1. 操作ETCD
这里使用官方的etcd/clientv3包来连接etcd并进行相关操作。
1.1.1. 安装
go get go.etcd.io/etcd/clientv3
1.1.2. put和get操作
put命令用来设置键值对数据，get命令用来根据key获取值。
package main
import (
"context"
"fmt"
"time"
"go.etcd.io/etcd/clientv3"
)
// etcd client put/get demo
// use etcd/clientv3
func main() {
cli, err := clientv3.New(clientv3.Config{
Endpoints: []string{"127.0.0.1:2379"},
DialTimeout: 5 * time.Second,
})
if err != nil {
// handle error!
fmt.Printf("connect to etcd failed, err:%v\n", err)
return
}
fmt.Println("connect to etcd success")
defer cli.Close()
// put
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
_, err = cli.Put(ctx, "lmh", "lmh")
cancel()
if err != nil {
fmt.Printf("put to etcd failed, err:%v\n", err)
return
}
// get
ctx, cancel = context.WithTimeout(context.Background(), time.Second)
resp, err := cli.Get(ctx, "lmh")
cancel()
if err != nil {
fmt.Printf("get from etcd failed, err:%v\n", err)
return
}
for _, ev := range resp.Kvs {
fmt.Printf("%s:%s\n", ev.Key, ev.Value)
}
}
1.1.3. watch操作
watch用来获取未来更改的通知。
package main
import (
"context"
"fmt"
"time"
"go.etcd.io/etcd/clientv3"
)
// watch demo
func main() {
cli, err := clientv3.New(clientv3.Config{
Endpoints: []string{"127.0.0.1:2379"},
DialTimeout: 5 * time.Second,
})
if err != nil {
fmt.Printf("connect to etcd failed, err:%v\n", err)
return
}
fmt.Println("connect to etcd success")
defer cli.Close()
// watch key:lmh change
rch := cli.Watch(context.Background(), "lmh") // <-chan WatchResponse
for wresp := range rch {
for _, ev := range wresp.Events {
fmt.Printf("Type: %s Key:%s Value:%s\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
}
}
}
将上面的代码保存编译执行，此时程序就会等待etcd中lmh这个key的变化。
例如：我们打开终端执行以下命令修改、删除、设置lmh这个key。
etcd> etcdctl.exe --endpoints=http://127.0.0.1:2379 put lmh "lmh1"
OK
etcd> etcdctl.exe --endpoints=http://127.0.0.1:2379 del lmh
1
etcd> etcdctl.exe --endpoints=http://127.0.0.1:2379 put lmh "lmh2"
OK
上面的程序都能收到如下通知。
watch>watch.exe
connect to etcd success
Type: PUT Key:lmh Value:lmh1
Type: DELETE Key:lmh Value:
Type: PUT Key:lmh Value:lmh2
1.1.4. lease租约
package main
import (
"fmt"
"time"
)
// etcd lease
import (
"context"
"log"
"go.etcd.io/etcd/clientv3"
)
func main() {
cli, err := clientv3.New(clientv3.Config{
Endpoints: []string{"127.0.0.1:2379"},
DialTimeout: time.Second * 5,
})
if err != nil {
log.Fatal(err)
}
fmt.Println("connect to etcd success.")
defer cli.Close()
// 创建一个5秒的租约
resp, err := cli.Grant(context.TODO(), 5)
if err != nil {
log.Fatal(err)
}
// 5秒钟之后, /lmh/ 这个key就会被移除
_, err = cli.Put(context.TODO(), "/lmh/", "lmh", clientv3.WithLease(resp.ID))
if err != nil {
log.Fatal(err)
}
}
1.1.5. keepAlive
package main
import (
"context"
"fmt"
"log"
"time"
"go.etcd.io/etcd/clientv3"
)
// etcd keepAlive
func main() {
cli, err := clientv3.New(clientv3.Config{
Endpoints: []string{"127.0.0.1:2379"},
DialTimeout: time.Second * 5,
})
if err != nil {
log.Fatal(err)
}
fmt.Println("connect to etcd success.")
defer cli.Close()
resp, err := cli.Grant(context.TODO(), 5)
if err != nil {
log.Fatal(err)
}
_, err = cli.Put(context.TODO(), "/lmh/", "lmh", clientv3.WithLease(resp.ID))
if err != nil {
log.Fatal(err)
}
// the key 'foo' will be kept forever
ch, kaerr := cli.KeepAlive(context.TODO(), resp.ID)
if kaerr != nil {
log.Fatal(kaerr)
}
for {
ka := <-ch
fmt.Println("ttl:", ka.TTL)
}
}
1.1.6. 基于etcd实现分布式锁
go.etcd.io/etcd/clientv3/concurrency在etcd之上实现并发操作，如分布式锁、屏障和选举。
导入该包：
import "go.etcd.io/etcd/clientv3/concurrency"
基于etcd实现的分布式锁示例：
cli, err := clientv3.New(clientv3.Config{Endpoints: endpoints})
if err != nil {
log.Fatal(err)
}
defer cli.Close()
// 创建两个单独的会话用来演示锁竞争
s1, err := concurrency.NewSession(cli)
if err != nil {
log.Fatal(err)
}
defer s1.Close()
m1 := concurrency.NewMutex(s1, "/my-lock/")
s2, err := concurrency.NewSession(cli)
if err != nil {
log.Fatal(err)
}
defer s2.Close()
m2 := concurrency.NewMutex(s2, "/my-lock/")
// 会话s1获取锁
if err := m1.Lock(context.TODO()); err != nil {
log.Fatal(err)
}
fmt.Println("acquired lock for s1")
m2Locked := make(chan struct{})
go func() {
defer close(m2Locked)
// 等待直到会话s1释放了/my-lock/的锁
if err := m2.Lock(context.TODO()); err != nil {
log.Fatal(err)
}
}()
if err := m1.Unlock(context.TODO()); err != nil {
log.Fatal(err)
}
fmt.Println("released lock for s1")
<-m2Locked
fmt.Println("acquired lock for s2")
输出：
acquired lock for s1
released lock for s1
acquired lock for s2