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We stand in solidarity with the Black community.

Racism is unacceptable.

It conflicts with the core values of the Kubernetes project and our community does not tolerate it.

You said something about main?

But first, remember how we said we’d come back to main.go again? Let’s take a look and see what’s changed, and what we need to add.

Apache License

Copyright 2020 The Kubernetes authors.

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

package main

import (

	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
	// to ensure that exec-entrypoint and run can make use of them.
	_ ""

	utilruntime ""
	clientgoscheme ""
	ctrl ""

	batchv1 ""

The first difference to notice is that kubebuilder has added the new API group’s package (batchv1) to our scheme. This means that we can use those objects in our controller.

If we would be using any other CRD we would have to add their scheme the same way. Builtin types such as Job have their scheme added by clientgoscheme.

var (
	scheme   = runtime.NewScheme()
	setupLog = ctrl.Log.WithName("setup")

func init() {


The other thing that’s changed is that kubebuilder has added a block calling our CronJob controller’s SetupWithManager method.

func main() {
old stuff
	var metricsAddr string
	var enableLeaderElection bool
	var probeAddr string
	flag.StringVar(&metricsAddr, "metrics-bind-address", ":8080", "The address the metric endpoint binds to.")
	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
		"Enable leader election for controller manager. "+
			"Enabling this will ensure there is only one active controller manager.")

	opts := zap.Options{
		Development: true,


	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
		Scheme:                 scheme,
		MetricsBindAddress:     metricsAddr,
		Port:                   9443,
		HealthProbeBindAddress: probeAddr,
		LeaderElection:         enableLeaderElection,
		LeaderElectionID:       "",
	if err != nil {
		setupLog.Error(err, "unable to start manager")
	if err = (&controllers.CronJobReconciler{
		Client: mgr.GetClient(),
		Log:    ctrl.Log.WithName("controllers").WithName("CronJob"),
		Scheme: mgr.GetScheme(),
	}).SetupWithManager(mgr); err != nil {
		setupLog.Error(err, "unable to create controller", "controller", "CronJob")
old stuff

We’ll also set up webhooks for our type, which we’ll talk about next. We just need to add them to the manager. Since we might want to run the webhooks separately, or not run them when testing our controller locally, we’ll put them behind an environment variable.

We’ll just make sure to set ENABLE_WEBHOOKS=false when we run locally.

	if os.Getenv("ENABLE_WEBHOOKS") != "false" {
		if err = (&batchv1.CronJob{}).SetupWebhookWithManager(mgr); err != nil {
			setupLog.Error(err, "unable to create webhook", "webhook", "CronJob")

	if err := mgr.AddHealthzCheck("healthz", healthz.Ping); err != nil {
		setupLog.Error(err, "unable to set up health check")
	if err := mgr.AddReadyzCheck("readyz", healthz.Ping); err != nil {
		setupLog.Error(err, "unable to set up ready check")

	setupLog.Info("starting manager")
	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
		setupLog.Error(err, "problem running manager")

Now we can implement our controller.