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transport.go
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transport.go
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// HTTP client implementation. See RFC 2616.
//
// This is the low-level Transport implementation of RoundTripper.
// The high-level interface is in client.go.
package http
import (
"bufio"
"compress/gzip"
"errors"
"fmt"
"github.com/MSOpenTech/azure-sdk-for-go/core/tls"
"io"
"log"
"net"
"net/url"
"os"
"strings"
"sync"
"time"
)
// DefaultTransport is the default implementation of Transport and is
// used by DefaultClient. It establishes network connections as needed
// and caches them for reuse by subsequent calls. It uses HTTP proxies
// as directed by the $HTTP_PROXY and $NO_PROXY (or $http_proxy and
// $no_proxy) environment variables.
var DefaultTransport RoundTripper = &Transport{
Proxy: ProxyFromEnvironment,
Dial: (&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
}).Dial,
TLSHandshakeTimeout: 10 * time.Second,
}
// DefaultMaxIdleConnsPerHost is the default value of Transport's
// MaxIdleConnsPerHost.
const DefaultMaxIdleConnsPerHost = 2
// Transport is an implementation of RoundTripper that supports http,
// https, and http proxies (for either http or https with CONNECT).
// Transport can also cache connections for future re-use.
type Transport struct {
idleMu sync.Mutex
idleConn map[connectMethodKey][]*persistConn
idleConnCh map[connectMethodKey]chan *persistConn
reqMu sync.Mutex
reqCanceler map[*Request]func()
altMu sync.RWMutex
altProto map[string]RoundTripper // nil or map of URI scheme => RoundTripper
// Proxy specifies a function to return a proxy for a given
// Request. If the function returns a non-nil error, the
// request is aborted with the provided error.
// If Proxy is nil or returns a nil *URL, no proxy is used.
Proxy func(*Request) (*url.URL, error)
// Dial specifies the dial function for creating TCP
// connections.
// If Dial is nil, net.Dial is used.
Dial func(network, addr string) (net.Conn, error)
// TLSClientConfig specifies the TLS configuration to use with
// tls.Client. If nil, the default configuration is used.
TLSClientConfig *tls.Config
// TLSHandshakeTimeout specifies the maximum amount of time waiting to
// wait for a TLS handshake. Zero means no timeout.
TLSHandshakeTimeout time.Duration
// DisableKeepAlives, if true, prevents re-use of TCP connections
// between different HTTP requests.
DisableKeepAlives bool
// DisableCompression, if true, prevents the Transport from
// requesting compression with an "Accept-Encoding: gzip"
// request header when the Request contains no existing
// Accept-Encoding value. If the Transport requests gzip on
// its own and gets a gzipped response, it's transparently
// decoded in the Response.Body. However, if the user
// explicitly requested gzip it is not automatically
// uncompressed.
DisableCompression bool
// MaxIdleConnsPerHost, if non-zero, controls the maximum idle
// (keep-alive) to keep per-host. If zero,
// DefaultMaxIdleConnsPerHost is used.
MaxIdleConnsPerHost int
// ResponseHeaderTimeout, if non-zero, specifies the amount of
// time to wait for a server's response headers after fully
// writing the request (including its body, if any). This
// time does not include the time to read the response body.
ResponseHeaderTimeout time.Duration
// TODO: tunable on global max cached connections
// TODO: tunable on timeout on cached connections
}
// ProxyFromEnvironment returns the URL of the proxy to use for a
// given request, as indicated by the environment variables
// $HTTP_PROXY and $NO_PROXY (or $http_proxy and $no_proxy).
// An error is returned if the proxy environment is invalid.
// A nil URL and nil error are returned if no proxy is defined in the
// environment, or a proxy should not be used for the given request.
