Go Etcd

官网：

https://etcd.io/docs/v3.5/quickstart/

https://github.com/etcd-io/etcd

etcd 是什么

• etcd是一种key-value存储, 它侧重于保证集群环境中数据的一致性
• redis也是键值对存储, 它侧重于提供高速读写. 当需要在集群中保证数据强一致的时候就用etcd.

etcd是使用Go语言开发的一个开源的、高可用的分布式key-value存储系统，可以用于配置共享和服务的注册和发现。

特点

完全复制：集群中的每个节点都可以使用完整的存档
高可用性：Etcd可用于避免硬件的单点故障或网络问题
一致性：每次读取都会返回跨多主机的最新写入
简单：包括一个定义良好、面向用户的API(gRpc）
安全：实现了带有可选的客户端证书身份验证的自动化TLS
快速：每秒10000次写入的基准速度
可靠：使用Raft算法实现了强一致、高可用的服务存储目录

应用

服务发现

服务发现就是想要了解集群中是否有进程在监听 udp 或 tcp 端口，并且通过名字就可以查找和连接。

配置中心

将一些配置信息放到 etcd 上进行集中管理。

应用在启动的时候主动从 etcd 获取一次配置信息，

同时，在 etcd 节点上注册一个 Watcher 并等待，

以后每次配置有更新的时候，etcd 都会实时通知订阅者，以此达到获取最新配置信息的目的。

Etcd 安装3.5

去官网找一遍发现，居然没有docker 安装方式？what ？我看错了？

聪明的你们快去找找，https://etcd.io/docs/v3.5/install/

官网上只有：

• 二进制文件安装
• 从源码构建go

两种方式

那这个，我们创建一个docker镜像吧，因为我的最终目的是用docker模拟集群环境

创建go容器

hub 中有 golang 镜像，可以直接拉取：

docker pull golang

拉取到的镜像是基于 debian(linux 发行版的一种) 制作。

创建三个容器：

# 这个容器暴露端口给外部使用
docker run -itd -p 22379:2379 --name etcd1 golang
docker run -itd --name etcd2 golang
docker run -itd --name etcd3 golang

查看go版本

go version

在每个容器中 clone etcd

打开三个终端

docker exec -it etcd1 bash
docker exec -it etcd2 bash
docker exec -it etcd3 bash

在每个容器中克隆：

# 最新的3.6版本,需要go 1.19 这个容器
git clone https://github.com/etcd-io/etcd.git
# etcd 3.5版本 go 1.17.5 能编译通过，我用的就是这个
git clone -b v3.5.0 https://github.com/etcd-io/etcd.git

编绎 etcd

编绎脚本会拉取一些 golang 库，所以先设置好 goproxy 是非常有必要的。

go env -w GO111MODULE=on
go env -w GOPROXY=https://goproxy.cn,direct

在每个容器中都需要执行下面的命令。

cd etcd
./build.sh

编绎完成后，会多一个 bin 目录，里面有两个可执行文件etcd和etcdctl，分别为服务端和客户端文件，搭建集群，使用的是etcd。

保证三个容器之间网络畅通

有关docker 网络可以参考：

https://www.cnblogs.com/makalochen/p/14242125.html

我们在写etcd 的配置文件之前我们得知道，对应etcd节点的IP已经各个节点之间是否可以互相访问

查询容器三个容器的ip

# 查询正在运行的容器，得到容器id
docker ps

# 查询对应容器的ip
# docker inspect --format '{{ .NetworkSettings.IPAddress }}' 容器id1 容器id2
docker inspect --format '{{ .NetworkSettings.IPAddress }}' 1080bf1030f6 f2a07b90daa1 24db14135e82

