package main

import (

    "net"

    "time"

)

func initProxy() {

    pLog.Infof("Proxying %s -> %s\n", pConfig.Bind, pConfig.Backend)  //输出服务地址   后端服务地址列表  

    server, err := net.Listen("tcp", pConfig.Bind)  //建立tcp连接

    if err != nil {

        pLog.Fatal(err)

    }

    waitQueue := make(chan net.Conn, pConfig.WaitQueueLen)  //建立连接队列  队列默认等待队列长度---channel  net.Conn  ==控制最大排队队列

    availPools := make(chan bool, pConfig.MaxConn)  //建立最大连接数--channel  bool=== 控制最大连接数

    for i := 0; i < pConfig.MaxConn; i++ {  //

        availPools <- true

    }

    go loop(waitQueue, availPools)

    for {

        connection, err := server.Accept()  //等待获取下一次连接

        if err != nil {

            pLog.Error(err)

        } else {

            pLog.Infof("Received connection from %s.\n", connection.RemoteAddr())

            waitQueue <- connection

        }

    }

}

func loop(waitQueue chan net.Conn, availPools chan bool) {

    for connection := range waitQueue { //循环等待队列中 排队等待需要处理的数据--连接

        <-availPools  //从通道中 连接池中取出一个

        go func(connection net.Conn) {

            handleConnection(connection)

            availPools <- true  //使用结束放回连接池中  目的控制连接数量  通道阻塞特性

            pLog.Infof("Closed connection from %s.\n", connection.RemoteAddr())

        }(connection)

    }

}

func handleConnection(connection net.Conn) {

    defer connection.Close()

    bksvr, ok := getBackendSvr(connection)

    if !ok {

        return

    }

    remote, err := net.Dial("tcp", bksvr.svrStr)

    if err != nil {

        pLog.Error(err)

        bksvr.failTimes++

        return

    }

    //等待双向连接完成

    complete := make(chan bool, 2)

    oneSide := make(chan bool, 1)

    otherSide := make(chan bool, 1)

    go pass(connection, remote, complete, oneSide, otherSide)

    go pass(remote, connection, complete, otherSide, oneSide)

    <-complete

    <-complete

    remote.Close()

}

// copy Content two-way

func pass(from net.Conn, to net.Conn, complete chan bool, oneSide chan bool, otherSide chan bool) {

    var err error

    var read int

    bytes := make([]byte, 256)

    for {

        select {

        case <-otherSide:

            complete <- true

            return

        default:

            from.SetReadDeadline(time.Now().Add(time.Duration(pConfig.Timeout) * time.Second))

            read, err = from.Read(bytes)

            if err != nil {

                complete <- true

                oneSide <- true

                return

            }

            to.SetWriteDeadline(time.Now().Add(time.Duration(pConfig.Timeout) * time.Second))

            _, err = to.Write(bytes[:read])

            if err != nil {

                complete <- true

                oneSide <- true

                return

            }

        }

    }

}