golang hijack

一直不太明白golang的hijack是干什么的?只知道hijack这个词是篡取的意思,难道跟网关的作用一样,把client的请求发到这个服务上,然后这个服务帮忙转发到远端server,但是看了源码后就明白这个golang hijack是干嘛的?

先看一下hijack相关的结构说明:

type Hijacker interface {
	Hijack() (net.Conn, *bufio.ReadWriter, error)
}
//返回连接接口net.Conn和ReadWriter,bufio读写的

// Hijack lets the caller take over the connection. -----翻译Hijack让调用者管理连接

// After a call to Hijack(), the HTTP server library

// will not do anything else with the connection.

// It becomes the caller's responsibility to manage

// and close the connection.

------------翻译调用Hijack后,HTTP的server不会对连接做多余的处理让用户自己管理和关闭连接

再看一下docker中对hijack的使用

     dial, err := cli.dial() //设置TCP keepAlive做长连接
	// When we set up a TCP connection for hijack, there could be long periods
	// of inactivity (a long running command with no output) that in certain
	// network setups may cause ECONNTIMEOUT, leaving the client in an unknown
	// state. Setting TCP KeepAlive on the socket connection will prohibit
	// ECONNTIMEOUT unless the socket connection truly is broken
	if tcpConn, ok := dial.(*net.TCPConn); ok {
		tcpConn.SetKeepAlive(true)
		tcpConn.SetKeepAlivePeriod(30 * time.Second)
	}
	if err != nil {
		if strings.Contains(err.Error(), "connection refused") {
return fmt.Errorf("Cannot connect to the Docker daemon. Is 'docker daemon' running on this host?")
		}
		return err
	}
	clientconn := httputil.NewClientConn(dial, nil) 
	defer clientconn.Close()
	// Server hijacks the connection, error 'connection closed' expected
	clientconn.Do(req)
	rwc, br := clientconn.Hijack() 
	//清理掉buffer 这步非常重要,返回这个两个参数就是给用户自己管理连接和数据处理
	defer rwc.Close()

再看看clientconn.Hijack的实现:

func (cc *ClientConn) Hijack() (c net.Conn, r *bufio.Reader) {
	cc.lk.Lock()
	defer cc.lk.Unlock()
	c = cc.c
	r = cc.r
	cc.c = nil
	cc.r = nil
	return
}
//就是在NewClientConn时候保存的net.Conn和bufio.Reader
func NewClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
	if r == nil {
		r = bufio.NewReader(c)
	}
	return &ClientConn{
		c:    c,
		r:    r,
		pipereq: make(map[*http.Request]uint),
		writeReq: (*http.Request).Write,
	}
}

总结:hijack就是不用重新建立连接或者重新构造ClientConn设置net.Conn和bufio,然后不断复用net.Conn和bufio,自己管理

本文来自:开源中国博客

感谢作者:golang_yh

查看原文:golang hijack

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