//
// As a special case, if req.URL.Host is "localhost" (with or without
// a port number), then a nil URL and nil error will be returned.
func ProxyFromEnvironment(req *Request) (*url.URL, error) {
proxy := httpProxyEnv.Get()
if proxy == "" {
return nil, nil
}
if !useProxy(canonicalAddr(req.URL)) {
return nil, nil
}
proxyURL, err := url.Parse(proxy)
if err != nil || !strings.HasPrefix(proxyURL.Scheme, "http") {
// proxy was bogus. Try prepending "http://" to it and
// see if that parses correctly. If not, we fall
// through and complain about the original one.
if proxyURL, err := url.Parse("http://" + proxy); err == nil {
return proxyURL, nil
}
}
if err != nil {
return nil, fmt.Errorf("invalid proxy address %q: %v", proxy, err)
}
return proxyURL, nil
}
// ProxyURL returns a proxy function (for use in a Transport)
// that always returns the same URL.
func ProxyURL(fixedURL *url.URL) func(*Request) (*url.URL, error) {
return func(*Request) (*url.URL, error) {
return fixedURL, nil
}
}
// transportRequest is a wrapper around a *Request that adds
// optional extra headers to write.
type transportRequest struct {
*Request // original request, not to be mutated
extra Header // extra headers to write, or nil
}
func (tr *transportRequest) extraHeaders() Header {
if tr.extra == nil {
tr.extra = make(Header)
}
return tr.extra
}
// RoundTrip implements the RoundTripper interface.
//
// For higher-level HTTP client support (such as handling of cookies
// and redirects), see Get, Post, and the Client type.
func (t *Transport) RoundTrip(req *Request) (resp *Response, err error) {
if req.URL == nil {
req.closeBody()
return nil, errors.New("http: nil Request.URL")
}
if req.Header == nil {
req.closeBody()
return nil, errors.New("http: nil Request.Header")
}
if req.URL.Scheme != "http" && req.URL.Scheme != "https" {
t.altMu.RLock()
var rt RoundTripper
if t.altProto != nil {
rt = t.altProto[req.URL.Scheme]
}
t.altMu.RUnlock()
if rt == nil {
req.closeBody()
return nil, &badStringError{"unsupported protocol scheme", req.URL.Scheme}
}
return rt.RoundTrip(req)
}
if req.URL.Host == "" {
req.closeBody()
return nil, errors.New("http: no Host in request URL")
}
treq := &transportRequest{Request: req}
cm, err := t.connectMethodForRequest(treq)
if err != nil {
req.closeBody()
return nil, err
}
// Get the cached or newly-created connection to either the
// host (for http or https), the http proxy, or the http proxy
// pre-CONNECTed to https server. In any case, we'll be ready
// to send it requests.
pconn, err := t.getConn(req, cm)
if err != nil {
t.setReqCanceler(req, nil)
req.closeBody()
return nil, err
}
return pconn.roundTrip(treq)
}
// RegisterProtocol registers a new protocol with scheme.
// The Transport will pass requests using the given scheme to rt.
// It is rt's responsibility to simulate HTTP request semantics.
//
// RegisterProtocol can be used by other packages to provide
// implementations of protocol schemes like "ftp" or "file".
func (t *Transport) RegisterProtocol(scheme string, rt RoundTripper) {
if scheme == "http" || scheme == "https" {
panic("protocol " + scheme + " already registered")
}
t.altMu.Lock()
defer t.altMu.Unlock()
if t.altProto == nil {
t.altProto = make(map[string]RoundTripper)
}
if _, exists := t.altProto[scheme]; exists {
panic("protocol " + scheme + " already registered")
}
t.altProto[scheme] = rt
}
// CloseIdleConnections closes any connections which were previously
// connected from previous requests but are now sitting idle in
// a "keep-alive" state. It does not interrupt any connections currently
// in use.
func (t *Transport) CloseIdleConnections() {
t.idleMu.Lock()
m := t.idleConn
t.idleConn = nil
t.idleConnCh = nil
t.idleMu.Unlock()
for _, conns := range m {
for _, pconn := range conns {
pconn.close()
}
}
}
// CancelRequest cancels an in-flight request by closing its
// connection.
func (t *Transport) CancelRequest(req *Request) {
t.reqMu.Lock()
cancel := t.reqCanceler[req]
t.reqMu.Unlock()
if cancel != nil {
cancel()
}
}
//
// Private implementation past this point.
