【go语言http2.0server源码分析】

前面分析了http2.0的实现和http2.0中的client中的源码实现这里看一下server端的实现。

package main

import (
	"fmt"
	"net/http"
	"os"
	"runtime"
	"strings"
)

type textHandler struct {
	responseText string
}

func (th *textHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, th.responseText)
}

type indexHandler struct{}

func (ih *indexHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain")
	w.Write([]byte("Hello"))
}

func main() {
	mux := http.NewServeMux()
	_, fp, _, _ := runtime.Caller(0)
	dir := getParentDirectory(fp)

	mux.Handle("/", &indexHandler{})

	thWelcome := &textHandler{"TextHandler !"}
	mux.Handle("/text", thWelcome)

	err := http.ListenAndServeTLS(":8084", fmt.Sprintf("%s/%s", dir, "server.pem"), fmt.Sprintf("%s/%s", dir, "server.key"), mux)
	fmt.Printf("err:%v\n", err)
}

func getParentDirectory(directory string) string {
	return substr(directory, 0, strings.LastIndex(directory, string(os.PathSeparator)))
}

func substr(s string, pos, length int) string {
	runes := []rune(s)
	l := pos + length
	if l > len(runes) {
		l = len(runes)
	}
	return string(runes[pos:l])
}

这里可以看出来这里的主要的逻辑就是 http.ListenAndServeTLS。

ListenAndServeTLS

// ListenAndServeTLS acts identically to ListenAndServe, except that it
// expects HTTPS connections. Additionally, files containing a certificate and
// matching private key for the server must be provided. If the certificate
// is signed by a certificate authority, the certFile should be the concatenation
// of the server's certificate, any intermediates, and the CA's certificate.
func ListenAndServeTLS(addr, certFile, keyFile string, handler Handler) error {
    / 初始化一个Server
	server := &Server{Addr: addr, Handler: handler}
	return server.ListenAndServeTLS(certFile, keyFile)
}

这里初始化一个Server,然后调用ListenAndServeTLS

// ListenAndServeTLS listens on the TCP network address srv.Addr and
// then calls ServeTLS to handle requests on incoming TLS connections.
// Accepted connections are configured to enable TCP keep-alives.
//
// Filenames containing a certificate and matching private key for the
// server must be provided if neither the Server's TLSConfig.Certificates
// nor TLSConfig.GetCertificate are populated. If the certificate is
// signed by a certificate authority, the certFile should be the
// concatenation of the server's certificate, any intermediates, and
// the CA's certificate.
//
// If srv.Addr is blank, ":https" is used.
//
// ListenAndServeTLS always returns a non-nil error. After Shutdown or
// Close, the returned error is ErrServerClosed.
func (srv *Server) ListenAndServeTLS(certFile, keyFile string) error {
	if srv.shuttingDown() {
		return ErrServerClosed
	}
	addr := srv.Addr
	if addr == "" {
		addr = ":https"
	}
    
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}

	defer ln.Close()

	return srv.ServeTLS(ln, certFile, keyFile)
}

这里的主要方法都是比较正常通过Listen获取到一个连接。然后调用ServeTLS.

ServeTLS

// ServeTLS accepts incoming connections on the Listener l, creating a
// new service goroutine for each. The service goroutines perform TLS
// setup and then read requests, calling srv.Handler to reply to them.
//
// Files containing a certificate and matching private key for the
// server must be provided if neither the Server's
// TLSConfig.Certificates nor TLSConfig.GetCertificate are populated.
// If the certificate is signed by a certificate authority, the
// certFile should be the concatenation of the server's certificate,
// any intermediates, and the CA's certificate.
//
// ServeTLS always returns a non-nil error. After Shutdown or Close, the
// returned error is ErrServerClosed.
func (srv *Server) ServeTLS(l net.Listener, certFile, keyFile string) error {
	// Setup HTTP/2 before srv.Serve, to initialize srv.TLSConfig
	// before we clone it and create the TLS Listener.
	if err := srv.setupHTTP2_ServeTLS(); err != nil {
		return err
	}

	config := cloneTLSConfig(srv.TLSConfig)
	tlsListener := tls.NewListener(l, config)
	return srv.Serve(tlsListener)
}

这里主要是setupHTTP2_ServeTLS这个方法去初始化http2的serve.

