toast")
      return ctrl.Result{}, err
    }

    return ctrl.Result{
      RequeueAfter: TOAST_INTERVAL,
    }, nil
  }

  // Update the status after the toastiness reaches the desired level
  toast.Status.Ready = true
  if err = r.Status().Update(ctx, toast); err != nil {
    logger.Error(err, "unable to update Toast")
    return ctrl.Result{}, err
  }
  // Don't requeue if the toast is ready
  return ctrl.Result{}, nil
}

This requires the packages time and metav1 to be added to the import list:

  import (
    "context"

+   "time"

+   metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/apimachinery/pkg/runtime"
    ctrl "sigs.k8s.io/controller-runtime"
    "sigs.k8s.io/controller-runtime/pkg/client"
    "sigs.k8s.io/controller-runtime/pkg/log"

    breakfastv1 "github.com/NewRedo/toaster-controller/breakfast/api/v1"
  )

  1. Build with make docker-build TAG=breakfast:latest

  2. If using a local kubernetes deployment, prevent kubernetes from pulling the image from a remote repository:

In breakfast/config/manager/manager.yaml:

          args:
            - --leader-elect
          image: controller:latest
+         imagePullPolicy: IfNotPresent
          name: manager
          securityContext:
  1. Deploy with make deploy TAG=breakfast:latest

Testing the controller

Add the sample toast resource, that was created in the previous section, to the cluster.

kubectl apply -f config/samples/breakfast_v1_toast.yaml

Repeated invocations of kubectl describe toast will show the toastiness increasing until it reaches the desired level.

Next Steps

Summary