etcd是什么

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etcd能做什么

系统关键数据存储(配置中心)
服务注册与发现
分布式锁
发布订阅
事件监听

etcd服务发现与注册原理

创建一个对某目录(以/order-srv)的Watcher监听，通过阻塞持续租约保持对/order-srv目录的持续监听

/order-srv
├── order1
├── order2
├── order3
├── order4
└── order5

有一个新的order实例加入到被监听的目录/order-srv，此时/order-srv目录会发生addEvent，被监听器捕获

/order-srv
├── order1
├── order2
├── order3
├── order4
└── order5
└── orderNew

监听器捕获到addEvent事件后，通过raft一致性协议同主节点/order-srv目录下的数据到follower节点，通过ack成功响应数目来确定本次是不是成功
对每一个新加入目录/order-srv的实例启动一个心跳检测线程，如果心跳超时，则将该实例从/order-srv中删除，并通过raft协议在不同etcd节点间同步数据(order5)

/order-srv
├── order1
├── order2
├── order3
├── order4
└── orderNew

客户端从目录/order-srv随机获取一个order实例(负载均衡)

基于go实现etcd服务发现与注册

服务注册

package main

import (
	"context"
	"log"
	"time"

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

//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
	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() {
	var endpoints = []string{"localhost:2379"}
	ser, err := NewServiceRegister(endpoints, "/web/node1", "localhost:8000", 5)
	if err != nil {
		log.Fatalln(err)
	}
	//监听续租相应chan
	go ser.ListenLeaseRespChan()
	select {
	// case <-time.After(20 * time.Second):
	// 	ser.Close()
	}
}

服务发现

package main

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

	"github.com/coreos/etcd/mvcc/mvccpb"
	"go.etcd.io/etcd/clientv3"
)

//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{"localhost:2379"}
	ser := NewServiceDiscovery(endpoints)
	defer ser.Close()
	ser.WatchService("/web/")
	ser.WatchService("/gRPC/")
	for {
		select {
		case <-time.Tick(10 * time.Second):
			log.Println(ser.GetServices())
		}
	}
}

微服务-服务发现-etcd

etcd是什么

etcd能做什么

etcd服务发现与注册原理

基于go实现etcd服务发现与注册