setupHTTP2_ServeTLS

// setupHTTP2_ServeTLS conditionally configures HTTP/2 on
// srv and reports whether there was an error setting it up. If it is
// not configured for policy reasons, nil is returned.
func (srv *Server) setupHTTP2_ServeTLS() error {
	srv.nextProtoOnce.Do(srv.onceSetNextProtoDefaults)
	return srv.nextProtoErr
}
// onceSetNextProtoDefaults configures HTTP/2, if the user hasn't
// configured otherwise. (by setting srv.TLSNextProto non-nil)
// It must only be called via srv.nextProtoOnce (use srv.setupHTTP2_*).
func (srv *Server) onceSetNextProtoDefaults() {
	if omitBundledHTTP2 || strings.Contains(os.Getenv("GODEBUG"), "http2server=0") {
		return
	}
	// Enable HTTP/2 by default if the user hasn't otherwise
	// configured their TLSNextProto map.
	if srv.TLSNextProto == nil {
		conf := &http2Server{
			NewWriteScheduler: func() http2WriteScheduler { return http2NewPriorityWriteScheduler(nil) },
		}
		srv.nextProtoErr = http2ConfigureServer(srv, conf)
	}
}

这里是初始化了一个http2Server的结构体然后再传入到http2ConfigureServer。这个http2ConfigureServer是比较核心的理由http2处理连接具体的操作。

http2ConfigureServer

// ConfigureServer adds HTTP/2 support to a net/http Server.
//
// The configuration conf may be nil.
//
// ConfigureServer must be called before s begins serving.
func http2ConfigureServer(s *Server, conf *http2Server) error {
	// 真正处理请求的函数
	protoHandler := func(hs *Server, c *tls.Conn, h Handler) {
		if http2testHookOnConn != nil {
			http2testHookOnConn()
		}
		// The TLSNextProto interface predates contexts, so
		// the net/http package passes down its per-connection
		// base context via an exported but unadvertised
		// method on the Handler. This is for internal
		// net/http<=>http2 use only.
		var ctx context.Context
		type baseContexter interface {
			BaseContext() context.Context
		}
		if bc, ok := h.(baseContexter); ok {
			ctx = bc.BaseContext()
		}
		conf.ServeConn(c, &http2ServeConnOpts{
			Context:    ctx,
			Handler:    h,
			BaseConfig: hs,
		})
	}
	s.TLSNextProto[http2NextProtoTLS] = protoHandler
	return nil
}

这里的http2NextProtoTLS是一个常量是h2,代表的含义就是http2.然后注册在了TLSNextProto中这个后面用到的时候说。

Serve

// Serve accepts incoming connections on the Listener l, creating a
// new service goroutine for each. The service goroutines read requests and
// then call srv.Handler to reply to them.
//
// HTTP/2 support is only enabled if the Listener returns *tls.Conn
// connections and they were configured with "h2" in the TLS
// Config.NextProtos.
//
// Serve always returns a non-nil error and closes l.
// After Shutdown or Close, the returned error is ErrServerClosed.
func (srv *Server) Serve(l net.Listener) error {
	if fn := testHookServerServe; fn != nil {
		fn(srv, l) // call hook with unwrapped listener
	}

	origListener := l
	l = &onceCloseListener{Listener: l}
	defer l.Close()
    // 就是调用http2ConfigureServer方法 初始化http2Server
	if err := srv.setupHTTP2_Serve(); err != nil {
		return err
	}

	if !srv.trackListener(&l, true) {
		return ErrServerClosed
	}
	defer srv.trackListener(&l, false)

	baseCtx := context.Background()
	if srv.BaseContext != nil {
		baseCtx = srv.BaseContext(origListener)
		if baseCtx == nil {
			panic("BaseContext returned a nil context")
		}
	}

	var tempDelay time.Duration // how long to sleep on accept failure

	ctx := context.WithValue(baseCtx, ServerContextKey, srv)
	for {
		rw, err := l.Accept()
		if err != nil {
			select {
			case <-srv.getDoneChan():
				return ErrServerClosed
			default:
			}
			if ne, ok := err.(net.Error); ok && ne.Temporary() {
				if tempDelay == 0 {
					tempDelay = 5 * time.Millisecond
				} else {
					tempDelay *= 2
				}
				if max := 1 * time.Second; tempDelay > max {
					tempDelay = max
				}
				srv.logf("http: Accept error: %v; retrying in %v", err, tempDelay)
				time.Sleep(tempDelay)
				continue
			}
			return err
		}
		connCtx := ctx
		if cc := srv.ConnContext; cc != nil {
			connCtx = cc(connCtx, rw)
			if connCtx == nil {
				panic("ConnContext returned nil")
			}
		}
		tempDelay = 0
		c := srv.newConn(rw)
		c.setState(c.rwc, StateNew, runHooks) // before Serve can return
		go c.serve(connCtx)
	}
}

