Setting up the webhooks

Our conversion is in place, so all that’s left is to tell controller-runtime about our conversion.

Normally, we’d run

kubebuilder create webhook --group batch --version v1 --kind CronJob --conversion

to scaffold out the webhook setup. However, we’ve already got webhook setup, from when we built our defaulting and validating webhooks!

Webhook setup...

project/api/v1/cronjob_webhook.go
Apache License

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

http://www.apache.org/licenses/LICENSE-2.0

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.

Go imports
package v1

import (
	"github.com/robfig/cron"

	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	validationutils "k8s.io/apimachinery/pkg/util/validation"
	"k8s.io/apimachinery/pkg/util/validation/field"

	ctrl "sigs.k8s.io/controller-runtime"
	logf "sigs.k8s.io/controller-runtime/pkg/runtime/log"
	"sigs.k8s.io/controller-runtime/pkg/webhook"
)
var cronjoblog = logf.Log.WithName("cronjob-resource")

This setup is doubles as setup for our conversion webhooks: as long as our types implement the Hub and Convertible interfaces, a conversion webhook will be registered.

func (r *CronJob) SetupWebhookWithManager(mgr ctrl.Manager) error {
	return ctrl.NewWebhookManagedBy(mgr).
		For(r).
		Complete()
}
Existing Defaulting and Validation
var _ webhook.Defaulter = &CronJob{}

// Default implements webhook.Defaulter so a webhook will be registered for the type
func (r *CronJob) Default() {
	cronjoblog.Info("default", "name", r.Name)

	if r.Spec.ConcurrencyPolicy == "" {
		r.Spec.ConcurrencyPolicy = AllowConcurrent
	}
	if r.Spec.Suspend == nil {
		r.Spec.Suspend = new(bool)
	}
	if r.Spec.SuccessfulJobsHistoryLimit == nil {
		r.Spec.SuccessfulJobsHistoryLimit = new(int32)
		*r.Spec.SuccessfulJobsHistoryLimit = 3
	}
	if r.Spec.FailedJobsHistoryLimit == nil {
		r.Spec.FailedJobsHistoryLimit = new(int32)
		*r.Spec.FailedJobsHistoryLimit = 1
	}
}

// TODO(user): change verbs to "verbs=create;update;delete" if you want to enable deletion validation.
// +kubebuilder:webhook:verbs=create;update,path=/validate-batch-tutorial-kubebuilder-io-v1-cronjob,mutating=false,failurePolicy=fail,groups=batch.tutorial.kubebuilder.io,resources=cronjobs,versions=v1,name=vcronjob.kb.io

var _ webhook.Validator = &CronJob{}

// ValidateCreate implements webhook.Validator so a webhook will be registered for the type
func (r *CronJob) ValidateCreate() error {
	cronjoblog.Info("validate create", "name", r.Name)

	return r.validateCronJob()
}

// ValidateUpdate implements webhook.Validator so a webhook will be registered for the type
func (r *CronJob) ValidateUpdate(old runtime.Object) error {
	cronjoblog.Info("validate update", "name", r.Name)

	return r.validateCronJob()
}

// ValidateDelete implements webhook.Validator so a webhook will be registered for the type
func (r *CronJob) ValidateDelete() error {
	cronjoblog.Info("validate delete", "name", r.Name)

	// TODO(user): fill in your validation logic upon object deletion.
	return nil
}

func (r *CronJob) validateCronJob() error {
	var allErrs field.ErrorList
	if err := r.validateCronJobName(); err != nil {
		allErrs = append(allErrs, err)
	}
	if err := r.validateCronJobSpec(); err != nil {
		allErrs = append(allErrs, err)
	}
	if len(allErrs) == 0 {
		return nil
	}

	return apierrors.NewInvalid(
		schema.GroupKind{Group: "batch.tutorial.kubebuilder.io", Kind: "CronJob"},
		r.Name, allErrs)
}