# 因为我们创建容器并没有指定网络，所以默认加入 bridge
# 查看是否已经加入
docker network inspect bridge

由上图可以得知，这三个容器在同一个网络中，他们网络访问应该没有问题，由于该容器中并没有ping工具，所以我就不测试了，应该是没啥问题

写配置文件

etcd 的目录中有一个etcd.conf.yml.sample是示例配置文件，将其复制一份用来作待使用的配置文件：

cp etcd.conf.yml.sample etcd.conf.yml

因为容器里面没有vi等工具，所以为了方便我用vscode 装 docker 扩展修改文件

修改配置文件，下面只列出配置文件中需要修改的部分：

# 节点别名，给人类看的
name: 'etcd3'

# 数据文件存放的目录
data-dir: /var/lib/etcd

# 用逗号分隔的 url 列表，用于与其他节点通信  
# 下面 172.17.0.4 是docker 容器ip,每个节点不一样 注意修改，只能一个不能用逗号分隔多个
listen-peer-urls: http://172.17.0.4:2380

# 用逗号分隔的 url 列表，用于与客户端通信
listen-client-urls: http://172.17.0.4:2379,http://localhost:2379

# 用逗号分隔的 url 列表，用于通知其他节点，与通信端口相同即可，只能一个不能用逗号分隔多个
initial-advertise-peer-urls: http://172.17.0.4:2380

# 用逗号分隔的 url 列表，用于公开通知客户端，只能一个不能用逗号分隔多个
advertise-client-urls: http://172.17.0.4:2379

# 初始化集群配置。集群各节点别名与其 url 的键值对列表
initial-cluster: infra1=http://172.17.0.2:2380,infra2=http://172.17.0.3:2380,infra3=http://172.17.0.4:2380

# 初始化集群 token , 每个节点配置成一样
initial-cluster-token: 'etcd-cluster-1'

Etcd1 的配置文件

# This is the configuration file for the etcd server.

# Human-readable name for this member.
name: 'etcd1'

# Path to the data directory.
data-dir: /var/lib/etcd

# Path to the dedicated wal directory.
wal-dir:

# Number of committed transactions to trigger a snapshot to disk.
snapshot-count: 10000

# Time (in milliseconds) of a heartbeat interval.
heartbeat-interval: 100

# Time (in milliseconds) for an election to timeout.
election-timeout: 1000

# Raise alarms when backend size exceeds the given quota. 0 means use the
# default quota.
quota-backend-bytes: 0

# List of comma separated URLs to listen on for peer traffic.
listen-peer-urls: http://172.17.0.2:2380

# List of comma separated URLs to listen on for client traffic.
listen-client-urls: http://172.17.0.2:2379,http://localhost:2379

# Maximum number of snapshot files to retain (0 is unlimited).
max-snapshots: 5

# Maximum number of wal files to retain (0 is unlimited).
max-wals: 5

# Comma-separated white list of origins for CORS (cross-origin resource sharing).
cors:

# List of this member's peer URLs to advertise to the rest of the cluster.
# The URLs needed to be a comma-separated list.
initial-advertise-peer-urls: http://172.17.0.2:2380

# List of this member's client URLs to advertise to the public.
# The URLs needed to be a comma-separated list.
advertise-client-urls: http://172.17.0.2:2379

# Discovery URL used to bootstrap the cluster.
discovery:

# Valid values include 'exit', 'proxy'
discovery-fallback: 'proxy'

# HTTP proxy to use for traffic to discovery service.
discovery-proxy:

# DNS domain used to bootstrap initial cluster.
discovery-srv:

# Initial cluster configuration for bootstrapping.
initial-cluster: etcd1=http://172.17.0.2:2380,etcd2=http://172.17.0.3:2380,etcd3=http://172.17.0.4:2380

# Initial cluster token for the etcd cluster during bootstrap.
initial-cluster-token: 'etcd-cluster1'

# Initial cluster state ('new' or 'existing').
initial-cluster-state: 'new'

# Reject reconfiguration requests that would cause quorum loss.
strict-reconfig-check: false

# Accept etcd V2 client requests
enable-v2: true

# Enable runtime profiling data via HTTP server
enable-pprof: true

# Valid values include 'on', 'readonly', 'off'
proxy: 'off'

# Time (in milliseconds) an endpoint will be held in a failed state.
proxy-failure-wait: 5000

# Time (in milliseconds) of the endpoints refresh interval.
proxy-refresh-interval: 30000

# Time (in milliseconds) for a dial to timeout.
proxy-dial-timeout: 1000

# Time (in milliseconds) for a write to timeout.
proxy-write-timeout: 5000

# Time (in milliseconds) for a read to timeout.
proxy-read-timeout: 0

client-transport-security:
  # Path to the client server TLS cert file.
  cert-file:

