Fiber: 🤔 Server Sent Events

[bashery]

Question description

Would providing sse as a Middleware -or any plugin type - be a good idea for fiber?. I think it would be useful for some cases covered by websocket are a lot complicated and resource consumption

[Fenny]

Hi @bashery, sorry for the late reply! I personally never worked with SSE, but we are willing to add this to our middleware list if you made one 👍

I'm closing this issue, for now, feel free to re-open if you have suggestions/questions or any updates regarding this matter 👌

[rafaelgfirmino]

This issue is close, but I can use fiber and Server-Sent Events using a gofiber/adaptor

Example:

//main.go
package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "github.com/gofiber/adaptor/v2"
    "github.com/gofiber/fiber/v2"
    "math/rand"
    "net/http"
    "time"
)

type (
    Client struct {
        name   string
        events chan *DashBoard
    }
    DashBoard struct {
        User uint
    }
)

func main() {
    app := fiber.New()
    app.Get("/sse/validation", adaptor.HTTPHandler(handler(dashbaordHandler)))
    app.Listen(":3000")
}

func handler(f http.HandlerFunc) http.Handler {
    return http.HandlerFunc(f)
}
func dashbaordHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Println("Client: %v", r.RemoteAddr)
    client := &Client{name: r.RemoteAddr, events: make(chan *DashBoard, 10)}
    go updateDashboard(client)

    w.Header().Set("Access-Control-Allow-Origin", "*")
    w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
    w.Header().Set("Content-Type", "text/event-stream")
    w.Header().Set("Cache-Control", "no-cache")
    w.Header().Set("Connection", "keep-alive")

    timeout := time.After(1 * time.Second)
    select {
    case ev := <-client.events:
        var buf bytes.Buffer
        enc := json.NewEncoder(&buf)
        enc.Encode(ev)
        fmt.Fprintf(w, "data: %v\n\n", buf.String())
        fmt.Printf("data: %v\n", buf.String())
    case <-timeout:
        fmt.Fprintf(w, ": nothing to sent\n\n")
    }

    if f, ok := w.(http.Flusher); ok {
        f.Flush()
    }
}

func updateDashboard(client *Client) {
    for {
        db := &DashBoard{
            User:         uint(rand.Uint32()),
        }
        client.events <- db
    }
}

call this function in you HTML page

//js file
export default function onLoad() {
    var source = new EventSource("http://localhost:3000/sse/validation")
    source.onmessage = (event) => {
        console.log("OnMessage Called:")
        console.log(event)
        console.log(JSON.parse(event.data))
    }
}