Golang分布式注册中心实现流程讲解

2023-05-19 17:05:38 分布式流程讲解

动手实现一个分布式注册中心

以一个日志微服务为例，将日志服务注册到注册中心展开！

日志服务

log/Server.go

其实这一个日志类的功能就是有基本的写文件功能，然后就是注册一个Http的接口去写日志进去

package log
import (
	"io/ioutil"
	stlog "log"
	"net/http"
	"os"
)
var log *stlog.Logger
type fileLog string
// 编写日志的方法
func (fl fileLog) Write(data []byte) (int, error) {
	f, err := os.OpenFile(string(fl), os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
	if err != nil {
		return 0, err
	}
	defer f.Close()
	return f.Write(data)
}
// 启动一个日志对象 参数为日志文件名
func Run(destination string) {
	log = stlog.New(fileLog(destination), "[go] - ", stlog.LstdFlags)
}
// 自身注册的一个服务方法
func RegisterHandlers() {
	http.HandleFunc("/log", func(w http.ResponseWriter, r *http.Request) {
		switch r.Method {
		case http.MethodPost:
			msg, err := ioutil.ReadAll(r.Body)
			if err != nil || len(msg) == 0 {
				w.WriteHeader(http.StatusBadRequest)
				return
			}
			write(string(msg))
		default:
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
	})
}
func write(message string) {
	log.Printf("%v\n", message)
}

log/Client.go

提供给外部服务的接口，定义好日志的命名格式，来显示调用接口去使用已经注册好的日志接口并且返回状态

package log
import (
	"bytes"
	"distributed/registry"
	"fmt"
	"net/http"
	stlog "log"
)
func SetClientLogger(serviceURL string, clientService registry.ServiceName) {
	stlog.SetPrefix(fmt.Sprintf("[%v] - ", clientService))
	stlog.SetFlags(0)
	stlog.SetOutput(&clientLogger{url: serviceURL})
}
type clientLogger struct {
	url string
}
func (cl clientLogger) Write(data []byte) (int, error) {
	b := bytes.NewBuffer([]byte(data))
	res, err := http.Post(cl.url+"/log", "text/plain", b)
	if err != nil {
		return 0, err
	}
	if res.StatusCode != http.StatusOK {
		return 0, fmt.Errorf("Failed to send log message. Service responded with %d - %s", res.StatusCode, res.Status)
	}
	return len(data), nil
}

主启动程序LogService

启动服务Logservice,主要执行start方法，里面有细节实现服务注册与服务发现

package main
import (
	"context"
	"distributed/log"
	"distributed/registry"
	"distributed/service"
	"fmt"
	stlog "log"
)
func main() {
  // 初始化启动一个日志文件对象
	log.Run("./distributed.log")
  // 日志服务注册的端口和地址
	host, port := "localhost", "4000"
	serviceAddress := fmt.Sprintf("http://%s:%s", host, port)
  // 初始化注册对象
	r := registry.Registration{
		ServiceName:      registry.LogService, // 自身服务名
		ServiceURL:       serviceAddress,  // 自身服务地址
		RequiredServices: make([]registry.ServiceName, 0),// 依赖服务
		ServiceUpdateURL: serviceAddress + "/services", // 服务列表
		HeartbeatURL: serviceAddress + "/heartbeat",  // 心跳
	}
  // 启动日志服务包含服务注册,发现等细节
	ctx, err := service.Start(
		context.Background(),
		host,
		port,
		r,
		log.RegisterHandlers,
	)
  // 异常写入到日志中
	if err != nil {
		stlog.Fatalln(err)
	}
  // 超时停止退出服务
	<-ctx.Done()
	fmt.Println("Shutting down log service.")
}

服务启动与注册

service/service.go

Start 启动服务的主方法


func Start(ctx context.Context, host, port string,
	reg registry.Registration,
	registerHandlersFunc func()) (context.Context, error) {
	registerHandlersFunc()  // 启动注册方法
	// 启动服务
	ctx = startService(ctx, reg.ServiceName, host, port)
	// 注册服务
	err := registry.RegisterService(reg)
	if err != nil {
		return ctx, err
	}
	return ctx, nil
}

startService

func startService(ctx context.Context, serviceName registry.ServiceName,
	host, port string) context.Context {
	ctx, cancel := context.WithCancel(ctx)
	var srv http.Server
	srv.Addr = ":" + port
	// 该协程为监听http服务，并且停止服务的时候cancel
	go func() {
		log.Println(srv.ListenAndServe())
		// 删除对应的服务
		err := registry.ShutdownService(fmt.Sprintf("http://%s:%s", host, port))
		if err != nil {
			log.Println(err)
		}
		cancel()
	}()
	// 该协程为监听手动停止服务的信号
	go func() {
		fmt.Printf("%v started. Press any key to stop. \n", serviceName)
		var s string
		fmt.Scanln(&s)
		err := registry.ShutdownService(fmt.Sprintf("http://%s:%s", host, port))
		if err != nil {
			log.Println(err)
		}
		srv.Shutdown(ctx)
		cancel()
	}()
	return ctx
}

