limited-concurrency.go

package main

import (
	"flag"
	"net"
	"os"
	"time"

	"github.com/singchia/go-hammer/circulinker"
)

func main() {
	var addr string
	flag.StringVar(&addr, "addr", ":1202", "listen addr")
	flag.Parse()

	l, err := net.Listen("tcp", addr)
	if err != nil {
		os.Exit(1)
	}
	defer l.Close()

	connMap := make(map[net.Conn]circulinker.CircuID)
	cl := circulinker.NewCirculinker()

	for i := 0; i < 100; i++ {
		go func() {
			buf := make([]byte, 1024)
			for {
				time.Sleep(time.Microsecond * 50)
				if len(connMap) == 0 {
					continue
				}

				cl.Rightshift()
				conn := cl.RetrieveCur().(net.Conn)
				conn.SetReadDeadline(time.Now().Add(time.Microsecond * 50))
				len, err := conn.Read(buf)
				E, ok := err.(net.Error)
				if ok && E.Timeout() {
					continue
				}
				if err != nil {
					conn.Close()
					cl.Delete(connMap[conn])
					delete(connMap, conn)
					continue
				}
				conn.Write(append([]byte(addr+" "), buf[:len]...))
			}

		}()
	}

	for {
		conn, err := l.Accept()
		if err != nil {
			os.Exit(1)
		}
		id := cl.Add(conn)
		connMap[conn] = id
	}
}