是的这个和正常的http的流程是一样的只是之前没有分析http是流程所以这里着重分析一下http2.0的流程也顺带看一下https的流程。上面就是正常的accept连接然后启动一个goroutine去处理请求。然后就是serve。

serve

// Serve a new connection.
func (c *conn) serve(ctx context.Context) {
	c.remoteAddr = c.rwc.RemoteAddr().String()
	ctx = context.WithValue(ctx, LocalAddrContextKey, c.rwc.LocalAddr())
	defer func() {
		if err := recover(); err != nil && err != ErrAbortHandler {
			const size = 64 << 10
			buf := make([]byte, size)
			buf = buf[:runtime.Stack(buf, false)]
			c.server.logf("http: panic serving %v: %v\n%s", c.remoteAddr, err, buf)
		}
		if !c.hijacked() {
			c.close()
			c.setState(c.rwc, StateClosed, runHooks)
		}
	}()
    // 判断是否是https接收的连接
	if tlsConn, ok := c.rwc.(*tls.Conn); ok {
	    // 设置读取超时
		if d := c.server.ReadTimeout; d != 0 {
			c.rwc.SetReadDeadline(time.Now().Add(d))
		}
		// 设置写入超时
		if d := c.server.WriteTimeout; d != 0 {
			c.rwc.SetWriteDeadline(time.Now().Add(d))
		}
		// 进行判断客户端的证书是否有效 进行tls/ssl层的握手
		if err := tlsConn.Handshake(); err != nil {
			// If the handshake failed due to the client not speaking
			// TLS, assume they're speaking plaintext HTTP and write a
			// 400 response on the TLS conn's underlying net.Conn.
			if re, ok := err.(tls.RecordHeaderError); ok && re.Conn != nil && tlsRecordHeaderLooksLikeHTTP(re.RecordHeader) {
				io.WriteString(re.Conn, "HTTP/1.0 400 Bad Request\r\n\r\nClient sent an HTTP request to an HTTPS server.\n")
				re.Conn.Close()
				return
			}
			c.server.logf("http: TLS handshake error from %s: %v", c.rwc.RemoteAddr(), err)
			return
		}
		// 到这里确定就是https的连接
		c.tlsState = new(tls.ConnectionState)
		*c.tlsState = tlsConn.ConnectionState()

	    // 判断client端的是不是http2.0如果不是http2.0
	    // 只是普通的https那么还是会走下面的http1.x的流程
		if proto := c.tlsState.NegotiatedProtocol; validNextProto(proto) {
		    // 是否有对应proto的handler
			if fn := c.server.TLSNextProto[proto]; fn != nil {
				h := initALPNRequest{ctx, tlsConn, serverHandler{c.server}}
				// Mark freshly created HTTP/2 as active and prevent any server state hooks
				// from being run on these connections. This prevents closeIdleConns from
				// closing such connections. See issue https://golang.org/issue/39776.
				c.setState(c.rwc, StateActive, skipHooks)
				fn(c.server, tlsConn, h)
			}
			return
		}
	}

	// HTTP/1.x from here on.
	// HTTP/1.x 的流程之前分析过这里不是看的重点因此忽略
}

这里可以看出来主要就是对于https握手的判断然后判断客户端是不是http2的协议然后初始化一个initALPNRequest的方法并传入到对应的方法中。接下来就是看一下对应的handler也就是

	protoHandler := func(hs *Server, c *tls.Conn, h Handler) {
		if http2testHookOnConn != nil {
			http2testHookOnConn()
		}
		// The TLSNextProto interface predates contexts, so
		// the net/http package passes down its per-connection
		// base context via an exported but unadvertised
		// method on the Handler. This is for internal
		// net/http<=>http2 use only.
		var ctx context.Context
		type baseContexter interface {
			BaseContext() context.Context
		}
		if bc, ok := h.(baseContexter); ok {
			ctx = bc.BaseContext()
		}
		// 这个是http2Server 
		conf.ServeConn(c, &http2ServeConnOpts{
			Context:    ctx,
			Handler:    h,
			BaseConfig: hs,
		})
	}

