Example Upstream

upstream.go

package main

import (
	"fmt"
	"io"
	"math"
	"net/http"
	"net/http/httputil"
	"strconv"
	"strings"
	"time"
)

var (
	server *http.Server
)

func handler(w http.ResponseWriter, r *http.Request) {
	io.WriteString(w, "hello, world!!!\n")
}

// By default, it returns 5 chunks, one per second
// /chunked?interval=500ms to change the interval
// /chunked?infinite=true to change to return infinite number of chunks
// /chunked?size_bytes=1000 to change the size of chunk.
func chunkedHandler(w http.ResponseWriter, r *http.Request) {
	requestDump, _ := httputil.DumpRequest(r, true)
	fmt.Printf("%s", string(requestDump))
	flusher, ok := w.(http.Flusher)
	if !ok {
		panic("expected http.ResponseWriter to be an http.Flusher")
	}
	interval := time.Second
	if in := r.URL.Query().Get("interval"); in != "" {
		if d, err := time.ParseDuration(in); err == nil {
			interval = d
		}
	}
	var count int64
	count = 5
	if r.URL.Query().Get("infinite") != "" {
		count = math.MaxInt64
	}
	fixedSizeChunk := ""
	if sz := r.URL.Query().Get("size_bytes"); sz != "" {
		if i, err := strconv.Atoi(sz); err == nil {
			fixedSizeChunk = strings.Repeat("a", i)
		}
	}
	fmt.Printf("[%v] send a chunk every %v for %d times\n", time.Now(), interval, count)
	if fixedSizeChunk != "" {
		fmt.Printf("[%v] fixed size chunk is set to %d\n", time.Now(), len(fixedSizeChunk))
	}
	var i int64
	for ; i < count; i++ {
		chunk := fmt.Sprintf("[%v] Chunk #%d\n", time.Now(), i)
		if fixedSizeChunk != "" {
			chunk = fixedSizeChunk
		}
		//fmt.Printf("%s", chunk)
		if _, err := fmt.Fprintf(w, "%s", chunk); err != nil {
			fmt.Printf("failed to flush the chunk: %s\n", chunk)
			return
		}
		flusher.Flush() // Trigger "chunked" encoding and send a chunk...
		time.Sleep(interval)
	}
	fmt.Printf("[%v] %d chunks were sent.\n", time.Now(), count)
}

func main() {
	http.HandleFunc("/", handler)
	http.HandleFunc("/chunked", chunkedHandler)
	server = &http.Server{Addr: ":8080"}
	fmt.Printf("[%v] Start listening ...\n", time.Now())
	server.ListenAndServe()
}