CRD watcher using dyamic client ( not using queue ds )

main.go

package main

import (
	"os"
	"os/signal"

	"github.com/sirupsen/logrus"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/dynamic/dynamicinformer"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/clientcmd"
)

func main() {
	cfg, err := restConfig()
	if err != nil {
		logrus.WithError(err).Fatal("could not get config")
	}

	dc, err := dynamic.NewForConfig(cfg)
	if err != nil {
		logrus.WithError(err).Fatal("could not generate dynamic client for config")
	}

	virtualServiceGVR := crd("zookeeper.pravega.io", "v1beta1", "zookeeperclusters")

	f := dynamicinformer.NewFilteredDynamicSharedInformerFactory(dc, 0, "druid", nil)

	i := f.ForResource(virtualServiceGVR)

	stopCh := make(chan struct{})
	go startWatching(stopCh, i.Informer())

	sigCh := make(chan os.Signal, 0)
	signal.Notify(sigCh, os.Kill, os.Interrupt)

	<-sigCh
	close(stopCh)
}

func restConfig() (*rest.Config, error) {
	kubeCfg, err := rest.InClusterConfig()
	if kubeconfig := os.Getenv("KUBECONFIG"); kubeconfig != "" {
		kubeCfg, err = clientcmd.BuildConfigFromFlags("", kubeconfig)
	}

	if err != nil {
		return nil, err
	}

	return kubeCfg, nil
}

func startWatching(stopCh <-chan struct{}, s cache.SharedIndexInformer) {
	handlers := cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			u := obj.(*unstructured.Unstructured)

			logrus.WithFields(logrus.Fields{
				"name":      u.GetName(),
				"namespace": u.GetNamespace(),
				"labels":    u.GetLabels(),
			}).Info("received add event!")
		},
		UpdateFunc: func(oldObj, obj interface{}) {
			logrus.Info("received update event!")
		},
		DeleteFunc: func(obj interface{}) {
			logrus.Info("received delete event!")
		},
	}

	s.AddEventHandler(handlers)
	s.Run(stopCh)
}

func crd(group, version, resource string) schema.GroupVersionResource {
	return schema.GroupVersionResource{
		Group:    group,
		Version:  version,
		Resource: resource,
	}
}