func (r *CronJob) validateCronJobSpec() *field.Error {
	// The field helpers from the kubernetes API machinery help us return nicely
	// structured validation errors.
	return validateScheduleFormat(
		r.Spec.Schedule,
		field.NewPath("spec").Child("schedule"))
}

func validateScheduleFormat(schedule string, fldPath *field.Path) *field.Error {
	if _, err := cron.ParseStandard(schedule); err != nil {
		return field.Invalid(fldPath, schedule, err.Error())
	}
	return nil
}

func (r *CronJob) validateCronJobName() *field.Error {
	if len(r.ObjectMeta.Name) > validationutils.DNS1035LabelMaxLength-11 {
		// The job name length is 63 character like all Kubernetes objects
		// (which must fit in a DNS subdomain). The cronjob controller appends
		// a 11-character suffix to the cronjob (`-$TIMESTAMP`) when creating
		// a job. The job name length limit is 63 characters. Therefore cronjob
		// names must have length <= 63-11=52. If we don't validate this here,
		// then job creation will fail later.
		return field.Invalid(field.NewPath("metadata").Child("name"), r.Name, "must be no more than 52 characters")
	}
	return nil
}

...and main.go

Similarly, our existing main file is sufficient:

project/main.go
Apache License

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

http://www.apache.org/licenses/LICENSE-2.0

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.

Imports
package main

import (
	"flag"
	"os"

	kbatchv1 "k8s.io/api/batch/v1"
	"k8s.io/apimachinery/pkg/runtime"
	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/log/zap"
	batchv1 "tutorial.kubebuilder.io/project/api/v1"
	batchv2 "tutorial.kubebuilder.io/project/api/v2"
	"tutorial.kubebuilder.io/project/controllers"
	// +kubebuilder:scaffold:imports
)
existing setup
var (
	scheme   = runtime.NewScheme()
	setupLog = ctrl.Log.WithName("setup")
)

func init() {
	_ = clientgoscheme.AddToScheme(scheme)

	_ = kbatchv1.AddToScheme(scheme) // we've added this ourselves
	_ = batchv1.AddToScheme(scheme)
	_ = batchv2.AddToScheme(scheme)
	// +kubebuilder:scaffold:scheme
}
func main() {
existing setup
	var metricsAddr string
	var enableLeaderElection bool
	flag.StringVar(&metricsAddr, "metrics-addr", ":8080", "The address the metric endpoint binds to.")
	flag.BoolVar(&enableLeaderElection, "enable-leader-election", false,
		"Enable leader election for controller manager. Enabling this will ensure there is only one active controller manager.")
	flag.Parse()

	ctrl.SetLogger(zap.Logger(true))

	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
		Scheme:             scheme,
		MetricsBindAddress: metricsAddr,
		LeaderElection:     enableLeaderElection,
	})
	if err != nil {
		setupLog.Error(err, "unable to start manager")
		os.Exit(1)
	}

	if err = (&controllers.CronJobReconciler{
		Client: mgr.GetClient(),
		Log:    ctrl.Log.WithName("controllers").WithName("Captain"),
		Scheme: mgr.GetScheme(), // we've added this ourselves
	}).SetupWithManager(mgr); err != nil {
		setupLog.Error(err, "unable to create controller", "controller", "Captain")
		os.Exit(1)
	}

Our existing call to SetupWebhookWithManager registers our conversion webhooks with the manager, too.

	if err = (&batchv1.CronJob{}).SetupWebhookWithManager(mgr); err != nil {
		setupLog.Error(err, "unable to create webhook", "webhook", "Captain")
		os.Exit(1)
	}
	// +kubebuilder:scaffold:builder
existing setup
	setupLog.Info("starting manager")
	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
		setupLog.Error(err, "problem running manager")
		os.Exit(1)
	}
}

Everything’s set up and ready to go! All that’s left now is to test out our webhooks.