golang基于etcd做分布式任务锁

Posted 2021-12-12 chmyee

参考：https://www.jianshu.com/p/d7434d916856

etcd服务搭建请看上一篇，下面直接上代码：

# go get github.com/etcd-io/etcd

main.go 内容如下：

package main

import (
   "context"
   "fmt"
   "time"
   //"github.com/etcd-io/etcd/clientv3" 这个引用会导致启动失败
   "go.etcd.io/etcd/clientv3"
)

//锁结构体
type EtcdMutex struct {
   Ttl int64  //租约时间
   Conf clientv3.Config  //etcd集群配置
   Key string   //etcd的key
   cancel context.CancelFunc  //关闭续租的func
   lease clientv3.Lease
   leaseID clientv3.LeaseID
   txn clientv3.Txn
}

//初始化锁
func (em *EtcdMutex) init() error {
   var err error
   var ctx context.Context
   client,err := clientv3.New(em.Conf)
   if err != nil{
      return err
   }
   em.txn = clientv3.NewKV(client).Txn(context.TODO())
   em.lease = clientv3.NewLease(client)
   leaseResp,err := em.lease.Grant(context.TODO(),em.Ttl)
   if err != nil{
      return err
   }
   ctx,em.cancel = context.WithCancel(context.TODO())
   em.leaseID = leaseResp.ID
   _,err = em.lease.KeepAlive(ctx,em.leaseID)
   return err
}

//获取锁
func (em *EtcdMutex) Lock() error {
   err := em.init()
   if err != nil{
      return err
   }
   //LOCK:
   em.txn.If(clientv3.Compare(clientv3.CreateRevision(em.Key),"=",0)).
      Then(clientv3.OpPut(em.Key,"",clientv3.WithLease(em.leaseID))).
      Else()
   txnResp,err := em.txn.Commit()
   if err != nil{
      return err
   }
   if !txnResp.Succeeded{   //判断txn.if条件是否成立
      return fmt.Errorf("抢锁失败")
   }
   return nil
}

//释放锁
func(em *EtcdMutex) UnLock() {
   em.cancel()
   em.lease.Revoke(context.TODO(),em.leaseID)
   fmt.Println("释放了锁")
}

func EtcdTest()  {
   fmt.Println("start etcd connect ...")
   var conf = clientv3.Config{
      Endpoints:   []string{"172.16.4.67:2379"},
      DialTimeout: 5 * time.Second,
   }
   eMutex1 := &EtcdMutex{
      Conf:conf,
      Ttl:10,
      Key:"lock",
   }
   eMutex2 := &EtcdMutex{
      Conf:conf,
      Ttl:10,
      Key:"lock",
   }
   //groutine1
   go func() {
      fmt.Println("groutine1")
      err := eMutex1.Lock()
      fmt.Println(err)
      if err != nil {
         fmt.Println("groutine1抢锁失败")
         fmt.Println(err)
         return
      }
      fmt.Println("groutine1抢锁成功")
      time.Sleep(10*time.Second)
      defer eMutex1.UnLock()
   }()

   //groutine2
   go func() {
      fmt.Println("groutine2")
      err := eMutex2.Lock()
      fmt.Println(err)
      if err != nil {
         fmt.Println("groutine2抢锁失败")
         fmt.Println(err)
         return
      }
      fmt.Println("groutine2抢锁成功")
      defer eMutex2.UnLock()
   }()
   time.Sleep(300*time.Second)
}

程序输出如下：