服务注册与发现

registry/client.go

注册服务的时候会连着心跳以及服务更新的方法一起注册！

而服务更新里面的细节就是自己自定义了一个Handler然后ServeHttp方法里面去update全局的服务提供对象,

update主要是更新服务和删除服务的最新消息

然后就是提供一个注销服务的方法

package registry
import (
	"bytes"
	"encoding/JSON"
	"fmt"
	"log"
	"math/rand"
	"net/http"
	"net/url"
	"sync"
)
// 注册服务
func RegisterService(r Registration) error {
	// 获得心跳地址并注册
	heartbeatURL, err := url.Parse(r.HeartbeatURL)
	if err != nil {
		return err
	}
	http.HandleFunc(heartbeatURL.Path, func (w http.ResponseWriter, r *http.Request)  {
		w.WriteHeader(http.StatusOK)
	})
   // 获得服务更新地址，并且自定义http服务的handler，因为每次更新服务的时候，可以在ServeHttp方法里面去维护
	serviceUpdateURL, err := url.Parse(r.ServiceUpdateURL)
	if err != nil {
		return err
	}
	http.Handle(serviceUpdateURL.Path, &serviceUpdateHanlder{})
    // 写入buf值将服务对象发送给注册中心的services地址
	buf := new(bytes.Buffer)
	enc := json.NewEncoder(buf)
	err = enc.Encode(r)
	if err != nil {
		return err
	}
	res, err := http.Post(ServicesURL, "application/json", buf)
	if err != nil {
		return err
	}
	if res.StatusCode != http.StatusOK {
		return fmt.Errorf("Failed to register service. Registry service "+
			"responded with code %v", res.StatusCode)
	}
	return nil
}
type serviceUpdateHanlder struct{}
func (suh serviceUpdateHanlder) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}
	dec := json.NewDecoder(r.Body)
	var p patch
	err := dec.Decode(&p)
	if err != nil {
		log.Println(err)
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	fmt.Printf("Updated received %v\n", p)
	prov.Update(p) // 更新服务提供对象
}
// 删除对应注册中心的服务地址
func ShutdownService(url string) error {
	req, err := http.NewRequest(http.MethodDelete, ServicesURL,
		bytes.NewBuffer([]byte(url)))
	if err != nil {
		return err
	}
	req.Header.Add("Content-Type", "text/plain")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	if res.StatusCode != http.StatusOK {
		return fmt.Errorf("Failed to deregister service. Registry "+
			"service responded with code %v", res.StatusCode)
	}
	return nil
}
// 更新服务列表
func (p *providers) Update(pat patch) {
	p.mutex.Lock()
	defer p.mutex.Unlock()
    // 将patch中有新增的进行添加
	for _, patchEntry := range pat.Added {
		if _, ok := p.services[patchEntry.Name]; !ok {
			p.services[patchEntry.Name] = make([]string, 0)
		}
		p.services[patchEntry.Name] = append(p.services[patchEntry.Name],
			patchEntry.URL)
	}
    // 将patch中被标记删除的
	for _, patchEntry := range pat.Removed {
		if providerURLs, ok := p.services[patchEntry.Name]; ok {
			for i := range providerURLs {
				if providerURLs[i] == patchEntry.URL {
					p.services[patchEntry.Name] = append(providerURLs[:i],
						providerURLs[i+1:]...)
				}
			}
		}
	}
}
// 根据服务名负载均衡随机获取服务地址
func (p providers) get(name ServiceName) (string, error) {
	providers, ok := p.services[name]
	if !ok {
		return "", fmt.Errorf("No providers available for service %v", name)
	}
	idx := int(rand.Float32() * float32(len(providers)))
	return providers[idx], nil
}
// 对外暴露生产者的方法
func GetProvider(name ServiceName) (string, error) {
	return prov.get(name)
}
type providers struct {
	services map[ServiceName][]string
	mutex    *sync.RWMutex
}
// 服务提供对象
var prov = providers{
	services: make(map[ServiceName][]string),  // 服务列表  服务名->集群地址集合
	mutex:    new(sync.RWMutex),  // 锁  防止服务注册更新时的并发情况
}

registry/registration.go

主要是一些关于服务使用到的参数以及对象!

package registry
type Registration struct {
	ServiceName      ServiceName   // 服务名
	ServiceURL       string        // 服务地址
	RequiredServices []ServiceName // 依赖的服务
	ServiceUpdateURL string        // 服务更新的地址
	HeartbeatURL     string        // 心跳地址
}
type ServiceName string
// 服务名集合
const (
	LogService     = ServiceName("LogService")
	GradingService = ServiceName("GradingService")
	PortalService  = ServiceName("Portald")
)
// 服务对象参数
type patchEntry struct {
	Name ServiceName
	URL  string
}
// 更新的服务对象参数  
type patch struct {
	Added   []patchEntry
	Removed []patchEntry
}

