走剧情的NPC

在前面的文章 Kubernetes中基于二层的负载均衡实现 有提到过使用 leader 选举来实现高可用，下面是对应的参考代码

package main

import (
	"context"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/golang/glog"
	"github.com/google/uuid"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/informers"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/leaderelection"
	"k8s.io/client-go/tools/leaderelection/resourcelock"
)

func main() {
	defer glog.Flush()

	// 当前 pod 运行的 namespace，推荐从 downward api 读取
	namespace := "default"

	// 使用随机生成的 uuid，也可以使用 pod_name 作为注册的唯一标识
	uuid, _ := uuid.NewUUID()
	id := uuid.String()

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	config, err := rest.InClusterConfig()
	client := kubernetes.NewForConfigOrDie(config)

	stop := make(chan struct{})
	stopCh := make(chan os.Signal, 1)
	signal.Notify(stopCh, os.Interrupt, syscall.SIGTERM)
	go func() {
		<-stopCh
		glog.Info("Received termination, signaling shutdown")
		close(stop)
		cancel()
	}()

	run := func(ctx context.Context, stop <-chan struct{}) {
		sharedInformerFactory := informers.NewSharedInformerFactory(client, 5*time.Minute)
		//    业务相关

		glog.Infof("start shared informer factory")
		sharedInformerFactory.Start(stop)

		<-stopCh
	}

	// 创建一个资源锁
	lock := &resourcelock.LeaseLock{
		LeaseMeta: metav1.ObjectMeta{
			Name:      "app-xxx-lockname",
			Namespace: namespace,
		},
		Client: client.CoordinationV1(),
		LockConfig: resourcelock.ResourceLockConfig{
			Identity: id,
		},
	}

	// 开启一个选举的循环
	leaderelection.RunOrDie(ctx, leaderelection.LeaderElectionConfig{
		Lock:            lock,
		ReleaseOnCancel: true,
		LeaseDuration:   60 * time.Second,
		RenewDeadline:   15 * time.Second,
		RetryPeriod:     5 * time.Second,
		Callbacks: leaderelection.LeaderCallbacks{
			OnStartedLeading: func(ctx context.Context) {
				// 当选举为leader后所运行的业务逻辑
				run(ctx, stop)
			},
			OnStoppedLeading: func() {
				// we can do cleanup here
				glog.Infof("leader lost: %s", id)
				os.Exit(0)
			},
			OnNewLeader: func(identity string) { // 申请一个选举时的动作
				if identity == id {
					return
				}
				glog.Infof("new leader elected: %s", identity)
			},
		},
	})
}