主要看一下http2Server中的ServeConn方法。

ServeConn

// ServeConn serves HTTP/2 requests on the provided connection and
// blocks until the connection is no longer readable.
//
// ServeConn starts speaking HTTP/2 assuming that c has not had any
// reads or writes. It writes its initial settings frame and expects
// to be able to read the preface and settings frame from the
// client. If c has a ConnectionState method like a *tls.Conn, the
// ConnectionState is used to verify the TLS ciphersuite and to set
// the Request.TLS field in Handlers.
//
// ServeConn does not support h2c by itself. Any h2c support must be
// implemented in terms of providing a suitably-behaving net.Conn.
//
// The opts parameter is optional. If nil, default values are used.
func (s *http2Server) ServeConn(c net.Conn, opts *http2ServeConnOpts) {
    // 获取http2的ctx
	baseCtx, cancel := http2serverConnBaseContext(c, opts)
	defer cancel()
    // 初始化http2serverConn
	sc := &http2serverConn{
		srv:                         s,
		hs:                          opts.baseConfig(),
		conn:                        c,
		baseCtx:                     baseCtx,
		remoteAddrStr:               c.RemoteAddr().String(),
		bw:                          http2newBufferedWriter(c),
		handler:                     opts.handler(),
		streams:                     make(map[uint32]*http2stream),
		readFrameCh:                 make(chan http2readFrameResult),
		wantWriteFrameCh:            make(chan http2FrameWriteRequest, 8),
		serveMsgCh:                  make(chan interface{}, 8),
		wroteFrameCh:                make(chan http2frameWriteResult, 1), // buffered; one send in writeFrameAsync
		bodyReadCh:                  make(chan http2bodyReadMsg),         // buffering doesn't matter either way
		doneServing:                 make(chan struct{}),
		clientMaxStreams:            math.MaxUint32, // Section 6.5.2: "Initially, there is no limit to this value"
		advMaxStreams:               s.maxConcurrentStreams(),
		initialStreamSendWindowSize: http2initialWindowSize,
		maxFrameSize:                http2initialMaxFrameSize,
		headerTableSize:             http2initialHeaderTableSize,
		serveG:                      http2newGoroutineLock(),
		pushEnabled:                 true,
	}

	s.state.registerConn(sc)
	defer s.state.unregisterConn(sc)

	// The net/http package sets the write deadline from the
	// http.Server.WriteTimeout during the TLS handshake, but then
	// passes the connection off to us with the deadline already set.
	// Write deadlines are set per stream in serverConn.newStream.
	// Disarm the net.Conn write deadline here.
	if sc.hs.WriteTimeout != 0 {
		sc.conn.SetWriteDeadline(time.Time{})
	}

	if s.NewWriteScheduler != nil {
		sc.writeSched = s.NewWriteScheduler()
	} else {
		sc.writeSched = http2NewRandomWriteScheduler()
	}

	// These start at the RFC-specified defaults. If there is a higher
	// configured value for inflow, that will be updated when we send a
	// WINDOW_UPDATE shortly after sending SETTINGS.
	// 设置流控
	sc.flow.add(http2initialWindowSize)
	sc.inflow.add(http2initialWindowSize)
	sc.hpackEncoder = hpack.NewEncoder(&sc.headerWriteBuf)
   
    // 设置frame
	fr := http2NewFramer(sc.bw, c)
	fr.ReadMetaHeaders = hpack.NewDecoder(http2initialHeaderTableSize, nil)
	fr.MaxHeaderListSize = sc.maxHeaderListSize()
	fr.SetMaxReadFrameSize(s.maxReadFrameSize())
	sc.framer = fr
    
