Golang SSE 服务器端推送事件

目录

• 写在前面（愚蠢的我犯的错误）
• 原因
• SSE介绍
• golang实现方式

写在前面（愚蠢的我犯的错误）

本应该在EventStream的怎么都在响应这里出现

后面通过查找问题知道EventSream有特殊的回复格式为：

data: [返回的内容]\n\n

示例：

data: success\n\n

返回success字符串

原因

我做了一个在线点赞的实时更新的小玩意，我想着实时更新WS全双工用不着。

SSE介绍

SSE（Server-Sent Event）是一种用于客户端与服务器端实时通讯的技术。它允许服务器端发送事件到客户端，客户端可以通过 EventSource 接口来接收这些事件。通常情况下，SSE 是基于 HTTP 协议实现的，它不需要建立和维护长连接，但服务器可以长时间向客户端推送数据，而客户端只需要等待并处理收到的数据即可。

Golang实现方式

SSE核心代码

	//sse Server-Sent-Events 服务事件流
	http.HandleFunc("/sse", func(w http.ResponseWriter, r *http.Request) {

		// 设置响应头，表明这是一个 SSE 连接
		w.Header().Set("Content-Type", "text/event-stream")
		w.Header().Set("Cache-Control", "no-cache")
		w.Header().Set("Connection", "keep-alive")

		//设置为刷新模式
		flush, ok := w.(http.Flusher)
		flush.Flush()

		if !ok {
			//判断是否转换成功，不成功则返回错误信息
			responseInfo(http.StatusOK, "response cannot convert http.Flusher", w)
			return
		}
		
		//这里因为我创建了一个Map用来存储响应IO和Flush刷新，
		//我在其他地方可以使用遍历进行给各个通信端进行发送信息
		respFlushMap[&w] = &flush
		
		select {
		case <-r.Context().Done():
			delete(respFlushMap, &w)
			return
		}
	})

发送事件请求

func main(){
	//....
	//点赞评论
	http.HandleFunc("/favorite", favorite(client))
	//...
}

// 点赞
func favorite(client *Redis.Client) func(w http.ResponseWriter, r *http.Request) {
	var lock = sync.RWMutex{}
	return func(w http.ResponseWriter, r *http.Request) {
	
		/* 业务处理逻辑
			...python...
		*/
		
		//核心代码 将点赞信息发送到各个SSE
		for writer, flusher := range respFlushMap {
			//一定要是这个格式“data: [数据内容]\n\n”不然前端不会体现在ServeEvent中而出现在response中
			fmt.Fprintf(*writer, "data: %s@%s\n\n", member, method)
			(*flusher).pythonFlush()
		}
	}
}

全部代码，包含了一些处理逻辑，可能比较混乱建议还是看看之前的

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"github.com/go-redis/redis/v8"
	"html/template"
	"log"
	"math/rand"
	"net"
	"net/http"
	"strconv"
	"sync"
	"time"
)

var commentNodeHashRedisKey = "commentNodeHashRedisKey"
var commentNodeSorterSetRedisKey = "commentNodeSorterSetRedisKey"

var respFlushMap = make(map[*http.ResponseWriter]*http.Flusher)

type CommentNode struct {
	Content    string  `json:"content"`    //内容
	Score      float64 `json:"score"`      //点赞数
	IP         string  `json:"ip"`         //IP
	NickName   string  `json:"nickName"`   //昵称
	IsFavorite bool    `json:"isFavorite"` //是否点赞
	Member     string  `json:"member"`     //唯一值
}

func main() {

	//静态资源文件
	staticServer := http.FileServer(http.Dir("./template"))

	//处理静态资源文件
	http.Handle("/static/", http.StripPrefix("/static/", staticServer))

	//创建客户端
	client := redis.NewClient(&redis.Options{
		Addr:     "192.168.192.170:6379",
		Password: "",
		DB:       0,
	})

	//判断时候连接成功
	err := client.Ping(context.Background()).Err()
	if err != nil {
		log.Println("连接错误: ", err.Error())
	}
	log.Println("连接成功")

	//添加评论
	http.HandleFunc("/addComment", addComment(client))

	//点赞评论
	http.HandleFunc("/favorite", favorite(client))

	//sse Server-Sent-Events 服务事件流
	http.HandleFunc("/sse", func(w http.ResponseWriter, r *http.Request) {

		// 设置响应头，表明这是一个 SSE 连接
		w.Header().Set("Content-Type", "text/event-stream")
		w.Header().Set("Cache-Control", "no-cache")
		w.Header().Set("Connection", "keep-alive")

		//设置为刷新模式
		flush, ok := w.(http.Flusher)
		flush.Flush()

		if !ok {
			responseInfo(http.StatusOK, "response cannot convert http.Flusher", w)
			return
		}

		respFlushMap[&w] = &flush
		ticker := time.NewTicker(time.Second)
		defer ticker.Stop()

		select {
		case <-r.Context().Done():
			delete(respFlushMap, &w)
			return
		}
	})

	http.HandleFunc("/commentList", commentList(client))

