Custom Resources and Operators

kubebuilder init --domain example.com --repo github.com/example/bookshelf-operator
kubebuilder create api --group bookshelf --version v1 --kind BookshelfBackup --resource --controller
make manifests      # regenerate the CRD from Go type markers
make install        # apply the CRDs to the current cluster
make run            # run the controller locally against that cluster

func (r *BookshelfBackupReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	var backup bookshelfv1.BookshelfBackup
	if err := r.Get(ctx, req.NamespacedName, &backup); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err) // deleted: nothing to do
	}

	// Deletion: clean up external state, then release the finalizer.
	if !backup.DeletionTimestamp.IsZero() {
		if controllerutil.ContainsFinalizer(&backup, finalizerName) {
			if err := r.deleteRemoteBackups(ctx, &backup); err != nil {
				return ctrl.Result{}, err
			}
			controllerutil.RemoveFinalizer(&backup, finalizerName)
			return ctrl.Result{}, r.Update(ctx, &backup)
		}
		return ctrl.Result{}, nil
	}

	// Register the finalizer so the deletion branch above can run later.
	if controllerutil.AddFinalizer(&backup, finalizerName) {
		if err := r.Update(ctx, &backup); err != nil {
			return ctrl.Result{}, err
		}
	}

	// Ensure the CronJob that performs the backup exists and is owned by this resource.
	// CreateOrUpdate first reads the live object into cron, so the desired state is set in the mutate function.
	cron := &batchv1.CronJob{ObjectMeta: metav1.ObjectMeta{Name: backup.Name + "-backup", Namespace: backup.Namespace}}
	if _, err := controllerutil.CreateOrUpdate(ctx, r.Client, cron, func() error {
		cron.Spec = desiredCronJobSpec(&backup)
		return ctrl.SetControllerReference(&backup, cron, r.Scheme)
	}); err != nil {
		return ctrl.Result{}, err
	}

	backup.Status.Phase = "Scheduled"
	return ctrl.Result{}, r.Status().Update(ctx, &backup)
}