    // 设置sc的serve
	sc.serve()
}

值得注意的是这里的writeSched就是默认的,也就是返回的是http2priorityWriteScheduler结构体。

// NewPriorityWriteScheduler constructs a WriteScheduler that schedules
// frames by following HTTP/2 priorities as described in RFC 7540 Section 5.3.
// If cfg is nil, default options are used.
func http2NewPriorityWriteScheduler(cfg *http2PriorityWriteSchedulerConfig) http2WriteScheduler {
	if cfg == nil {
		// For justification of these defaults, see:
		// https://docs.google.com/document/d/1oLhNg1skaWD4_DtaoCxdSRN5erEXrH-KnLrMwEpOtFY
		cfg = &http2PriorityWriteSchedulerConfig{
			MaxClosedNodesInTree:     10,
			MaxIdleNodesInTree:       10,
			ThrottleOutOfOrderWrites: false,
		}
	}

	ws := &http2priorityWriteScheduler{
		nodes:                make(map[uint32]*http2priorityNode),
		maxClosedNodesInTree: cfg.MaxClosedNodesInTree,
		maxIdleNodesInTree:   cfg.MaxIdleNodesInTree,
		enableWriteThrottle:  cfg.ThrottleOutOfOrderWrites,
	}
	ws.nodes[0] = &ws.root
	if cfg.ThrottleOutOfOrderWrites {
		ws.writeThrottleLimit = 1024
	} else {
		ws.writeThrottleLimit = math.MaxInt32
	}
	return ws
}

在调用的时候首先是初始化了一个http2serverConn.然后调用初始化流控也就是flow的参数的设置然后就是设置frame。然后在调用http2serverConn的serve。

func (sc *http2serverConn) serve() {
	sc.serveG.check()
	defer sc.notePanic()
	defer sc.conn.Close()
	defer sc.closeAllStreamsOnConnClose()
	defer sc.stopShutdownTimer()
	defer close(sc.doneServing) // unblocks handlers trying to send

	if http2VerboseLogs {
		sc.vlogf("http2: server connection from %v on %p", sc.conn.RemoteAddr(), sc.hs)
	}
    // 写入初始化的frame 设置初始化的参数
	sc.writeFrame(http2FrameWriteRequest{
		write: http2writeSettings{
			{http2SettingMaxFrameSize, sc.srv.maxReadFrameSize()},
			{http2SettingMaxConcurrentStreams, sc.advMaxStreams},
			{http2SettingMaxHeaderListSize, sc.maxHeaderListSize()},
			{http2SettingInitialWindowSize, uint32(sc.srv.initialStreamRecvWindowSize())},
		},
	})
	sc.unackedSettings++

	// Each connection starts with intialWindowSize inflow tokens.
	// If a higher value is configured, we add more tokens.
	if diff := sc.srv.initialConnRecvWindowSize() - http2initialWindowSize; diff > 0 {
		sc.sendWindowUpdate(nil, int(diff))
	}
    // 等待读取响应
	if err := sc.readPreface(); err != nil {
		sc.condlogf(err, "http2: server: error reading preface from client %v: %v", sc.conn.RemoteAddr(), err)
		return
	}
	// Now that we've got the preface, get us out of the
	// "StateNew" state. We can't go directly to idle, though.
	// Active means we read some data and anticipate a request. We'll
	// do another Active when we get a HEADERS frame.
	sc.setConnState(StateActive)
	sc.setConnState(StateIdle)

	if sc.srv.IdleTimeout != 0 {
		sc.idleTimer = time.AfterFunc(sc.srv.IdleTimeout, sc.onIdleTimer)
		defer sc.idleTimer.Stop()
	}
    // 开始异步读取frame
	go sc.readFrames() // closed by defer sc.conn.Close above
	
	settingsTimer := time.AfterFunc(http2firstSettingsTimeout, sc.onSettingsTimer)
	defer settingsTimer.Stop()

	loopNum := 0
	for {
		loopNum++
		select {
		// 有需要写入的数据
		case wr := <-sc.wantWriteFrameCh:
			if se, ok := wr.write.(http2StreamError); ok {
				sc.resetStream(se)
				break
			}
			sc.writeFrame(wr)
		// 有数据被写完了
		case res := <-sc.wroteFrameCh:
			sc.wroteFrame(res)
		// 读取到client的数据
		case res := <-sc.readFrameCh:
		    // 处理读取到的frame
			if !sc.processFrameFromReader(res) {
				return
			}
			res.readMore()
			if settingsTimer != nil {
				settingsTimer.Stop()
				settingsTimer = nil
			}
		case m := <-sc.bodyReadCh:
			sc.noteBodyRead(m.st, m.n)
		case msg := <-sc.serveMsgCh:
            // 判断一些异常的逻辑
			}
		}

