dynamic informers example code. 원본: https://github.com/cloud-native-skunkworks/dynamic-informer

main.go

package main

import (
	"log"
	"os"
	"time"

	"github.com/open-feature/open-feature-operator/apis/core/v1alpha1"
	"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 buildConfiguration() (*rest.Config, error) {
	kubeconfig := os.Getenv("KUBECONFIG")
	var clusterConfig *rest.Config
	var err error
	if kubeconfig != "" {
		clusterConfig, err = clientcmd.BuildConfigFromFlags("", kubeconfig)
	} else {
		clusterConfig, err = rest.InClusterConfig()
	}
	if err != nil {
		return nil, err
	}

	return clusterConfig, nil
}

func main() {
	clusterConfig, err := buildConfiguration()
	if err != nil {
		panic(err)
	}
	// traditional k8s client 대신 dynamic 패키지 사용.
	clusterClient, err := dynamic.NewForConfig(clusterConfig)
	if err != nil {
		log.Fatalln(err)
	}
	// CRD operator에서 제공하는 Resource 정보.
	resource := v1alpha1.GroupVersion.WithResource("featureflagconfigurations")
	// shared Informer factory 생성. look at several different clsuter resources simultaneously.
	//// resync time: cache between listing.
	factory := dynamicinformer.NewFilteredDynamicSharedInformerFactory(clusterClient,
		time.Minute, "", nil)

	informer := factory.ForResource(resource).Informer()

	// event handler 추가.
	informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			log.Println("AddFunc")
		},
		UpdateFunc: func(oldObj, newObj interface{}) {
			log.Println("UpdateFunc")
			// 이벤트 발생했을 때 interface{}를 필요한 리소스로 매핑하는 형태로 사용 가능.
			// ex)
			// var featureflagObject v1alpha1.FeatureFlagConfiguration
			//err := runtime.DefaultUnstructuredConverter.FromUnstructured(newObj, (*unstructured.Unstructured).Object, &featureflagObject)
			// if err != nil {
			//  	log.Println(err.Error())
			// }
		},
		DeleteFunc: func(obj interface{}) {
			log.Println("DeleteFunc")
		},
	})
	
	// informer에 context를 추가하거나 inline channel을 넣는다.
	
	informer.Run(make(chan struct{}))
}