registry/server.go

服务端的注册中心服务的增删改查管理以及心跳检测，及时将最新的更新的服务消息通知回给客户端

package registry
import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"sync"
	"time"
)
const ServerPort = ":3000"
const ServicesURL = "http://localhost" + ServerPort + "/services"   // 注册中心地址
// 服务对象集合
type registry struct {
	registrations []Registration
	mutex         *sync.RWMutex
}
// 添加服务
func (r *registry) add(reg Registration) error {
	r.mutex.Lock()
	r.registrations = append(r.registrations, reg)
	r.mutex.Unlock()
	err := r.sendRequiredServices(reg)
	r.notify(patch{
		Added: []patchEntry{
			patchEntry{
				Name: reg.ServiceName,
				URL:  reg.ServiceURL,
			},
		},
	})
	return err
}
// 通知服务接口请求去刷新改变后到服务
func (r registry) notify(fullPatch patch) {
	r.mutex.RLock()
	defer r.mutex.RUnlock()
	for _, reg := range r.registrations {
		go func(reg Registration) {
			for _, reqService := range reg.RequiredServices {
				p := patch{Added: []patchEntry{}, Removed: []patchEntry{}}
				sendUpdate := false
				for _, added := range fullPatch.Added {
					if added.Name == reqService {
						p.Added = append(p.Added, added)
						sendUpdate = true
					}
				}
				for _, removed := range fullPatch.Removed {
					if removed.Name == reqService {
						p.Removed = append(p.Removed, removed)
						sendUpdate = true
					}
				}
				if sendUpdate {
					err := r.sendPatch(p, reg.ServiceUpdateURL)
					if err != nil {
						log.Println(err)
						return
					}
				}
			}
		}(reg)
	}
}
// 更新每个服务的依赖服务
func (r registry) sendRequiredServices(reg Registration) error {
	r.mutex.RLock()
	defer r.mutex.RUnlock()
	var p patch
	for _, serviceReg := range r.registrations {
		for _, reqService := range reg.RequiredServices {
			if serviceReg.ServiceName == reqService {
				p.Added = append(p.Added, patchEntry{
					Name: serviceReg.ServiceName,
					URL:  serviceReg.ServiceURL,
				})
			}
		}
	}
	err := r.sendPatch(p, reg.ServiceUpdateURL)
	if err != nil {
		return err
	}
	return nil
}
// 告诉客户端更新，最新的服务列表是这个
func (r registry) sendPatch(p patch, url string) error {
	d, err := json.Marshal(p)
	if err != nil {
		return err
	}
	_, err = http.Post(url, "application/json", bytes.NewBuffer(d))
	if err != nil {
		return err
	}
	return nil
}
// 注册中心删除服务对象
func (r *registry) remove(url string) error {
	for i := range reg.registrations {
		if reg.registrations[i].ServiceURL == url {
			// 通知客户端更新对象信息
			r.notify(patch{
				Removed: []patchEntry{
					{
						Name: r.registrations[i].ServiceName,
						URL:  r.registrations[i].ServiceURL,
					},
				},
			})
			r.mutex.Lock()
			reg.registrations = append(reg.registrations[:i], reg.registrations[i+1:]...)
			r.mutex.Unlock()
			return nil
		}
	}
	return fmt.Errorf("Service at URL %s not found", url)
}
// 心跳检测
func (r *registry) heartbeat(freq time.Duration) {
	for {
		var wg sync.WaitGroup
		for _, reg := range r.registrations {
			wg.Add(1)
			go func(reg Registration) {
				defer wg.Done()
				success := true
				for attemps := 0; attemps < 3; attemps++ {
					res, err := http.Get(reg.HeartbeatURL)
					if err != nil {
						log.Println(err)
					} else if res.StatusCode == http.StatusOK {
						log.Printf("Heartbeat check passed for %v", reg.ServiceName)
						// 如果心跳恢复了，把服务重新注册回来
						if !success {
							r.add(reg)
						}
						break;
					}
					// 如果执行到这就代表着心跳没有响应，那就代表着需要回收注销该服务了
					log.Printf("Heartbeat check failed for %v", reg.ServiceName)
					if success {
						success = false
						r.remove(reg.ServiceURL)
					}
					time.Sleep(1 * time.Second)
				}
			}(reg)
			wg.Wait()
			time.Sleep(freq)
		}
	}
}
var once sync.Once
func SetupRegistryService() {
	// 保证执行一次进行服务到心跳 每三秒循环一遍
	once.Do(func() {
		go reg.heartbeat(3 * time.Second)
	})
}
var reg = registry{
	registrations: make([]Registration, 0),
	mutex:         new(sync.RWMutex),
}
type RegistryService struct{}
func (s RegistryService) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	log.Println("Request received")
	switch r.Method {
	case http.MethodPost:
		dec := json.NewDecoder(r.Body)
		var r Registration
		err := dec.Decode(&r)
		if err != nil {
			log.Println(err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		log.Printf("Adding service: %v with URL: %s\n", r.ServiceName,
			r.ServiceURL)
		err = reg.add(r)
		if err != nil {
			log.Println(err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}
	case http.MethodDelete:
		payload, err := ioutil.ReadAll(r.Body)
		if err != nil {
			log.Println(err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		url := string(payload)
		log.Printf("Removing service at URL: %s", url)
		err = reg.remove(url)
		if err != nil {
			log.Println(err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}
}

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