Go | Go 使用 consul 做服务发现

系列文章目录

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@TOC

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前言

前面一章讲了微服务的一些优点和缺点，那如何做到

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 https://www.consul.io/downloads

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

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

1. 获取所有的服务列表
2. 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 https://github.com/zhangyunan...

参考

• https://www.consul.io/api-docs
• https://github.com/hashicorp/...