etcd入门

​ etcd是分布式协调框架，基本和zookeeper功能和场景相似。它使用高可用的k-v键值对做数据库，采用raft一致性算法。采用Go语言实现。

​ etcd使用gRPC对外提供API。总共分为三类

• Kv:key-value的创建、更新、读取和删除
• watch：提供监控数据更新的机制
• Lease ：用来支持客户端的keep-alive的消息 可以设置lease和key进行绑定，当lease释放后，key就会被删除，相当于zk中的临时性节点

etcd本地安装

Mac : etcd-v3.4.13-darwin-amd64.zip

linux: etcd-v3.4.13-linux-amd64.tar.gz

Windows: etcd-v3.4.13-windows-amd64.zip

下载后解压即可

etcd启动

cd "解压目录"
etcd # 启动etcd standalone
etcdctl # etcd控制的工具
etcdctl put foo value1
etcdctl get foo

Go连接etcd并使用v3Client操作etcd

package main

import (
	"context"
	"fmt"
	"go.etcd.io/etcd/clientv3"
	"time"
)

func main() {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   []string{"localhost:2379"},
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		fmt.Println("failed to create client")
	}
	defer cli.Close()
	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
	resp, err := cli.Put(ctx, "cpf", "zzc1")
	cancel()
	if err != nil {
		fmt.Println("failed to put")
	}
	// use the response
	fmt.Println("resp", resp)
}
module declares its path as: go.etcd.io/bbolt
	        but was required as: github.com/coreos/bbolt

使用etcd v3Client可能遇到几个问题：

1. module declares its path as: go.etcd.io/bbolt but was required as: github.com/coreos/bbolt(包依赖冲突)

   replace github.com/coreos/bbolt v1.3.5 => go.etcd.io/bbolt v1.3.5
   
   replace go.etcd.io/bbolt v1.3.5 => github.com/coreos/bbolt v1.3.5

2. etcd undefined: resolver.BuildOption (版本依赖冲突)

   go mod edit -require=google.golang.org/[email protected]
   go get -u -x google.golang.org/[email protected]
   go build