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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.

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Copyright 2024 The Kubernetes authors.

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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 ""
	metricsserver ""

	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
	var secureMetrics bool
	var enableHTTP2 bool
	flag.StringVar(&metricsAddr, "metrics-bind-address", "0", "The address the metric endpoint binds to. "+
		"Use the port :8080. If not set, it will be '0 in order to disable the metrics server")
	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.")
	flag.BoolVar(&secureMetrics, "metrics-secure", false,
		"If set the metrics endpoint is served securely")
	flag.BoolVar(&enableHTTP2, "enable-http2", false,
		"If set, HTTP/2 will be enabled for the metrics and webhook servers")
	opts := zap.Options{
		Development: true,


	// if the enable-http2 flag is false (the default), http/2 should be disabled
	// due to its vulnerabilities. More specifically, disabling http/2 will
	// prevent from being vulnerable to the HTTP/2 Stream Cancellation and
	// Rapid Reset CVEs. For more information see:
	// -
	// -
	disableHTTP2 := func(c *tls.Config) {
		setupLog.Info("disabling http/2")
		c.NextProtos = []string{"http/1.1"}

	tlsOpts := []func(*tls.Config){}
	if !enableHTTP2 {
		tlsOpts = append(tlsOpts, disableHTTP2)

	webhookServer := webhook.NewServer(webhook.Options{
		TLSOpts: tlsOpts,

	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
		Scheme: scheme,
		Metrics: metricsserver.Options{
			BindAddress:   metricsAddr,
			SecureServing: secureMetrics,
			TLSOpts:       tlsOpts,
		WebhookServer:          webhookServer,
		HealthProbeBindAddress: probeAddr,
		LeaderElection:         enableLeaderElection,
		LeaderElectionID:       "",
		// LeaderElectionReleaseOnCancel defines if the leader should step down voluntarily
		// when the Manager ends. This requires the binary to immediately end when the
		// Manager is stopped, otherwise, this setting is unsafe. Setting this significantly
		// speeds up voluntary leader transitions as the new leader don't have to wait
		// LeaseDuration time first.
		// In the default scaffold provided, the program ends immediately after
		// the manager stops, so would be fine to enable this option. However,
		// if you are doing or is intended to do any operation such as perform cleanups
		// after the manager stops then its usage might be unsafe.
		// LeaderElectionReleaseOnCancel: true,
	if err != nil {
		setupLog.Error(err, "unable to start manager")
	if err = (&controller.CronJobReconciler{
		Client: mgr.GetClient(),
		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.