package main
import (
"fmt"
"net"
"os"
"time"
)
const (
MAX_CONN_NUM = 5
)
//echo server Goroutine
func EchoFunc(conn net.Conn) {
defer conn.Close()
buf := make([]byte,1024)
for {
_,err := conn.Read(buf)
if err != nil {
//println("Error reading:",err.Error())
return
}
//send reply
_,err = conn.Write(buf)
if err != nil {
//println("Error send reply:",err.Error())
return
}
}
}
//initial listener and run
func main() {
listener,err := net.Listen("tcp","0.0.0.0:8088")
if err != nil {
fmt.Println("error listening:",err.Error())
os.Exit(1)
}
defer listener.Close()
fmt.Printf("running ...\n")
var cur_conn_num int = 0
conn_chan := make(chan net.Conn)
ch_conn_change := make(chan int)
go func() {
for conn_change := range ch_conn_change {
cur_conn_num += conn_change
}
}()
go func() {
for _ = range time.Tick(1e8) {
fmt.Printf("cur conn num: %f\n",cur_conn_num)
}
}()
for i := 0; i < MAX_CONN_NUM; i++ {
go func() {
for conn := range conn_chan {
ch_conn_change <- 1
EchoFunc(conn)
ch_conn_change <- -1
}
}()
}
for {
conn,err := listener.Accept()
if err != nil {
println("Error accept:",err.Error())
return
}
conn_chan <- conn
}
}
再看这段代码使用传统思维实行方式：
//
//A echo server with max-connections limit and interval connection show
//
package main
import (
"fmt"
"net"
"os"
"time"
)
const (
MAX_CONN_NUM = 5
)
//echo server Goroutine
func EchoFunc(conn net.Conn,conn_close_flag chan int) {
defer conn.Close()
defer func() {
conn_close_flag <- -1
}()
buf := make([]byte,1024)
for {
_,err := conn.Read(buf)
if err != nil {
//println("Error reading:",err.Error())
return
}
//send reply
_,err = conn.Write(buf)
if err != nil {
//println("Error send reply:",err.Error())
return
}
}
}
//initial listener and run
func main() {
listener,"0.0.0.0:8088")
if err != nil {
println("error listening:",err.Error())
os.Exit(1)
}
defer listener.Close()
fmt.Printf("running ...\n")
var cur_conn_num float64 = 0
ch_conn_change := make(chan int,MAX_CONN_NUM)
tick := time.Tick(1e8)
for {
//read all close flags berfor accept new connection
//TODO: better code to handle batch close?
readmore := 1
for readmore > 0 {
select {
case conn_change := <-ch_conn_change:
cur_conn_num = cur_conn_num + float64(conn_change)
default:
readmore = 0
}
}
//FIXME: tick block by listener.Accept()
select {
case <-tick:
fmt.Printf("cur conn num: %f\n",cur_conn_num)
default:
}
if cur_conn_num >= MAX_CONN_NUM {
//reach MAX_CONN_NUM,waiting for exist connection close
time.Sleep(time.Second)
} else {
//accept new connetion
conn,err := listener.Accept()
if err != nil {
println("Error accept:",err.Error())
return
}
cur_conn_num++
go EchoFunc(conn,ch_conn_change)
}
}
}
这个案例中，golang通过多个goroutine + channel堵塞做到传统的顺序执行模式。
代码来自google group的讨论：https://groups.google.com/forum/#!topic/golang-china/q4pFH-AGnfs