		// If the peer is causing us to generate a lot of control frames,
		// but not reading them from us, assume they are trying to make us
		// run out of memory.
		if sc.queuedControlFrames > sc.srv.maxQueuedControlFrames() {
			sc.vlogf("http2: too many control frames in send queue, closing connection")
			return
		}

		// Start the shutdown timer after sending a GOAWAY. When sending GOAWAY
		// with no error code (graceful shutdown), don't start the timer until
		// all open streams have been completed.
		sentGoAway := sc.inGoAway && !sc.needToSendGoAway && !sc.writingFrame
		gracefulShutdownComplete := sc.goAwayCode == http2ErrCodeNo && sc.curOpenStreams() == 0
		if sentGoAway && sc.shutdownTimer == nil && (sc.goAwayCode != http2ErrCodeNo || gracefulShutdownComplete) {
			sc.shutDownIn(http2goAwayTimeout)
		}
	}
}

这里的逻辑主要就是首先写入初始化的frame这里面包括frame的大小限制stream的最大数量header的最大长度初始化的window的大小.然后写入到frame发送给client。
然后就是开始和client一样进行异步读取frame然后根据不同的frame去处理不同的逻辑。

readFrames

首先看一下异步读取frame也就是go sc.readFrames()这一段

// readFrames is the loop that reads incoming frames.
// It takes care to only read one frame at a time, blocking until the
// consumer is done with the frame.
// It's run on its own goroutine.
func (sc *http2serverConn) readFrames() {
	gate := make(http2gate)
	gateDone := gate.Done
	for {
	    // 读取frame
		f, err := sc.framer.ReadFrame()
		select {
		case sc.readFrameCh <- http2readFrameResult{f, err, gateDone}:
		case <-sc.doneServing:
			return
		}
		select {
		case <-gate:
		case <-sc.doneServing:
			return
		}
		if http2terminalReadFrameError(err) {
			return
		}
	}
}

这里的读取frame和client是一样的因为http2是支持推送的所以header头都是一样。然后读取到了之后写入到readFrameCh.这就是针对不同的frame去进行不同的操作。然后看一下就具体的写入逻辑

write frame

select {
		case wr := <-sc.wantWriteFrameCh:
			if se, ok := wr.write.(http2StreamError); ok {
				sc.resetStream(se)
				break
			}
			sc.writeFrame(wr)
		case res := <-sc.wroteFrameCh:
			sc.wroteFrame(res)
		case res := <-sc.readFrameCh:
			if !sc.processFrameFromReader(res) {
				return
			}
			res.readMore()
			if settingsTimer != nil {
				settingsTimer.Stop()
				settingsTimer = nil
			}

这里主要看一下 processFrameFromReader方法,或略err!=nil的情况这个其实就是调用processFrame方法。

func (sc *http2serverConn) processFrame(f http2Frame) error {
	sc.serveG.check()

	// First frame received must be SETTINGS.
	if !sc.sawFirstSettings {
		if _, ok := f.(*http2SettingsFrame); !ok {
			return http2ConnectionError(http2ErrCodeProtocol)
		}
		sc.sawFirstSettings = true
	}

	switch f := f.(type) {
	case *http2SettingsFrame: // 设置参数
		return sc.processSettings(f) 
	case *http2MetaHeadersFrame: // 返回数据和client
		return sc.processHeaders(f)
	case *http2WindowUpdateFrame:// window更新
		return sc.processWindowUpdate(f)
	case *http2PingFrame:
		return sc.processPing(f)
	case *http2DataFrame: // 处理client端推送来的数据
		return sc.processData(f)
	case *http2RSTStreamFrame:
		return sc.processResetStream(f)
	case *http2PriorityFrame:
		return sc.processPriority(f)
	case *http2GoAwayFrame:
		return sc.processGoAway(f)
	case *http2PushPromiseFrame:
		// A client cannot push. Thus, servers MUST treat the receipt of a PUSH_PROMISE
		// frame as a connection error (Section 5.4.1) of type PROTOCOL_ERROR.
		return http2ConnectionError(http2ErrCodeProtocol)
	default:
		sc.vlogf("http2: server ignoring frame: %v", f.Header())
		return nil
	}
}