  # Path to the client server TLS key file.
  key-file:

  # Enable client cert authentication.
  client-cert-auth: false

  # Path to the client server TLS trusted CA cert file.
  trusted-ca-file:

  # Client TLS using generated certificates
  auto-tls: false

peer-transport-security:
  # Path to the peer server TLS cert file.
  cert-file:

  # Path to the peer server TLS key file.
  key-file:

  # Enable peer client cert authentication.
  client-cert-auth: false

  # Path to the peer server TLS trusted CA cert file.
  trusted-ca-file:

  # Peer TLS using generated certificates.
  auto-tls: false

# Enable debug-level logging for etcd.
log-level: debug

logger: zap

# Specify 'stdout' or 'stderr' to skip journald logging even when running under systemd.
log-outputs: [stderr]

# Force to create a new one member cluster.
force-new-cluster: false

auto-compaction-mode: periodic
auto-compaction-retention: "1"

Etcd2 的配置文件

# This is the configuration file for the etcd server.

# Human-readable name for this member.
name: 'etcd2'

# Path to the data directory.
data-dir: /var/lib/etcd

# Path to the dedicated wal directory.
wal-dir:

# Number of committed transactions to trigger a snapshot to disk.
snapshot-count: 10000

# Time (in milliseconds) of a heartbeat interval.
heartbeat-interval: 100

# Time (in milliseconds) for an election to timeout.
election-timeout: 1000

# Raise alarms when backend size exceeds the given quota. 0 means use the
# default quota.
quota-backend-bytes: 0

# List of comma separated URLs to listen on for peer traffic.
listen-peer-urls: http://172.17.0.3:2380

# List of comma separated URLs to listen on for client traffic.
listen-client-urls: http://172.17.0.3:2379,http://localhost:2379

# Maximum number of snapshot files to retain (0 is unlimited).
max-snapshots: 5

# Maximum number of wal files to retain (0 is unlimited).
max-wals: 5

# Comma-separated white list of origins for CORS (cross-origin resource sharing).
cors:

# List of this member's peer URLs to advertise to the rest of the cluster.
# The URLs needed to be a comma-separated list.
initial-advertise-peer-urls: http://172.17.0.3:2380

# List of this member's client URLs to advertise to the public.
# The URLs needed to be a comma-separated list.
advertise-client-urls: http://172.17.0.3:2379

# Discovery URL used to bootstrap the cluster.
discovery:

# Valid values include 'exit', 'proxy'
discovery-fallback: 'proxy'

# HTTP proxy to use for traffic to discovery service.
discovery-proxy:

# DNS domain used to bootstrap initial cluster.
discovery-srv:

# Initial cluster configuration for bootstrapping.
initial-cluster: etcd1=http://172.17.0.2:2380,etcd2=http://172.17.0.3:2380,etcd3=http://172.17.0.4:2380

# Initial cluster token for the etcd cluster during bootstrap.
initial-cluster-token: 'etcd-cluster1'

# Initial cluster state ('new' or 'existing').
initial-cluster-state: 'new'

# Reject reconfiguration requests that would cause quorum loss.
strict-reconfig-check: false

# Accept etcd V2 client requests
enable-v2: true

# Enable runtime profiling data via HTTP server
enable-pprof: true

# Valid values include 'on', 'readonly', 'off'
proxy: 'off'

# Time (in milliseconds) an endpoint will be held in a failed state.
proxy-failure-wait: 5000

# Time (in milliseconds) of the endpoints refresh interval.
proxy-refresh-interval: 30000

# Time (in milliseconds) for a dial to timeout.
proxy-dial-timeout: 1000

# Time (in milliseconds) for a write to timeout.
proxy-write-timeout: 5000

# Time (in milliseconds) for a read to timeout.
proxy-read-timeout: 0

client-transport-security:
  # Path to the client server TLS cert file.
  cert-file:

