Go 使用 consul 做服務發現
前言
前面一章講了微服務的一些優點和缺點，那如何做到
一、目標
二、使用步驟
1. 安裝 consul
我們可以直接使用官方提供的二進位制檔案來進行安裝部署，其官網地址為 https://www.consul.io/downloads
下載後為可執行檔案，在我們開發試驗過程中，可以直接使用 consul agent -dev 命令來啟動一個單節點的 consul
在啟動的列印日誌中可以看到 agent: Started HTTP server on 127.0.0.1:8500 (tcp), 我們可以在瀏覽器直接訪問 127.0.0.1:8500 即可看到如下
這裡我們的 consul 就啟動成功了
2. 服務註冊
在網路程式設計中，一般會提供專案的 IP、PORT、PROTOCOL，在服務治理中，我們還需要知道對應的服務名、例項名以及一些自定義的擴充套件資訊
在這裡使用 ServiceInstance 介面來規定註冊服務時必須的一些資訊，同時用 DefaultServiceInstance 實現
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) {
// 如果沒有傳入 IP 則獲取一下，這個方法在多網路卡的情況下，並不好用
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
}
定義介面
在上面規定了需要註冊的服務的必要資訊，下面定義下服務註冊和剔除的方法
type ServiceRegistry interface {
Register(serviceInstance cloud.ServiceInstance) bool
Deregister()
}
具體實現
因為 consul 提供了 http 介面來對consul 進行操作，我們也可以使用 http 請求方式進行註冊和剔除操作，具體 http 介面文件見 https://www.consul.io/api-docs, consul 預設提供了go 語言的實現，這裡直接使用 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 {
// 建立註冊到consul的服務到
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健康檢查回撥函式
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" // 故障檢查失敗30s後 consul自動將註冊服務刪除
registration.Check = check
// 註冊服務到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
}
測試用例
註冊服務的程式碼基本完成，來測試一下
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()
// 健康檢測介面，其實只要是 200 就認為成功了
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，則會在 consul 看到 go-user-server 這個服務
3. 服務發現
在服務發現中，一般會需要兩個方法
- 獲取所有的服務列表
- 獲取指定的服務的所有例項資訊
介面定義
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)
}
具體實現
來實現一下
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
}
測試用例
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"))
}
結果
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>
總結
通過使用 consul api 我們可以簡單的實現基於 consul 的服務發現，在通過結合 http rpc 就可簡單的實現服務的呼叫，下面一章來簡單講下 go 如何發起 http 請求，為我們做 rpc 做個鋪墊
參考