//
var (
httpProxyEnv = &envOnce{
names: []string{"HTTP_PROXY", "http_proxy"},
}
noProxyEnv = &envOnce{
names: []string{"NO_PROXY", "no_proxy"},
}
)
// envOnce looks up an environment variable (optionally by multiple
// names) once. It mitigates expensive lookups on some platforms
// (e.g. Windows).
type envOnce struct {
names []string
once sync.Once
val string
}
func (e *envOnce) Get() string {
e.once.Do(e.init)
return e.val
}
func (e *envOnce) init() {
for _, n := range e.names {
e.val = os.Getenv(n)
if e.val != "" {
return
}
}
}
// reset is used by tests
func (e *envOnce) reset() {
e.once = sync.Once{}
e.val = ""
}
func (t *Transport) connectMethodForRequest(treq *transportRequest) (cm connectMethod, err error) {
cm.targetScheme = treq.URL.Scheme
cm.targetAddr = canonicalAddr(treq.URL)
if t.Proxy != nil {
cm.proxyURL, err = t.Proxy(treq.Request)
}
return cm, nil
}
// proxyAuth returns the Proxy-Authorization header to set
// on requests, if applicable.
func (cm *connectMethod) proxyAuth() string {
if cm.proxyURL == nil {
return ""
}
if u := cm.proxyURL.User; u != nil {
username := u.Username()
password, _ := u.Password()
return "Basic " + basicAuth(username, password)
}
return ""
}
// putIdleConn adds pconn to the list of idle persistent connections awaiting
// a new request.
// If pconn is no longer needed or not in a good state, putIdleConn
// returns false.
func (t *Transport) putIdleConn(pconn *persistConn) bool {
if t.DisableKeepAlives || t.MaxIdleConnsPerHost < 0 {
pconn.close()
return false
}
if pconn.isBroken() {
return false
}
key := pconn.cacheKey
max := t.MaxIdleConnsPerHost
if max == 0 {
max = DefaultMaxIdleConnsPerHost
}
t.idleMu.Lock()
waitingDialer := t.idleConnCh[key]
select {
case waitingDialer <- pconn:
// We're done with this pconn and somebody else is
// currently waiting for a conn of this type (they're
// actively dialing, but this conn is ready
// first). Chrome calls this socket late binding. See
// https://insouciant.org/tech/connection-management-in-chromium/
t.idleMu.Unlock()
return true
default:
if waitingDialer != nil {
// They had populated this, but their dial won
// first, so we can clean up this map entry.
delete(t.idleConnCh, key)
}
}
if t.idleConn == nil {
t.idleConn = make(map[connectMethodKey][]*persistConn)
}
if len(t.idleConn[key]) >= max {
t.idleMu.Unlock()
pconn.close()
return false
}
for _, exist := range t.idleConn[key] {
if exist == pconn {
log.Fatalf("dup idle pconn %p in freelist", pconn)
}
}
t.idleConn[key] = append(t.idleConn[key], pconn)
t.idleMu.Unlock()
return true
}
// getIdleConnCh returns a channel to receive and return idle
// persistent connection for the given connectMethod.
// It may return nil, if persistent connections are not being used.
func (t *Transport) getIdleConnCh(cm connectMethod) chan *persistConn {
if t.DisableKeepAlives {
return nil
}
key := cm.key()
t.idleMu.Lock()
defer t.idleMu.Unlock()
if t.idleConnCh == nil {
t.idleConnCh = make(map[connectMethodKey]chan *persistConn)
}
ch, ok := t.idleConnCh[key]
if !ok {
ch = make(chan *persistConn)
t.idleConnCh[key] = ch
}
return ch
}
func (t *Transport) getIdleConn(cm connectMethod) (pconn *persistConn) {
key := cm.key()
t.idleMu.Lock()
defer t.idleMu.Unlock()
if t.idleConn == nil {
return nil
}
for {
pconns, ok := t.idleConn[key]
if !ok {
return nil
}
if len(pconns) == 1 {
pconn = pconns[0]
delete(t.idleConn, key)
} else {
// 2 or more cached connections; pop last
// TODO: queue?
pconn = pconns[len(pconns)-1]
t.idleConn[key] = pconns[:len(pconns)-1]
}
if !pconn.isBroken() {
return
}
}
}
func (t *Transport) setReqCanceler(r *Request, fn func()) {
t.reqMu.Lock()
defer t.reqMu.Unlock()
if t.reqCanceler == nil {
t.reqCanceler = make(map[*Request]func())
}
if fn != nil {
t.reqCanceler[r] = fn
} else {
delete(t.reqCanceler, r)
}
}
func (t *Transport) dial(network, addr string) (c net.Conn, err error) {
if t.Dial != nil {
return t.Dial(network, addr)
}
return net.Dial(network, addr)
}
// getConn dials and creates a new persistConn to the target as
// specified in the connectMethod. This includes doing a proxy CONNECT
// and/or setting up TLS. If this doesn't return an error, the persistConn
// is ready to write requests to.