这里类型比较多主要看一下http2MetaHeadersFrame这个这个是服务端给客户端推送数据。

func (sc *http2serverConn) processHeaders(f *http2MetaHeadersFrame) error {
	sc.serveG.check()
	id := f.StreamID
	if sc.inGoAway {
		// Ignore.
		return nil
	}
	// http://tools.ietf.org/html/rfc7540#section-5.1.1
	// Streams initiated by a client MUST use odd-numbered stream
	// identifiers. [...] An endpoint that receives an unexpected
	// stream identifier MUST respond with a connection error
	// (Section 5.4.1) of type PROTOCOL_ERROR.
	if id%2 != 1 {
		return http2ConnectionError(http2ErrCodeProtocol)
	}
 
	// [...] The identifier of a newly established stream MUST be
	// numerically greater than all streams that the initiating
	// endpoint has opened or reserved. [...]  An endpoint that
	// receives an unexpected stream identifier MUST respond with
	// a connection error (Section 5.4.1) of type PROTOCOL_ERROR.
	if id <= sc.maxClientStreamID {
		return http2ConnectionError(http2ErrCodeProtocol)
	}
	sc.maxClientStreamID = id

	if sc.idleTimer != nil {
		sc.idleTimer.Stop()
	}

	initialState := http2stateOpen
	if f.StreamEnded() {
		initialState = http2stateHalfClosedRemote
	}
	st := sc.newStream(id, 0, initialState)
    // 初始化request
	rw, req, err := sc.newWriterAndRequest(st, f)
	if err != nil {
		return err
	}
	st.reqTrailer = req.Trailer
	if st.reqTrailer != nil {
		st.trailer = make(Header)
	}
	st.body = req.Body.(*http2requestBody).pipe // may be nil
	st.declBodyBytes = req.ContentLength

	handler := sc.handler.ServeHTTP


	// The net/http package sets the read deadline from the
	// http.Server.ReadTimeout during the TLS handshake, but then
	// passes the connection off to us with the deadline already
	// set. Disarm it here after the request headers are read,
	// similar to how the http1 server works. Here it's
	// technically more like the http1 Server's ReadHeaderTimeout
	// (in Go 1.8), though. That's a more sane option anyway.
	if sc.hs.ReadTimeout != 0 {
		sc.conn.SetReadDeadline(time.Time{})
	}
    // 调用runHandler 也就是我们自己实现的handle.
	go sc.runHandler(rw, req, handler)
	return nil
}

因为http2.0 是兼容http1.x的所以这个request是和1.x是没有区别

func (sc *http2serverConn) newWriterAndRequest(st *http2stream, f *http2MetaHeadersFrame) (*http2responseWriter, *Request, error) {
	sc.serveG.check()
    // 实例化参数结构体
	rp := http2requestParam{
		method:    f.PseudoValue("method"),
		scheme:    f.PseudoValue("scheme"),
		authority: f.PseudoValue("authority"),
		path:      f.PseudoValue("path"),
	}
    // 删去校验代码

	rp.header = make(Header)
	for _, hf := range f.RegularFields() {
		rp.header.Add(sc.canonicalHeader(hf.Name), hf.Value)
	}
	if rp.authority == "" {
		rp.authority = rp.header.Get("Host")
	}

	rw, req, err := sc.newWriterAndRequestNoBody(st, rp)
	if err != nil {
		return nil, nil, err
	}
	if bodyOpen {
		if vv, ok := rp.header["Content-Length"]; ok {
			if cl, err := strconv.ParseUint(vv[0], 10, 63); err == nil {
				req.ContentLength = int64(cl)
			} else {
				req.ContentLength = 0
			}
		} else {
			req.ContentLength = -1
		}
		req.Body.(*http2requestBody).pipe = &http2pipe{
			b: &http2dataBuffer{expected: req.ContentLength},
		}
	}
	return rw, req, nil
}