  # Path to the client server TLS key file.
  key-file:

  # Enable client cert authentication.
  client-cert-auth: false

  # Path to the client server TLS trusted CA cert file.
  trusted-ca-file:

  # Client TLS using generated certificates
  auto-tls: false

peer-transport-security:
  # Path to the peer server TLS cert file.
  cert-file:

  # Path to the peer server TLS key file.
  key-file:

  # Enable peer client cert authentication.
  client-cert-auth: false

  # Path to the peer server TLS trusted CA cert file.
  trusted-ca-file:

  # Peer TLS using generated certificates.
  auto-tls: false

# Enable debug-level logging for etcd.
log-level: debug

logger: zap

# Specify 'stdout' or 'stderr' to skip journald logging even when running under systemd.
log-outputs: [stderr]

# Force to create a new one member cluster.
force-new-cluster: false

auto-compaction-mode: periodic
auto-compaction-retention: "1"

Etcd3 的配置文件

# This is the configuration file for the etcd server.

# Human-readable name for this member.
name: 'etcd3'

# Path to the data directory.
data-dir: /var/lib/etcd

# Path to the dedicated wal directory.
wal-dir:

# Number of committed transactions to trigger a snapshot to disk.
snapshot-count: 10000

# Time (in milliseconds) of a heartbeat interval.
heartbeat-interval: 100

# Time (in milliseconds) for an election to timeout.
election-timeout: 1000

# Raise alarms when backend size exceeds the given quota. 0 means use the
# default quota.
quota-backend-bytes: 0

# List of comma separated URLs to listen on for peer traffic.
listen-peer-urls: http://172.17.0.4:2380

# List of comma separated URLs to listen on for client traffic.
listen-client-urls: http://172.17.0.4:2379,http://localhost:2379

# Maximum number of snapshot files to retain (0 is unlimited).
max-snapshots: 5

# Maximum number of wal files to retain (0 is unlimited).
max-wals: 5

# Comma-separated white list of origins for CORS (cross-origin resource sharing).
cors:

# List of this member's peer URLs to advertise to the rest of the cluster.
# The URLs needed to be a comma-separated list.
initial-advertise-peer-urls: http://172.17.0.4:2380

# List of this member's client URLs to advertise to the public.
# The URLs needed to be a comma-separated list.
advertise-client-urls: http://172.17.0.4:2379

# Discovery URL used to bootstrap the cluster.
discovery:

# Valid values include 'exit', 'proxy'
discovery-fallback: 'proxy'

# HTTP proxy to use for traffic to discovery service.
discovery-proxy:

# DNS domain used to bootstrap initial cluster.
discovery-srv:

# Initial cluster configuration for bootstrapping.
initial-cluster: etcd1=http://172.17.0.2:2380,etcd2=http://172.17.0.3:2380,etcd3=http://172.17.0.4:2380

# Initial cluster token for the etcd cluster during bootstrap.
initial-cluster-token: 'etcd-cluster1'

# Initial cluster state ('new' or 'existing').
initial-cluster-state: 'new'

# Reject reconfiguration requests that would cause quorum loss.
strict-reconfig-check: false

# Accept etcd V2 client requests
enable-v2: true

# Enable runtime profiling data via HTTP server
enable-pprof: true

# Valid values include 'on', 'readonly', 'off'
proxy: 'off'

# Time (in milliseconds) an endpoint will be held in a failed state.
proxy-failure-wait: 5000

# Time (in milliseconds) of the endpoints refresh interval.
proxy-refresh-interval: 30000

# Time (in milliseconds) for a dial to timeout.
proxy-dial-timeout: 1000

# Time (in milliseconds) for a write to timeout.
proxy-write-timeout: 5000

# Time (in milliseconds) for a read to timeout.
proxy-read-timeout: 0

client-transport-security:
  # Path to the client server TLS cert file.
  cert-file:

  # Path to the client server TLS key file.
  key-file:

  # Enable client cert authentication.
  client-cert-auth: false

  # Path to the client server TLS trusted CA cert file.
  trusted-ca-file:

  # Client TLS using generated certificates
  auto-tls: false

peer-transport-security:
  # Path to the peer server TLS cert file.
  cert-file:

