目录
1.建立长连接
2.后端主动通知前端消息
3.调试
4.关闭长连接
项目需求:在go项目中实现SSE长连接,耗时操作完成后,后端主动通知前端消息。
1.建立长连接
最主要的操作是修改请求中的Content-Type类型为"text/event-stream"。
需要注意几点,后端首先不能让请求处理代码跑完,如果跑完这个请求就会断掉,保存的*gin.Context信息也就没用了,因此要新建一个range chan维持处理状态。
另外这里如果用for循环代替chan,会导致前端持续发送请求到后端。
import (
"encoding/json"
"fmt"
"github.com/gin-gonic/gin"
"github.com/labstack/gommon/log"
"net/http"
"strings"
"time"
)
var ifChannelsMapInit = false
var channelsMap = map[string]chan string{}
func initChannelsMap() {
channelsMap = make(map[string]chan string)
}
func AddChannel(userEmail string, traceId string) {
if !ifChannelsMapInit {
initChannelsMap()
ifChannelsMapInit = true
}
var newChannel = make(chan string)
channelsMap[userEmail+traceId] = newChannel
log.Infof("Build SSE connection for user = " + userEmail + ", trace id = " + traceId)
}
func BuildNotificationChannel(userEmail string, traceId string, c *gin.Context) {
AddChannel(userEmail, traceId)
c.Writer.Header().Set("Content-Type", "text/event-stream")
c.Writer.Header().Set("Cache-Control", "no-cache")
c.Writer.Header().Set("Connection", "keep-alive")
w := c.Writer
flusher, _ := w.(http.Flusher)
closeNotify := c.Request.Context().Done()
go func() {
<-closeNotify
delete(channelsMap, userEmail+traceId)
log.Infof("SSE close for user = " + userEmail + ", trace id = " + traceId)
return
}()
fmt.Fprintf(w, "data: %s\n\n", "--ping--")
flusher.Flush()
for msg := range channelsMap[userEmail+traceId] {
fmt.Fprintf(w, "data: %s\n\n", msg)
flusher.Flush()
}
}
2.后端主动通知前端消息
当耗时操作处理完成后,调用该方法,前端会收到通知。
func SendNotification(userEmail string, messageBody string, actionType string) {
log.Infof("Send notification to user = " + userEmail)
var msg = dao.NotificationLog{}
msg.MessageBody = messageBody
msg.UserEmail = userEmail
msg.Type = actionType
msg.Status = UNREAD
msg.CreateTime = time.Now()
msg.Create()
msgBytes, _ := json.Marshal(msg)
for key := range channelsMap {
if strings.Contains(key, userEmail) {
channel := channelsMap[key]
channel <- string(msgBytes)
}
}
}
3.调试
准备两个接口,分别是建立SSE和触发耗时操作
GroupV1Rest.GET("/notification/socket-connection", controllers.SocketConnection)
GroupV1Rest.GET("/notification/export-excel", controllers.ExportExcel)
打开浏览器,进入调试模式,在console页输入
e = new EventSource('/business/v1/notification/socket-connection');
e.onmessage = function(event) {
console.log(event.data);
};
看到日志打印‘--ping--’,长连接已建立
此时发送第二个请求,调试模式看到通知被chan处理
返回浏览器,可以看到已经收到通知
4.关闭长连接
前端关闭页面后,自动触发监听事件,后端清理连接信息文章来源:https://www.uudwc.com/A/GdpNd/
文章来源地址https://www.uudwc.com/A/GdpNd/