系列文章目录

微服务 | Spring Cloud(一)：从单体SSM 到 Spring Cloud
Go | Gin 解决跨域问题跨域配置

前言

前面一章讲了微服务的一些优点和缺点，那如何做到服务动态发现呢？

一、目标

二、使用步骤

1. 安装 consul

我们可以直接使用官方提供的二进制文件来进行安装部署，其官网地址为 www.consul.io/downloads 在这里插入图片描述下载后为可执行文件，在我们开发试验过程中，可以直接使用 consul agent -dev 命令来启动一个单节点的 consul

在启动的打印日志中可以看到 agent: Started HTTP server on 127.0.0.1:8500 (tcp), 我们可以在浏览器直接访问 127.0.0.1:8500 即可看到如下在这里插入图片描述这里我们的 consul 就启动成功了

2. 服务注册

在网络编程中，一般会提供项目的 IP、PORT、PROTOCOL，在服务治理中，我们还需要知道对应的服务名、实例名以及一些自定义的扩展信息

在这里使用 ServiceInstance 接口来规定注册服务时必须的一些信息，同时用 DefaultServiceInstance 实现

type ServiceInstance interface {

	// return The unique instance ID as registered.
	GetInstanceId() string

	// return The service ID as registered.
	GetServiceId() string

	// return The hostname of the registered service instance.
	GetHost() string

	// return The port of the registered service instance.
	GetPort() int

	// return Whether the port of the registered service instance uses HTTPS.
	IsSecure() bool

	// return The key / value pair metadata associated with the service instance.
	GetMetadata() map[string]string
}

type DefaultServiceInstance struct {
	InstanceId string
	ServiceId  string
	Host       string
	Port       int
	Secure     bool
	Metadata   map[string]string
}

func NewDefaultServiceInstance(serviceId string, host string, port int, secure bool,
	metadata map[string]string, instanceId string) (*DefaultServiceInstance, error) {

	// 如果没有传入 IP 则获取一下，这个方法在多网卡的情况下，并不好用
	if len(host) == 0 {
		localIP, err := util.GetLocalIP()
		if err != nil {
			return nil, err
		}
		host = localIP
	}

	if len(instanceId) == 0 {
		instanceId = serviceId + "-" + strconv.FormatInt(time.Now().Unix(), 10) + "-" + strconv.Itoa(rand.Intn(9000)+1000)
	}

	return &DefaultServiceInstance{InstanceId: instanceId, ServiceId: serviceId, Host: host, Port: port, Secure: secure, Metadata: metadata}, nil
}

func (serviceInstance DefaultServiceInstance) GetInstanceId() string {
	return serviceInstance.InstanceId
}

func (serviceInstance DefaultServiceInstance) GetServiceId() string {
	return serviceInstance.ServiceId
}

func (serviceInstance DefaultServiceInstance) GetHost() string {
	return serviceInstance.Host
}

func (serviceInstance DefaultServiceInstance) GetPort() int {
	return serviceInstance.Port
}

func (serviceInstance DefaultServiceInstance) IsSecure() bool {
	return serviceInstance.Secure
}

func (serviceInstance DefaultServiceInstance) GetMetadata() map[string]string {
	return serviceInstance.Metadata
}

定义接口

在上面规定了需要注册的服务的必要信息，下面定义下服务注册和剔除的方法

type ServiceRegistry interface {
	Register(serviceInstance cloud.ServiceInstance) bool

	Deregister()
}

具体实现

因为 consul 提供了 http 接口来对consul 进行操作，我们也可以使用 http 请求方式进行注册和剔除操作，具体 http 接口文档见 https://www.consul.io/api-docs, consul 默认提供了go 语言的实现，这里直接使用 github.com/hashicorp/consul/api

import (
	"errors"
	"fmt"
	"github.com/hashicorp/consul/api"
	"strconv"
	"unsafe"
)

type consulServiceRegistry struct {
	serviceInstances     map[string]map[string]cloud.ServiceInstance
	client               api.Client
	localServiceInstance cloud.ServiceInstance
}

func (c consulServiceRegistry) Register(serviceInstance cloud.ServiceInstance) bool {
	// 创建注册到consul的服务到
	registration := new(api.AgentServiceRegistration)
	registration.ID = serviceInstance.GetInstanceId()
	registration.Name = serviceInstance.GetServiceId()
	registration.Port = serviceInstance.GetPort()
	var tags []string
	if serviceInstance.IsSecure() {
		tags = append(tags, "secure=true")
	} else {
		tags = append(tags, "secure=false")
	}
	if serviceInstance.GetMetadata() != nil {
		var tags []string
		for key, value := range serviceInstance.GetMetadata() {
			tags = append(tags, key+"="+value)
		}
		registration.Tags = tags
	}
	registration.Tags = tags

	registration.Address = serviceInstance.GetHost()

	// 增加consul健康检查回调函数
	check := new(api.AgentServiceCheck)

	schema := "http"
	if serviceInstance.IsSecure() {
		schema = "https"
	}
	check.HTTP = fmt.Sprintf("%s://%s:%d/actuator/health", schema, registration.Address, registration.Port)
	check.Timeout = "5s"
	check.Interval = "5s"
	check.DeregisterCriticalServiceAfter = "20s" // 故障检查失败30s后 consul自动将注册服务删除
	registration.Check = check