  # Path to the peer server TLS key file.
  key-file:

  # Enable peer client cert authentication.
  client-cert-auth: false

  # Path to the peer server TLS trusted CA cert file.
  trusted-ca-file:

  # Peer TLS using generated certificates.
  auto-tls: false

# Enable debug-level logging for etcd.
log-level: debug

logger: zap

# Specify 'stdout' or 'stderr' to skip journald logging even when running under systemd.
log-outputs: [stderr]

# Force to create a new one member cluster.
force-new-cluster: false

auto-compaction-mode: periodic
auto-compaction-retention: "1"

使用配置文件运行各节点组成集群

在各个容器中分别执行：

bin/etcd --config-file etcd.conf.yml

集群应该已经正常运行了。

等等 ， 仔细看日志

好吧 ，启动失败,看这个它是说 找不到etcd1仔细看，这时候就要看你的配置文件了，果然找到了

# 修改前
initial-cluster: infra1=http://172.17.0.2:2380,infra2=http://172.17.0.3:2380,infra3=http://172.17.0.4:2380

# 修改后
initial-cluster: etcd1=http://172.17.0.2:2380,etcd2=http://172.17.0.3:2380,etcd3=http://172.17.0.4:2380

使用 etcdctl 连接到 etcd

这时候我们再打开一个终端查看

# 方式一
# 设置环境变量
export ETCDCTL_API=3
HOST_1=172.17.0.2
HOST_2=172.17.0.3
HOST_3=172.17.0.4
ENDPOINTS=$HOST_1:2379,$HOST_2:2379,$HOST_3:2379

# 方式二
# 连接
./etcdctl --endpoints=$ENDPOINTS member list

./etcdctl --endpoints=http://172.17.0.2:2379,http://172.17.0.3:2379,http://172.17.0.4:2379  endpoint status -w table

能查看状态说明我们的集群已经设置成功了

使用go 操作Etcd

其实上面我已经已经可以使用 etcdctl客户端操作 etcd集群了，但是我们在实际使用中不可能使用这个去操作，一般都是在 go里面写代码操作

官方提供的库和工具

https://etcd.io/docs/v3.5/integrations/

这里我们使用GO的 etcd/clientv3进行操作

GitHub: https://github.com/etcd-io/etcd/tree/main/client/v3

官方使用文档：https://pkg.go.dev/go.etcd.io/etcd/client/v3#section-readme

go etcd hello world

学啥东西都是从 hello world 开始,这里我们向etcd 集群写入一个 hello world 并取出输出

首先我们肯定是要创建项目了，创建一个 etcd_test的文件夹

# 初始化项目
go mod init etcd_test

# 安装/etcd/client/v3 包
go get go.etcd.io/etcd/client/v3

创建main.go ，并写入下面的内容

package main

import (
	"context"
	"fmt"
	"time"

	clientv3 "go.etcd.io/etcd/client/v3"
)

func main() {
	cli, err := clientv3.New(clientv3.Config{
    // 注意：容器是暴露到本季的端口中
		Endpoints:   []string{"127.0.0.1:22379"},
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		fmt.Printf("连接失败，错误信息：%+v", err)
	}
	defer cli.Close()
	// put
	// 设置超时时间
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	_, err = cli.Put(ctx, "test", "hello world")
	cancel()
	if err != nil {
		fmt.Printf("put 操作失败, err:%v\n", err)
		return
	}
	// get
	ctx, cancel = context.WithTimeout(context.Background(), time.Second)
	resp, err := cli.Get(ctx, "test")
	cancel()
	if err != nil {
		fmt.Printf("get 操作失败, err:%v\n", err)
		return
	}
	for _, ev := range resp.Kvs {
		fmt.Printf("%s:%s\n", ev.Key, ev.Value)
	}
}

put, get, delete, watch 方法

其实上面的 hello world 案例我们已经 使用到了 put, get 方法，没错，这几个方式就是顾名思义

• put：修改或删除
• get：获取
• delete：删除
• wathc：监听

下面来个综合案例：

监听 key 为 test2 的 值变化情况

案例

文件：main.go

package main

import (
	"context"
	"fmt"
	"time"

	clientv3 "go.etcd.io/etcd/client/v3"
)

func main() {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   []string{"127.0.0.1:22379"},
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		fmt.Printf("连接失败，错误信息：%+v", err)
	}
	defer cli.Close()
	// 监听 test2
	// 派一个哨兵 一直监视 key 的变化（新增，修改，删除)
	ch := cli.Watch(context.Background(), "test2")
	// 尝试重通道取值（监视信息）
	for wresp := range ch {
		for _, evt := range wresp.Events {
			fmt.Printf("type:%v; key:%v; value:%v \n", evt.Type, string(evt.Kv.Key), string(evt.Kv.Value))
		}
	}

