golang net/http 源码学习分析

golang net/http 源码学习分析

golang中函数是一等公民

Server端

建立http服务

import "net/http"

func main()  {
	http.HandleFunc("/", IndexHandler)
	http.ListenAndServe(":8088",nil)
}

func IndexHandler(writer http.ResponseWriter, request *http.Request)  {
	writer.Write([]byte("hello world"))
}

http.HandleFunc构建路由

func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
	DefaultServeMux.HandleFunc(pattern, handler)
}

func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
	if handler == nil {
		panic("http: nil handler")
	}
	mux.Handle(pattern, HandlerFunc(handler))
}

func (mux *ServeMux) Handle(pattern string, handler Handler) {
	mux.mu.Lock()
	defer mux.mu.Unlock()

	if pattern == "" {
		panic("http: invalid pattern")
	}
	if handler == nil {
		panic("http: nil handler")
	}
	if _, exist := mux.m[pattern]; exist {
		panic("http: multiple registrations for " + pattern)
	}

	if mux.m == nil {
		mux.m = make(map[string]muxEntry)
	}
	e := muxEntry{h: handler, pattern: pattern}
	mux.m[pattern] = e
	if pattern[len(pattern)-1] == '/' {
		mux.es = appendSorted(mux.es, e)
	}

	if pattern[0] != '/' {
		mux.hosts = true
	}
}

Handle()会将路由URL和处理器方法注册到DefaultServeMux中，ServeMux结构如下：

type ServeMux struct {
	mu    sync.RWMutex
	m     map[string]muxEntry
	es    []muxEntry // slice of entries sorted from longest to shortest.
	hosts bool       // whether any patterns contain hostnames
}

type muxEntry struct {
	h       Handler
	pattern string
}

// NewServeMux allocates and returns a new ServeMux.
func NewServeMux() *ServeMux { return new(ServeMux) }

// DefaultServeMux is the default ServeMux used by Serve.
var DefaultServeMux = &defaultServeMux

var defaultServeMux ServeMux

http.ListenAndServe(":8088",nil)监听请求

func (srv *Server) ListenAndServe() error {
	if srv.shuttingDown() {
		return ErrServerClosed
	}
	addr := srv.Addr
	if addr == "" {
		addr = ":http"
	}
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}
	return srv.Serve(ln)
}

由net.Listen("tcp", addr)构建出tcp服务，监听设置端口，再由srv.Serve(ln)获取并处理请求。

在func (srv *Server) Serve(l net.Listener) 中由rw, err := l.Accept()接受请求，在单独的携程中处理请求 go c.serve(connCtx)

在func (c *conn) serve(ctx context.Context)中，由 w, err := c.readRequest(ctx) 读出请求内容，在serverHandler{c.server}.ServeHTTP(w, w.req) 中得到处理器，并由处理器处理请求

---

client端

package main

import (
	"fmt"
	"io/ioutil"
	"net"
	"net/http"
	"time"
)

func main() {
	//连接池
	transport := &http.Transport{
		DialContext: (&net.Dialer{
			Timeout:   30 * time.Second, //连接超时时间
			KeepAlive: 30 * time.Second, //长链接超时时间
		}).DialContext,
		MaxIdleConns:          100,              //最大空闲连接数
		IdleConnTimeout:       90 * time.Second, //空闲超时时间
		TLSHandshakeTimeout:   10 * time.Second, //tls握手超时时间
		ExpectContinueTimeout: 1 * time.Second,  //100-continue状态码超时时间
	}

	client := &http.Client{
		Timeout:   30 * time.Second,
		Transport: transport,
	}

	resp, err := client.Get("127.0.0.1:8088")
	if err!=nil{
		panic(err)
	}
	defer resp.Body.Close()

	all, err := ioutil.ReadAll(resp.Body)

	if err!=nil{
		panic(err)
	}

	fmt.Println(all)
}

会在  func (c *Client) do(req *Request) 中调用 c.send(req, deadline)

func (c *Client) send(req *Request, deadline time.Time) (resp *Response, didTimeout func() bool, err error) {
	if c.Jar != nil {
		for _, cookie := range c.Jar.Cookies(req.URL) {
			req.AddCookie(cookie)
		}
	}
	resp, didTimeout, err = send(req, c.transport(), deadline)
	if err != nil {
		return nil, didTimeout, err
	}
	if c.Jar != nil {
		if rc := resp.Cookies(); len(rc) > 0 {
			c.Jar.SetCookies(req.URL, rc)
		}
	}
	return resp, nil, nil
}

在send方法中由 RoundTripper.RoundTrip(req) 发起请求，并得到response

---

Transport

Transport结构体主要属性

type Transport struct {
    idleMu       sync.Mutex //
    closeIdle    bool //用户是否已请求关闭所有空闲连接
    idleConn     map[connectMethodKey][]*persistConn//保存从connect到persistConn的映射
}

type connectMethodKey struct {
	proxy string, //代理url，浏览器透明代理
    scheme string, //协议 http https
    addr string // 代理base的url，下游服务base地址
	onlyH1  bool // 是否http1.1
}

func (t *Transport) RoundTrip(req *Request) (*Response, error) {
	return t.roundTrip(req)
}

func (t *Transport) roundTrip(req *Request) (*Response, error)中

pconn, err := t.getConn(treq, cm) 获取持久化连接

persistConn结构体

type persistConn struct {
    br        *bufio.Reader       // from conn
	bw        *bufio.Writer       // to conn
    reqch     chan requestAndChan  //read by readLoop
    writech   chan writeRequest    //read by writeLoop
}

t.getConn流程：

1.trace.GotConn(pc.gotIdleConnTrace(pc.idleAt)) 尝试获取空闲的连接

2.获取不到 t.queueForDial(w) -->  go t.dialConnFor(w) 开启一个协程新建一个连接

3.select  case 监听事件:监听连接是否重建成功,如果连接创建成功则返回该新建的连接,其他则返回空

最终调用getConn获得的连接的roundTrip方法

pconn.roundTrip(treq) --> pc.writech <- writeRequest{req, writeErrCh, continueCh} 

Transport RoundTrip基本流程