再看一下newWriterAndRequestNoBody这个方法。

func (sc *http2serverConn) newWriterAndRequestNoBody(st *http2stream, rp http2requestParam) (*http2responseWriter, *Request, error) {
	sc.serveG.check()

	var tlsState *tls.ConnectionState // nil if not scheme https
	if rp.scheme == "https" {
		tlsState = sc.tlsState
	}

	needsContinue := rp.header.Get("Expect") == "100-continue"
	if needsContinue {
		rp.header.Del("Expect")
	}
	// Merge Cookie headers into one "; "-delimited value.
	if cookies := rp.header["Cookie"]; len(cookies) > 1 {
		rp.header.Set("Cookie", strings.Join(cookies, "; "))
	}

	// Setup Trailers
	var trailer Header
	for _, v := range rp.header["Trailer"] {
		for _, key := range strings.Split(v, ",") {
			key = CanonicalHeaderKey(textproto.TrimString(key))
			switch key {
			case "Transfer-Encoding", "Trailer", "Content-Length":
				// Bogus. (copy of http1 rules)
				// Ignore.
			default:
				if trailer == nil {
					trailer = make(Header)
				}
				trailer[key] = nil
			}
		}
	}
	delete(rp.header, "Trailer")

	var url_ *url.URL
	var requestURI string
	if rp.method == "CONNECT" {
		url_ = &url.URL{Host: rp.authority}
		requestURI = rp.authority // mimic HTTP/1 server behavior
	} else {
		var err error
		url_, err = url.ParseRequestURI(rp.path)
		if err != nil {
			return nil, nil, http2streamError(st.id, http2ErrCodeProtocol)
		}
		requestURI = rp.path
	}
    // 实例化http2requestBody
	body := &http2requestBody{
		conn:          sc,
		stream:        st,
		needsContinue: needsContinue,
	}
	// 实例化Request
	req := &Request{
		Method:     rp.method,
		URL:        url_,
		RemoteAddr: sc.remoteAddrStr,
		Header:     rp.header,
		RequestURI: requestURI,
		Proto:      "HTTP/2.0", // 走的http2.0的协议
		ProtoMajor: 2,
		ProtoMinor: 0,
		TLS:        tlsState,
		Host:       rp.authority,
		Body:       body,
		Trailer:    trailer,
	}
	req = req.WithContext(st.ctx)
    // 添加到rws中去
	rws := http2responseWriterStatePool.Get().(*http2responseWriterState)
	bwSave := rws.bw
	*rws = http2responseWriterState{} // zero all the fields
	rws.conn = sc
	rws.bw = bwSave
	rws.bw.Reset(http2chunkWriter{rws})
	rws.stream = st
	rws.req = req
	rws.body = body
    // 最后添加到http2responseWriter中
	rw := &http2responseWriter{rws: rws}
	return rw, req, nil
}

最后就是http2responseWriter这个结构体。
然后go sc.runHandler(rw, req, handler).

// Run on its own goroutine.
func (sc *http2serverConn) runHandler(rw *http2responseWriter, req *Request, handler func(ResponseWriter, *Request)) {
	didPanic := true
	defer func() {
		rw.rws.stream.cancelCtx()
		if didPanic {
			e := recover()
			sc.writeFrameFromHandler(http2FrameWriteRequest{
				write:  http2handlerPanicRST{rw.rws.stream.id},
				stream: rw.rws.stream,
			})
			// Same as net/http:
			if e != nil && e != ErrAbortHandler {
				const size = 64 << 10
				buf := make([]byte, size)
				buf = buf[:runtime.Stack(buf, false)]
				sc.logf("http2: panic serving %v: %v\n%s", sc.conn.RemoteAddr(), e, buf)
			}
			return
		}
		rw.handlerDone()
	}()
	handler(rw, req)
	didPanic = false
}

在调用完自己设置的handler后.调用handlerDone方法

func (w *http2responseWriter) handlerDone() {
	rws := w.rws
	dirty := rws.dirty
	rws.handlerDone = true
	w.Flush()
	w.rws = nil
	if !dirty {
		// Only recycle the pool if all prior Write calls to
		// the serverConn goroutine completed successfully. If
		// they returned earlier due to resets from the peer
		// there might still be write goroutines outstanding
		// from the serverConn referencing the rws memory. See
		// issue 20704.
		http2responseWriterStatePool.Put(rws)
	}
}

这里其实就是调用Flush将缓存的内容真正写入到了client中。