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| package main
import (
"context"
"flag"
"fmt"
"os"
"os/signal"
"syscall"
"time"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
clientset "k8s.io/client-go/kubernetes"
"k8s.io/client-go/rest"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/tools/leaderelection"
"k8s.io/client-go/tools/leaderelection/resourcelock"
"k8s.io/klog/v2"
)
func buildConfig(kubeconfig string) (*rest.Config, error) {
if kubeconfig != "" {
cfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
if err != nil {
return nil, err
}
return cfg, nil
}
cfg, err := rest.InClusterConfig()
if err != nil {
return nil, err
}
return cfg, nil
}
func main() {
klog.InitFlags(nil)
var kubeconfig string
var leaseLockName string
var leaseLockNamespace string
var id string
// 初始化客户端的部分
flag.StringVar(&kubeconfig, "kubeconfig", "", "absolute path to the kubeconfig file")
flag.StringVar(&id, "id", "", "the holder identity name")
flag.StringVar(&leaseLockName, "lease-lock-name", "", "the lease lock resource name")
flag.StringVar(&leaseLockNamespace, "lease-lock-namespace", "", "the lease lock resource namespace")
flag.Parse()
if leaseLockName == "" {
klog.Fatal("unable to get lease lock resource name (missing lease-lock-name flag).")
}
if leaseLockNamespace == "" {
klog.Fatal("unable to get lease lock resource namespace (missing lease-lock-namespace flag).")
}
config, err := buildConfig(kubeconfig)
if err != nil {
klog.Fatal(err)
}
client := clientset.NewForConfigOrDie(config)
run := func(ctx context.Context) {
// 实现的业务逻辑，这里仅仅为实验，就直接打印了
klog.Info("Controller loop...")
for {
fmt.Println("I am leader, I was working.")
time.Sleep(time.Second * 5)
}
}
// use a Go context so we can tell the leaderelection code when we
// want to step down
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
// 监听系统中断
ch := make(chan os.Signal, 1)
signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
go func() {
<-ch
klog.Info("Received termination, signaling shutdown")
cancel()
}()
// 创建一个资源锁
lock := &resourcelock.LeaseLock{
LeaseMeta: metav1.ObjectMeta{
Name: leaseLockName,
Namespace: leaseLockNamespace,
},
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)
},
OnStoppedLeading: func() {
// we can do cleanup here
klog.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
}
klog.Infof("new leader elected: %s", identity)
},
},
})
}
|