kubebuilder mutating webhook

main.go

/*
Copyright 2022 fl64 <[email protected]>.
*/

package main

import (
	"flag"
	"github.com/fl64/gitlab-job-mutator/mutator"
	"os"
	"sigs.k8s.io/controller-runtime/pkg/webhook"

	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
	// to ensure that exec-entrypoint and run can make use of them.
	_ "k8s.io/client-go/plugin/pkg/client/auth"

	"k8s.io/apimachinery/pkg/runtime"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/healthz"
	"sigs.k8s.io/controller-runtime/pkg/log/zap"
	//+kubebuilder:scaffold:imports
)

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

func init() {
	utilruntime.Must(clientgoscheme.AddToScheme(scheme))

	//+kubebuilder:scaffold:scheme
}

func main() {
	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,
	}
	opts.BindFlags(flag.CommandLine)
	flag.Parse()

	ctrl.SetLogger(zap.New(zap.UseFlagOptions(&opts)))

	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
		Scheme:                 scheme,
		MetricsBindAddress:     metricsAddr,
		Port:                   9443,
		HealthProbeBindAddress: probeAddr,
		LeaderElection:         enableLeaderElection,
		LeaderElectionID:       "e3ba4979.fl64.net",
	})
	if err != nil {
		setupLog.Error(err, "unable to start manager")
		os.Exit(1)
	}

	mutator := &mutator.PodMutator{
		Client: mgr.GetClient(),
	}
	setupLog.Info("Register webhook")
	mgr.GetWebhookServer().Register("/mutate-core-v1-pod", &webhook.Admission{Handler: mutator})
	setupLog.Info("Register finished")
	//+kubebuilder:scaffold:builder

	if err := mgr.AddHealthzCheck("healthz", healthz.Ping); err != nil {
		setupLog.Error(err, "unable to set up health check")
		os.Exit(1)
	}
	if err := mgr.AddReadyzCheck("readyz", healthz.Ping); err != nil {
		setupLog.Error(err, "unable to set up ready check")
		os.Exit(1)
	}

	setupLog.Info("starting manager")
	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
		setupLog.Error(err, "problem running manager")
		os.Exit(1)
	}
}

mutator.go

/*
Copyright 2022 fl64 <[email protected]>.
*/

package mutator

import (
	"context"
	"encoding/json"
	corev1 "k8s.io/api/core/v1"
	"net/http"
	"sigs.k8s.io/controller-runtime/pkg/client"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
)

// log is for logging in this package.
var podlog = logf.Log.WithName("pod-resource")

// TODO(user): EDIT THIS FILE!  THIS IS SCAFFOLDING FOR YOU TO OWN!

//+kubebuilder:webhook:path=/mutate-core-v1-pod,mutating=true,failurePolicy=fail,sideEffects=None,groups=core,resources=pods,verbs=create;update,versions=v1,name=mpod.kb.io,admissionReviewVersions=v1
type PodMutator struct {
	Client  client.Client
	decoder *admission.Decoder
}

func (p *PodMutator) Handle(ctx context.Context, req admission.Request) admission.Response {
	podlog.Info("Start mutator")
	pod := &corev1.Pod{}
	err := p.decoder.Decode(req, pod)
	if err != nil {
		return admission.Errored(http.StatusBadRequest, err)
	}
	sidecar := corev1.Container{
		Name:            "nginx",
		Image:           "nginx:1.16",
		ImagePullPolicy: corev1.PullIfNotPresent,
		Ports: []corev1.ContainerPort{
			{
				Name:          "http",
				ContainerPort: 80,
			},
		},
	}
	pod.Spec.Containers = append(pod.Spec.Containers, sidecar)
	marshaledPod, err := json.Marshal(pod)
	if err != nil {
		return admission.Errored(http.StatusInternalServerError, err)
	}
	return admission.PatchResponseFromRaw(req.Object.Raw, marshaledPod)
}

func (p *PodMutator) InjectDecoder(d *admission.Decoder) error {
	p.decoder = d
	return nil
}