}

文件：main2.go

package main

import (
	"context"
	"fmt"
	"time"

	clientv3 "go.etcd.io/etcd/client/v3"
)

func main() {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   []string{"127.0.0.1:22379"},
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		fmt.Printf("连接失败，错误信息：%+v", err)
	}
	defer cli.Close()

	// 创建客户端这个回话存活 2 s
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)

	// put 新增
	_, err = cli.Put(ctx, "test2", "新增")
	cancel()
	if err != nil {
		fmt.Printf("put 操作失败, err:%v\n", err)
		return
	}

	ctx, cancel = context.WithTimeout(context.Background(), time.Second)
	// put 修改
	_, err = cli.Put(ctx, "test2", "修改")
	cancel()
	if err != nil {
		fmt.Printf("put 操作失败, err:%v\n", err)
		return
	}

	ctx, cancel = context.WithTimeout(context.Background(), time.Second)
	// get 获取
	resp, err := cli.Get(ctx, "test2")
	cancel()
	if err != nil {
		fmt.Printf("get 操作失败, err:%v\n", err)
		return
	}
	for _, ev := range resp.Kvs {
		fmt.Printf("%s:%s\n", ev.Key, ev.Value)
	}

	ctx, cancel = context.WithTimeout(context.Background(), time.Second)
	// 删除
	_, err = cli.Delete(ctx, "test2")
	cancel()
	if err != nil {
		panic(err.Error())
	}
}

分别执行

go run main.go
go run main2.go

结果

可以看到已经监听到了 新增，修改，删除

etcd实现服务注册和发现

方法汇总

• clientv3.New: 创建etcdv3客户端(func New(cfg Config) (*Client, error))
• clientv3.Config: 创建客户端时使用的配置
• Grant: 初始化一个新租约(Grant(ctx context.Context, ttl int64) (*LeaseGrantResponse, error))
• Put: 注册服务并绑定租约
• KeepAlive: 设置续租,定期发送续租请求 (KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error))
• Revoke: 撤销租约
• Get: 获取服务
• Watch: 监控服务

实现流程

服务注册实现案例

package main

import (
	"context"
	"log"
	"time"

	clientv3 "go.etcd.io/etcd/client/v3"
)

// ServiceRegister 创建租约注册服务
type ServiceRegister struct {
	cli     *clientv3.Client //etcd client
	leaseID clientv3.LeaseID //租约ID
	//租约keepalieve相应chan
	keepAliveChan <-chan *clientv3.LeaseKeepAliveResponse
	key           string //key
	val           string //value
}

// NewServiceRegister 新建注册服务
func NewServiceRegister(endpoints []string, key, val string, lease int64) (*ServiceRegister, error) {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   endpoints,
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		log.Fatal(err)
	}

	ser := &ServiceRegister{
		cli: cli,
		key: key,
		val: val,
	}
	//申请租约设置时间keepalive并注册服务
	if err := ser.putKeyWithLease(lease); err != nil {
		return nil, err
	}

	return ser, nil
}

// 设置租约
func (s *ServiceRegister) putKeyWithLease(lease int64) error {
	//设置租约时间
	resp, err := s.cli.Grant(context.Background(), lease)
	if err != nil {
		return err
	}
	//注册服务并绑定租约
	_, err = s.cli.Put(context.Background(), s.key, s.val, clientv3.WithLease(resp.ID))
	if err != nil {
		return err
	}
	//设置续租 定期发送需求请求
	leaseRespChan, err := s.cli.KeepAlive(context.Background(), resp.ID)

	if err != nil {
		return err
	}
	s.leaseID = resp.ID
	log.Println(s.leaseID)
	s.keepAliveChan = leaseRespChan
	log.Printf("Put key:%s  val:%s  success!", s.key, s.val)
	return nil
}

