Go | Go 使用 consul 做服务发现

迷南。 2022-12-14 03:42 151阅读 0赞

# 系列文章目录 #

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

--------------------

### 文章目录 ###

*  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

--------------------

# 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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5bmRldg_size_16_color_FFFFFF_t_70_pic_center]  
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][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5bmRldg_size_16_color_FFFFFF_t_70_pic_center 1]  
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/zhangyunan1994/lemon

# 参考 #

*  https://www.consul.io/api-docs
 *  https://github.com/hashicorp/consul/tree/master/api

[_ Spring Cloud_SSM _ Spring Cloud]: https://blog.csdn.net/zyndev/article/details/84102893
[Go _ Gin _]: https://blog.csdn.net/zyndev/article/details/108188255
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