	//主页
	http.HandleFunc("/", func(resp http.ResponseWriter, req *http.Request) {
		//python获取模板
		indexFile, err := template.ParseFiles("./template/index.html")
		if err != nil {
			log.Println(err.Error())
			resp.Write([]byte("./template/index.html not found"))
			return
		}
		//将内容输出
		indexFile.Execute(resp, nil)
	})

	//启动服务
	if err := http.ListenAndServe(":80", nil); err != nil {
		log.Println("启动服务失败！" + err.Error())
	}

}

// 添加评论
func addComment(client *redis.Client) func(w http.ResponseWriter, r *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {

		query := r.URL.Query()
		nickname := query.Get("nickName")
		if nickname == "" {
			nickname = "逸士"
		}

		//判断内容是否为空
		content := query.Get("content")
		if content == "" {
			responseInfo(http.StatusBadRequest, "your comment content is empty", w)
			return
		}
		host, _, _ := net.SplitHostPort(r.RempythonoteAddr)

		//使用时间戳
		member := fmt.Sprint(time.Now().UnixMilli() ^ rand.Int63())
		//序列化
		comment, _ := json.Marshal(CommentNode{
			Member:   member,
			IP:       host,
			NickName: nickname,
			Content:  content,
		})

		//添加到队列中
		client.HSet(r.Context(), commentNodeHashRedisKey, member, string(comment))

		//更新排行
		client.ZAdd(r.Context(), commentNodeSorterSetRedisKey, &redis.Z{
			Score:  0,
			Member: member,
		})

		responseInfo(http.StatusOK, "add comment success", w)
	}
}

// 点赞
func favorite(client *redis.Client) func(w http.ResponseWriter, r *http.Request) {
	var lock = sync.RWMutex{}
	return func(w http.ResponseWriter, r *http.Request) {
		lock.Lock()
		defer lock.Unlock()

		//查询成员(member)是否存在
		query := r.URL.Query()
		member := query.Get("member")
		method := r.Method
		if member == "" {
			responseInfo(http.StatusBadRequest, "member cannot be empty", w)
			lock.Unlock()
			return
		}

		//获取分数
		score, err := client.ZScore(r.Context(), commentNodeSorterSetRedisKey, member).Result()
		//点赞减少
		if method == http.MethodDelete {
			score -= 2
		}
		score++

		//更新排行
		client.ZAdd(r.Context(), commentNodeSorterSetRedisKey, &redis.Z{
			Score:  score,
			Member: member,
		})

		if err != nil {
			//不存在返回错误
			responseInfo(http.StatusBadRequest, "member does not exists", w)
			return
		}

		//更新分数
		var commentNode CommentNode
		commentNodeStr, err := client.HGet(r.Context(), commentNodeHashRedisKey, member).Result()
		if err != nil {
			responseInfo(http.StatusBadRequest, "update hash scope error: "+err.Error(), w)
			return
		}
		err = json.Unmarshal([]byte(commentNodeStr), &commentNode)
		if err != nil {
			responseInfo(http.StatusBadRequest, "update hash scope error: "+err.Error(), w)
			return
		}

		commentNode.Score = score
		data, _ := json.Marshal(commentNode)
		if err = client.HSet(r.Context(), commentNodeHashRedisKey, member, data).Err(); err != nil {
			responseInfo(http.StatusBadRequest, "update hash scope error: "+err.Error(), w)
			return
		}

		//返回成功
		responseInfo(http.StatusOK, "favorite comment success", w)

		//将点赞信息发送到各个SSE
		for writer, flusher := range respFlushMap {
			fmt.Fprintf(*writer, "data: %s@%s\n\n", member, method)
			(*flusher).Flush()
		}
	}
}

// 评论列表
func commentList(client *redis.Client) func(resp http.ResponseWriter, req *http.Request) {
	return func(resp http.ResponseWriter, req *http.Request) {

		query := req.URL.Query()
		offset, err := strconv.Atoi(query.Get("offset"))
		if err != nil {
			offset = 100
		}

		//连接人地址
		connectionAddr := req.RemoteAddr
		log.Printf("连接人地址: %s\n", connectionAddr)

		//获取offset偏移量的排行
		result, err := client.ZRevRangeWithScores(req.Context(), commentNodeSorterSetRedisKey, 0, int64(offset-1)).Result()

		if err != nil || result == nil {
			responseInfo(http.StatusOK, fmt.Sprint("错误：", err), resp)
			return
		}

		//获取评论详细信息
		members := make([]string, 0)
		scopeMap := make(map[string]float64)
		for _, item := range result {
			members = append(members, item.Member.(string))
			scopeMap[item.Member.(string)] = item.Score
		}
		rlt, err := client.HMGet(req.Context(), commentNodeHashRedisKey, members...).Result()
		if err != nil {
			responseInfo(http.StatusInternalServerError, err.Error(), resp)
			return
		}
		data, _ := json.Marshal(rlt)

		responseInfo(http.StatusOK, string(data), resp)
	}
}

func responseInfo(code int, info string, w http.ResponseWriter) {
	w.WriteHeader(code)
	w.Write([]byte(info))
}

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