4. 参考 go 代码——服务注册与发现

来源自etcd 笔记（09）— 基于 etcd 实现微服务的注册与发现_serviceregistry": { "type": "etcd", "endpoints":-CSDN博客

服务注册

package main

import (
	"context"
	"fmt"
	"time"

	"github.com/coreos/etcd/clientv3"
)

// 服务注册对象
type ServiceRegister struct {
	client     *clientv3.Client
	kv         clientv3.KV
	lease      clientv3.Lease
	canclefunc func()
	key        string

	leaseResp     *clientv3.LeaseGrantResponse
	keepAliveChan <-chan *clientv3.LeaseKeepAliveResponse
}

// 初始化注册服务
func InitService(host []string, timeSeconds int64) (*ServiceRegister, error) {
	config := clientv3.Config{
		Endpoints:   host,
		DialTimeout: 5 * time.Second,
	}

	client, err := clientv3.New(config)
	if err != nil {
		fmt.Printf("create connection etcd failed %s\n", err)
		return nil, err
	}

	// 得到KV和Lease的API子集
	kv := clientv3.NewKV(client)
	lease := clientv3.NewLease(client)

	service := &ServiceRegister{
		client: client,
		kv:     kv,
		lease:  lease,
	}
	return service, nil
}

// 设置租约
func (s *ServiceRegister) setLease(timeSeconds int64) error {
	leaseResp, err := s.lease.Grant(context.TODO(), timeSeconds)
	if err != nil {
		fmt.Printf("create lease failed %s\n", err)
		return err
	}

	// 设置续租
	ctx, cancelFunc := context.WithCancel(context.TODO())
	leaseRespChan, err := s.lease.KeepAlive(ctx, leaseResp.ID)
	if err != nil {
		fmt.Printf("KeepAlive failed %s\n", err)
		return err
	}

	s.leaseResp = leaseResp
	s.canclefunc = cancelFunc
	s.keepAliveChan = leaseRespChan
	return nil
}

// 监听续租情况
func (s *ServiceRegister) ListenLeaseRespChan() {
	for {
		select {
		case leaseKeepResp := <-s.keepAliveChan:
			if leaseKeepResp == nil {
				fmt.Println("续租功能已经关闭")
				return
			} else {
				fmt.Println("续租成功")
			}
		}
	}
}

// 通过租约注册服务
func (s *ServiceRegister) PutService(key, val string) error {
	fmt.Printf("PutService key <%s> val <%s>\n", key, val)
	_, err := s.kv.Put(context.TODO(), key, val, clientv3.WithLease(s.leaseResp.ID))
	return err
}

// 撤销租约
func (s *ServiceRegister) RevokeLease() error {
	s.canclefunc()
	time.Sleep(2 * time.Second)
	_, err := s.lease.Revoke(context.TODO(), s.leaseResp.ID)
	return err

}

func main() {
	service, _ := InitService([]string{"127.0.0.1:12379", "127.0.0.1:22379", "127.0.0.1:32379"}, 5)
	service.setLease(10)
	defer service.RevokeLease()
	go service.ListenLeaseRespChan()

	err := service.PutService("/wohu", "http://localhost:8080")
	if err != nil {
		fmt.Printf("PutService failed %s\n", err)
	}
	// 使得程序阻塞运行，便于观察输出结果
	select {}
}

服务发现

package main

import (
	"context"
	"fmt"
	"sync"
	"time"

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

// 客户端对象
type Client struct {
	client     *clientv3.Client
	kv         clientv3.KV
	lease      clientv3.Lease
	watch      clientv3.Watcher
	serverList map[string]string
	lock       sync.Mutex
}

// 初始化客户端对象
func InitClient(addr []string) (*Client, error) {
	conf := clientv3.Config{
		Endpoints:   addr,
		DialTimeout: 5 * time.Second,
	}
	client, err := clientv3.New(conf)
	if err != nil {
		fmt.Printf("create connection etcd failed %s\n", err)
		return nil, err
	}

	// 得到 KV 、Lease、 Watcher 的API子集
	kv := clientv3.NewKV(client)
	lease := clientv3.NewLease(client)
	watch := clientv3.NewWatcher(client)

	// 给客户端对象赋值
	c := &Client{
		client:     client,
		kv:         kv,
		lease:      lease,
		watch:      watch,
		serverList: make(map[string]string),
	}
	return c, nil
}

// 根据注册的服务名，获取服务实例的信息
func (c *Client) getServiceByName(prefix string) ([]string, error) {
	// 读取的时候带有 WithPrefix 选项，所以会读取该前缀所有的字段值
	resp, err := c.kv.Get(context.Background(), prefix, clientv3.WithPrefix())
	if err != nil {
		fmt.Printf("getServiceByName failed %s\n", err)
		return nil, err
	}
	// 返回的 resp 是多个字段值。需要遍历提取对应的 key value
	addrs := c.extractAddrs(resp)
	return addrs, nil

}

// 根据 etcd 的响应，提取服务实例的数组
func (c *Client) extractAddrs(resp *clientv3.GetResponse) []string {
	addrs := make([]string, 0)
	if resp == nil || resp.Kvs == nil {
		return addrs
	}

	for i := range resp.Kvs {
		if v := resp.Kvs[i].Value; v != nil {
			// 将 key  value 值保存在  ServiceList 表中
			c.SetServiceList(string(resp.Kvs[i].Key), string(resp.Kvs[i].Value))
			addrs = append(addrs, string(v))
		}
	}
	return addrs
}

// 设置 serverList
func (c *Client) SetServiceList(key, val string) {
	c.lock.Lock()
	defer c.lock.Unlock()
	// serverList 为初始化设置的本地 map 对象，由于考虑到多个 client 运行，所以需要加锁控制
	c.serverList[key] = string(val)
	fmt.Println("set data key :", key, "val:", val)
}

// 删除本地缓存的服务实例信息
func (c *Client) DelServiceList(key string) {
	c.lock.Lock()
	defer c.lock.Unlock()
	delete(c.serverList, key)
	fmt.Println("del data key:", key)

	newRes, err := c.getServiceByName(key)
	if err != nil {
		fmt.Printf("getServiceByName failed %s\n", err)
	} else {
		fmt.Printf("get  key %s", key, " current val is: %v\n", newRes)
	}

}

// 获取服务实例信息
func (c *Client) GetService(prefix string) ([]string, error) {
	if addrs, err := c.getServiceByName(prefix); err != nil {
		panic(err)
	} else {
		fmt.Println("get service ", prefix, " for instance list: ", addrs)
		go c.watcher(prefix)
		return addrs, nil
	}
}

// 监控指定键值对的变更
func (c *Client) watcher(prefix string) {
	watchRespChan := c.watch.Watch(context.Background(), prefix, clientv3.WithPrefix())
	for watchResp := range watchRespChan {
		for _, event := range watchResp.Events {
			switch event.Type {
			case mvccpb.PUT: // 写入的事件
				c.SetServiceList(string(event.Kv.Key), string(event.Kv.Value))
			case mvccpb.DELETE: // 删除的事件
				c.DelServiceList(string(event.Kv.Key))
			}
		}
	}
}

func main() {
	/*
		先创建 etcd 连接，构建 Client 对象，随后获取指定的服务 /wohu 实例信息；
		最后监测 wohu 服务实例的变更事件，根据不同的事件产生不同的行为。
	*/

	c, _ := InitClient([]string{"127.0.0.1:12379", "127.0.0.1:22379", "127.0.0.1:32379"})
	c.GetService("/wohu")

	// 使得程序阻塞运行，模拟服务的持续运行
	select {}
}