	// 注册服务到consul
	err := c.client.Agent().ServiceRegister(registration)
	if err != nil {
		fmt.Println(err)
		return false
	}

	if c.serviceInstances == nil {
		c.serviceInstances = map[string]map[string]cloud.ServiceInstance{}
	}

	services := c.serviceInstances[serviceInstance.GetServiceId()]

	if services == nil {
		services = map[string]cloud.ServiceInstance{}
	}

	services[serviceInstance.GetInstanceId()] = serviceInstance

	c.serviceInstances[serviceInstance.GetServiceId()] = services

	c.localServiceInstance = serviceInstance

	return true
}

// deregister a service
func (c consulServiceRegistry) Deregister() {
	if c.serviceInstances == nil {
		return
	}

	services := c.serviceInstances[c.localServiceInstance.GetServiceId()]

	if services == nil {
		return
	}

	delete(services, c.localServiceInstance.GetInstanceId())

	if len(services) == 0 {
		delete(c.serviceInstances, c.localServiceInstance.GetServiceId())
	}

	_ = c.client.Agent().ServiceDeregister(c.localServiceInstance.GetInstanceId())

	c.localServiceInstance = nil
}

// new a consulServiceRegistry instance
// token is optional
func NewConsulServiceRegistry(host string, port int, token string) (*consulServiceRegistry, error) {
	if len(host) < 3 {
		return nil, errors.New("check host")
	}

	if port <= 0 || port > 65535 {
		return nil, errors.New("check port, port should between 1 and 65535")
	}

	config := api.DefaultConfig()
	config.Address = host + ":" + strconv.Itoa(port)
	config.Token = token
	client, err := api.NewClient(config)
	if err != nil {
		return nil, err
	}

	return &consulServiceRegistry{client: *client}, nil
}

测试用例

注册服务的代码基本完成，来测试一下

func TestConsulServiceRegistry(t *testing.T) {
	host := "127.0.0.1"
	port := 8500
	registryDiscoveryClient, _ := extension.NewConsulServiceRegistry(host, port, "")

	ip, err := util.GetLocalIP()
	if err != nil {
		t.Error(err)
	}
	
	serviceInstanceInfo, _ := cloud.NewDefaultServiceInstance("go-user-server", "", 8090,
		false, map[string]string{"user":"zyn"}, "")

	registryDiscoveryClient.Register(serviceInstanceInfo)

	r := gin.Default()
	// 健康检测接口，其实只要是 200 就认为成功了
	r.GET("/actuator/health", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"message": "pong",
		})
	})
	err = r.Run(":8090")
	if err != nil{
		registryDiscoveryClient.Deregister()
	}
}

如果成功，则会在 consul 看到 go-user-server 这个服务

3. 服务发现

在服务发现中，一般会需要两个方法

获取所有的服务列表
获取指定的服务的所有实例信息

接口定义

type DiscoveryClient interface {
	
	/**
	 * Gets all ServiceInstances associated with a particular serviceId.
	 * @param serviceId The serviceId to query.
	 * @return A List of ServiceInstance.
	 */
	GetInstances(serviceId string) ([]cloud.ServiceInstance, error)

	/**
	 * @return All known service IDs.
	 */
	GetServices() ([]string, error)
}

具体实现

来实现一下

type consulServiceRegistry struct {
	serviceInstances     map[string]map[string]cloud.ServiceInstance
	client               api.Client
	localServiceInstance cloud.ServiceInstance
}

func (c consulServiceRegistry) GetInstances(serviceId string) ([]cloud.ServiceInstance, error) {
	catalogService, _, _ := c.client.Catalog().Service(serviceId, "", nil)
	if len(catalogService) > 0 {
		result := make([]cloud.ServiceInstance, len(catalogService))
		for index, sever := range catalogService {
			s := cloud.DefaultServiceInstance{
				InstanceId: sever.ServiceID,
				ServiceId:  sever.ServiceName,
				Host:       sever.Address,
				Port:       sever.ServicePort,
				Metadata:   sever.ServiceMeta,
			}
			result[index] = s
		}
		return result, nil
	}
	return nil, nil
}

func (c consulServiceRegistry) GetServices() ([]string, error) {
	services, _, _ := c.client.Catalog().Services(nil)
	result := make([]string, unsafe.Sizeof(services))
	index := 0
	for serviceName, _ := range services {
		result[index] = serviceName
		index++
	}
	return result, nil
}

// new a consulServiceRegistry instance
// token is optional
func NewConsulServiceRegistry(host string, port int, token string) (*consulServiceRegistry, error) {
	if len(host) < 3 {
		return nil, errors.New("check host")
	}

	if port <= 0 || port > 65535 {
		return nil, errors.New("check port, port should between 1 and 65535")
	}

	config := api.DefaultConfig()
	config.Address = host + ":" + strconv.Itoa(port)
	config.Token = token
	client, err := api.NewClient(config)
	if err != nil {
		return nil, err
	}

	return &consulServiceRegistry{client: *client}, nil
}

测试用例

func TestConsulServiceDiscovery(t *testing.T) {
	host := "127.0.0.1"
	port := 8500
	token := ""
	registryDiscoveryClient, err := extension.NewConsulServiceRegistry(host, port, token)
	if err != nil {
		panic(err)
	}

	t.Log(registryDiscoveryClient.GetServices())

	t.Log(registryDiscoveryClient.GetInstances("go-user-server"))
}

结果

consul_service_registry_test.go:57: [consul go-user-server      ] <nil>

consul_service_registry_test.go:59: [{go-user-server-1602590661-56179 go-user-server 127.0.0.1 8090 false map[user:zyn]}] <nil>

总结

通过使用 consul api 我们可以简单的实现基于 consul 的服务发现，在通过结合 http rpc 就可简单的实现服务的调用，下面一章来简单讲下 go 如何发起 http 请求，为我们做 rpc 做个铺垫

具体代码见 github.com/zhangyunan1…

Go | Go 使用 consul 做服务发现

系列文章目录

前言

一、目标

二、使用步骤

1. 安装 consul

2. 服务注册

定义接口

具体实现

测试用例

3. 服务发现

接口定义

具体实现

测试用例

总结

参考