From 85229f534232697124b3afd1505aeb1495c3b4ed Mon Sep 17 00:00:00 2001
From: han-joker <hanJoker@mail.com>
Date: Fri, 14 Apr 2023 21:25:56 +0800
Subject: [PATCH] service discovery

---
 discovery/discovery.go     | 62 ++++++++++++++++++++++++++++++++++++++
 discovery/register.go      | 30 +++++++++++++++---
 discovery/services.go      | 38 +++++++++++++++++++++--
 discovery/services_test.go | 10 ++++--
 4 files changed, 130 insertions(+), 10 deletions(-)
 create mode 100644 discovery/discovery.go

diff --git a/discovery/discovery.go b/discovery/discovery.go
new file mode 100644
index 0000000..35bf02d
--- /dev/null
+++ b/discovery/discovery.go
@@ -0,0 +1,62 @@
+package discovery
+
+import (
+	"context"
+	"errors"
+	clientv3 "go.etcd.io/etcd/client/v3"
+	"math/rand"
+	"time"
+)
+
+type Discovery interface {
+	// 获取某个服务器的一个实例地址
+	GetServiceAddr(serviceName string) (string, error)
+	// 监控某个服务的地址变化
+	WatchService(serviceName string) error
+}
+
+type DiscoveryEtcd struct {
+	cli *clientv3.Client
+}
+
+// 实例化的方法
+func NewDiscoveryEtcd(endpoints []string) (*DiscoveryEtcd, error) {
+	// 一，没有etcd的地址，直接返回
+	if len(endpoints) == 0 {
+		return nil, errors.New("endpoints is empty")
+	}
+
+	// 二，连接etcd
+	cli, err := clientv3.New(clientv3.Config{
+		Endpoints:   endpoints,
+		DialTimeout: 3 * time.Second,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// 实例化
+	de := &DiscoveryEtcd{cli: cli}
+
+	return de, nil
+}
+
+func (de *DiscoveryEtcd) GetServiceAddr(serviceName string) (string, error) {
+	// 执行 Get 操作
+	getResp, err := de.cli.Get(context.Background(), serviceName, clientv3.WithPrefix())
+	if err != nil {
+		return "", err
+	}
+
+	// 处理查询到的结果
+	if len(getResp.Kvs) == 0 {
+		return "", errors.New("service not found")
+	}
+
+	// 采用随机的LB，LoadBalance 算法
+	randIndex := rand.Intn(len(getResp.Kvs)) // [0, n)
+	addr := string(getResp.Kvs[randIndex].Value)
+
+	// 返回地址
+	return addr, nil
+}
diff --git a/discovery/register.go b/discovery/register.go
index b064d2d..00689ee 100644
--- a/discovery/register.go
+++ b/discovery/register.go
@@ -15,7 +15,7 @@ type Registrar interface {
 	Register(service Service) error
 
 	// 注销服务
-	DeRegister(service Service) error
+	DeRegister() error
 }
 
 // 基于Etcd的服务发现中间件，实现Registrar
@@ -25,6 +25,8 @@ type RegistrarEtcd struct {
 	// 租约信息，基于租约来做健康监测
 	leaseID  clientv3.LeaseID
 	leaseTTL int64
+	// 续约响应channel
+	leaseKeepAliveRespCh <-chan *clientv3.LeaseKeepAliveResponse
 }
 
 const leaseTTL = 5
@@ -75,17 +77,35 @@ func (re *RegistrarEtcd) Register(service Service) error {
 	}
 
 	//三，租约续约
-	_, err = re.cli.KeepAlive(context.Background(), re.leaseID)
+	re.leaseKeepAliveRespCh, err = re.cli.KeepAlive(context.Background(), re.leaseID)
 	if err != nil {
 		return err
 	}
-
+	// 并发的接收续约的响应
+	go re.HandleKeepAliveResp()
 	// log
 	log.Printf("service %s(%s) was registed \n", service.Name(), service.Addr())
-
 	return nil
 }
+func (re *RegistrarEtcd) HandleKeepAliveResp() {
+	// 从ch中接收内容即可
+	for resp := range re.leaseKeepAliveRespCh {
+		log.Printf("service was Keepalive with %x\n", resp.ID)
+	}
+}
+
+// 注销
+// 撤销租约
+func (re *RegistrarEtcd) DeRegister() error {
+	// lease revoke
+	if _, err := re.cli.Revoke(context.Background(), re.leaseID); err != nil {
+		return err
+	}
+
+	// close etcd client
+	if err := re.cli.Close(); err != nil {
+		return err
+	}
 
-func (re *RegistrarEtcd) DeRegister(service Service) error {
 	return nil
 }
diff --git a/discovery/services.go b/discovery/services.go
index 6a343ae..02ab158 100644
--- a/discovery/services.go
+++ b/discovery/services.go
@@ -1,6 +1,10 @@
 package discovery
 
-import "log"
+import (
+	"log"
+	"os"
+	"os/signal"
+)
 
 // 服务的类型接口
 type Service interface {
@@ -42,5 +46,35 @@ func ServiceOrder(addr string) {
 
 	// 四：阻塞执行
 	log.Printf("service %s(%s) is running", orderService.Name(), orderService.Addr())
-	select {}
+	// 监控系统的终止信号，来撤销租约
+	chInt := make(chan os.Signal, 1)
+	signal.Notify(chInt, os.Interrupt) // 监控终止ctrl+c(interrupt)的信号
+	// 多路复用channel监控语句
+	select {
+	case <-chInt:
+		if err := re.DeRegister(); err != nil {
+			log.Fatalln(err)
+		}
+		log.Printf("service %s(%s) was deregisted", orderService.Name(), orderService.Addr())
+	}
+}
+
+func ServiceDriver() {
+	// 初始化服务发现中间件
+	de, err := NewDiscoveryEtcd([]string{"localhost:2379"})
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// 发现order服务
+	servcieName := "order"
+	addr, err := de.GetServiceAddr(servcieName)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	log.Printf("servie %s was discoveried on %s\n", servcieName, addr)
+
+	// 连接到目标服务，在微服务架构中，是grpc
+	// 调用（请求）目标服务的资源
 }
diff --git a/discovery/services_test.go b/discovery/services_test.go
index da7501c..f76b87f 100644
--- a/discovery/services_test.go
+++ b/discovery/services_test.go
@@ -2,12 +2,16 @@ package discovery
 
 import "testing"
 
-func TestServiceOrder1(t *testing.T) {
+func TestServiceOrder0(t *testing.T) {
 	ServiceOrder("localhost:8080")
 }
-func TestServiceOrder2(t *testing.T) {
+func TestServiceOrder1(t *testing.T) {
 	ServiceOrder("localhost:8081")
 }
-func TestServiceOrder3(t *testing.T) {
+func TestServiceOrder2(t *testing.T) {
 	ServiceOrder("localhost:8082")
 }
+
+func TestServiceDriver(t *testing.T) {
+	ServiceDriver()
+}