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/*
例子来源于client-go中的example包中
*/
package main
import (
"context"
"flag"
"os"
"os/signal"
"syscall"
"time"
"github.com/google/uuid"
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"
)
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
flag.StringVar(&kubeconfig, "kubeconfig", "", "absolute path to the kubeconfig file")
flag.StringVar(&id, "id", uuid.New().String(), "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).")
}
// leader election uses the Kubernetes API by writing to a
// lock object, which can be a LeaseLock object (preferred),
// a ConfigMap, or an Endpoints (deprecated) object.
// Conflicting writes are detected and each client handles those actions
// independently.
config, err := buildConfig(kubeconfig)
if err != nil {
klog.Fatal(err)
}
client := clientset.NewForConfigOrDie(config)
run := func(ctx context.Context) {
// complete your controller loop here
klog.Info("Controller loop...")
select {}
}
// 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()
// listen for interrupts or the Linux SIGTERM signal and cancel
// our context, which the leader election code will observe and
// step down
ch := make(chan os.Signal, 1)
signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
go func() {
<-ch
klog.Info("Received termination, signaling shutdown")
cancel()
}()
// we use the Lease lock type since edits to Leases are less common
// and fewer objects in the cluster watch "all Leases".
// 指定锁的资源对象，这里使用了Lease资源，还支持configmap，endpoint，或者multilock(即多种配合使用)
lock := &resourcelock.LeaseLock{
LeaseMeta: metav1.ObjectMeta{
Name: leaseLockName,
Namespace: leaseLockNamespace,
},
Client: client.CoordinationV1(),
LockConfig: resourcelock.ResourceLockConfig{
Identity: id,
},
}
// start the leader election code loop
leaderelection.RunOrDie(ctx, leaderelection.LeaderElectionConfig{
Lock: lock,
// IMPORTANT: you MUST ensure that any code you have that
// is protected by the lease must terminate **before**
// you call cancel. Otherwise, you could have a background
// loop still running and another process could
// get elected before your background loop finished, violating
// the stated goal of the lease.
ReleaseOnCancel: true,
LeaseDuration: 60 * time.Second,//租约时间
RenewDeadline: 15 * time.Second,//更新租约的
RetryPeriod: 5 * time.Second,//非leader节点重试时间
Callbacks: leaderelection.LeaderCallbacks{
OnStartedLeading: func(ctx context.Context) {
//变为leader执行的业务代码
// we're notified when we start - this is where you would
// usually put your code
run(ctx)
},
OnStoppedLeading: func() {
// 进程退出
// we can do cleanup here
klog.Infof("leader lost: %s", id)
os.Exit(0)
},
OnNewLeader: func(identity string) {
//当产生新的leader后执行的方法
// we're notified when new leader elected
if identity == id {
// I just got the lock
return
}
klog.Infof("new leader elected: %s", identity)
},
},
})
}
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