long_polling.go

package main

import (
	"container/list"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"os/signal"
	"runtime"
	"syscall"
	"time"
)

var (
	addr = flag.String("addr", ":7000", "Server port")
)

func ChannelsKeeper(clients chan chan string) {
	channels := list.New()
	go func() {
		for {
			select {
			case c := <-clients:
				channels.PushBack(c)
				fmt.Printf("New client: %d\n", channels.Len())
			}
		}
	}()
}

func InstallSignalHandlers(signals chan os.Signal) {
	go func() {
		sig := <-signals
		switch sig {
		case syscall.SIGINT:
			fmt.Printf("\nCtrl-C signalled\n")
			os.Exit(0)
		}
	}()
}

func CreatePidfile() {
	pid := []byte(fmt.Sprintf("%d", os.Getpid()))
	ioutil.WriteFile("long_polling.pid", pid, 0755)
}

func MakeLPHandler(clients chan chan string) func(w http.ResponseWriter, r *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		message := make(chan string, 1)
		clients <- message

		select {
		case <-time.After(60e9):
			io.WriteString(w, "Timeout!\n")
		case msg := <-message:
			io.WriteString(w, msg)
		}
	}
}

func CreateHttpServer(clients chan chan string) {
	http.HandleFunc("/", MakeLPHandler(clients))
	log.Println("Listen On" + *addr)
	err := http.ListenAndServe(*addr, nil)
	if err != nil {
		log.Fatal("ListenAndServe: ", err.Error())
	}
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU()*2 + 1)
	flag.Parse()

	clients := make(chan chan string, 1)
	signals := make(chan os.Signal, 1)
	signal.Notify(signals, syscall.SIGINT, syscall.SIGUSR1)

	CreatePidfile()
	ChannelsKeeper(clients)
	InstallSignalHandlers(signals)
	CreateHttpServer(clients)
}

test.go

package main

import (
	"flag"
	"fmt"
	"net"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"
)

var (
	nurl *url.URL
	u    = flag.String("url", "http://127.0.0.1:7000/", "Connection URL")
	c    = flag.Int("c", 10000, "Connection Count")
)

func Connect() {
	req := http.Request{
		Method: "GET",
		Header: http.Header{},
		URL:    nurl,
	}
	for {
		dial, err := net.Dial("tcp", nurl.Host)
		if err != nil {
			fmt.Println(err)
			return
		}
		conn := httputil.NewClientConn(dial, nil)
		conn.Do(&req)
		conn.Close()
	}
}

func main() {
	flag.Parse()
	nurl, _ = url.Parse(*u)
	for i := 0; i < *c; i++ {
		go Connect()
	}
	time.Sleep(1e10)
}