// ListenLeaseRespChan 监听 续租情况
func (s *ServiceRegister) ListenLeaseRespChan() {
	for leaseKeepResp := range s.keepAliveChan {
		log.Println("续约成功", leaseKeepResp)
	}
	log.Println("关闭续租")
}

// Close 注销服务
func (s *ServiceRegister) Close() error {
	//撤销租约
	if _, err := s.cli.Revoke(context.Background(), s.leaseID); err != nil {
		return err
	}
	log.Println("撤销租约")
	return s.cli.Close()
}

func main() {
	// 集群节点
	var endpoints = []string{"127.0.0.1.:22379"}
	ser, err := NewServiceRegister(endpoints, "/web", "172.17.0.3:2379", 5)
	if err != nil {
		log.Fatalln(err)
	}
	//监听续租相应chan
	go ser.ListenLeaseRespChan()
	select {
	// 30 秒后关闭租约
	case <-time.After(30 * time.Second):
		ser.Close()
	}
}

服务发现实现案例

package main

import (
	"context"
	"log"
	"sync"
	"time"

	mvccpb "go.etcd.io/etcd/api/v3/mvccpb"
	clientv3 "go.etcd.io/etcd/client/v3"
)

// ServiceDiscovery 服务发现
type ServiceDiscovery struct {
	cli        *clientv3.Client  //etcd client
	serverList map[string]string //服务列表
	lock       sync.Mutex
}

// NewServiceDiscovery  新建发现服务
func NewServiceDiscovery(endpoints []string) *ServiceDiscovery {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   endpoints,
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		log.Fatal(err)
	}

	return &ServiceDiscovery{
		cli:        cli,
		serverList: make(map[string]string),
	}
}

// WatchService 初始化服务列表和监视
func (s *ServiceDiscovery) WatchService(prefix string) error {
	//根据前缀获取现有的key
	resp, err := s.cli.Get(context.Background(), prefix, clientv3.WithPrefix())
	if err != nil {
		return err
	}

	for _, ev := range resp.Kvs {
		s.SetServiceList(string(ev.Key), string(ev.Value))
	}

	//监视前缀，修改变更的server
	go s.watcher(prefix)
	return nil
}

// watcher 监听前缀
func (s *ServiceDiscovery) watcher(prefix string) {
	rch := s.cli.Watch(context.Background(), prefix, clientv3.WithPrefix())
	log.Printf("watching prefix:%s now...", prefix)
	for wresp := range rch {
		for _, ev := range wresp.Events {
			switch ev.Type {
			case mvccpb.PUT: //修改或者新增
				s.SetServiceList(string(ev.Kv.Key), string(ev.Kv.Value))
			case mvccpb.DELETE: //删除
				s.DelServiceList(string(ev.Kv.Key))
			}
		}
	}
}

// SetServiceList 新增服务地址
func (s *ServiceDiscovery) SetServiceList(key, val string) {
	s.lock.Lock()
	defer s.lock.Unlock()
	s.serverList[key] = string(val)
	log.Println("put key :", key, "val:", val)
}

// DelServiceList 删除服务地址
func (s *ServiceDiscovery) DelServiceList(key string) {
	s.lock.Lock()
	defer s.lock.Unlock()
	delete(s.serverList, key)
	log.Println("del key:", key)
}

// GetServices 获取服务地址
func (s *ServiceDiscovery) GetServices() []string {
	s.lock.Lock()
	defer s.lock.Unlock()
	addrs := make([]string, 0)

	for _, v := range s.serverList {
		addrs = append(addrs, v)
	}
	return addrs
}

// Close 关闭服务
func (s *ServiceDiscovery) Close() error {
	return s.cli.Close()
}

func main() {
	var endpoints = []string{"127.0.0.1:22379"}
	ser := NewServiceDiscovery(endpoints)
	defer ser.Close()
	_ = ser.WatchService("/web")
	for {
		select {
		case <-time.Tick(10 * time.Second):
			log.Println(ser.GetServices())
		}
	}
}

案例结果