func (t *Transport) getConn(req *Request, cm connectMethod) (*persistConn, error) {
if pc := t.getIdleConn(cm); pc != nil {
return pc, nil
}
type dialRes struct {
pc *persistConn
err error
}
dialc := make(chan dialRes)
handlePendingDial := func() {
if v := <-dialc; v.err == nil {
t.putIdleConn(v.pc)
}
}
cancelc := make(chan struct{})
t.setReqCanceler(req, func() { close(cancelc) })
go func() {
pc, err := t.dialConn(cm)
dialc <- dialRes{pc, err}
}()
idleConnCh := t.getIdleConnCh(cm)
select {
case v := <-dialc:
// Our dial finished.
return v.pc, v.err
case pc := <-idleConnCh:
// Another request finished first and its net.Conn
// became available before our dial. Or somebody
// else's dial that they didn't use.
// But our dial is still going, so give it away
// when it finishes:
go handlePendingDial()
return pc, nil
case <-cancelc:
go handlePendingDial()
return nil, errors.New("net/http: request canceled while waiting for connection")
}
}
func (t *Transport) dialConn(cm connectMethod) (*persistConn, error) {
conn, err := t.dial("tcp", cm.addr())
if err != nil {
if cm.proxyURL != nil {
err = fmt.Errorf("http: error connecting to proxy %s: %v", cm.proxyURL, err)
}
return nil, err
}
pa := cm.proxyAuth()
pconn := &persistConn{
t: t,
cacheKey: cm.key(),
conn: conn,
reqch: make(chan requestAndChan, 1),
writech: make(chan writeRequest, 1),
closech: make(chan struct{}),
writeErrCh: make(chan error, 1),
}
switch {
case cm.proxyURL == nil:
// Do nothing.
case cm.targetScheme == "http":
pconn.isProxy = true
if pa != "" {
pconn.mutateHeaderFunc = func(h Header) {
h.Set("Proxy-Authorization", pa)
}
}
case cm.targetScheme == "https":
connectReq := &Request{
Method: "CONNECT",
URL: &url.URL{Opaque: cm.targetAddr},
Host: cm.targetAddr,
Header: make(Header),
}
if pa != "" {
connectReq.Header.Set("Proxy-Authorization", pa)
}
connectReq.Write(conn)
// Read response.
// Okay to use and discard buffered reader here, because
// TLS server will not speak until spoken to.
br := bufio.NewReader(conn)
resp, err := ReadResponse(br, connectReq)
if err != nil {
conn.Close()
return nil, err
}
if resp.StatusCode != 200 {
f := strings.SplitN(resp.Status, " ", 2)
conn.Close()
return nil, errors.New(f[1])
}
}
if cm.targetScheme == "https" {
// Initiate TLS and check remote host name against certificate.
cfg := t.TLSClientConfig
if cfg == nil || cfg.ServerName == "" {
host := cm.tlsHost()
if cfg == nil {
cfg = &tls.Config{ServerName: host}
} else {
clone := *cfg // shallow clone
clone.ServerName = host
cfg = &clone
}
}
plainConn := conn
tlsConn := tls.Client(plainConn, cfg)
errc := make(chan error, 2)
var timer *time.Timer // for canceling TLS handshake
if d := t.TLSHandshakeTimeout; d != 0 {
timer = time.AfterFunc(d, func() {
errc <- tlsHandshakeTimeoutError{}
})
}
go func() {
err := tlsConn.Handshake()
if timer != nil {
timer.Stop()
}
errc <- err
}()
if err := <-errc; err != nil {
plainConn.Close()
return nil, err
}
if !cfg.InsecureSkipVerify {
if err := tlsConn.VerifyHostname(cfg.ServerName); err != nil {
plainConn.Close()
return nil, err
}
}
cs := tlsConn.ConnectionState()
pconn.tlsState = &cs
pconn.conn = tlsConn
}
pconn.br = bufio.NewReader(noteEOFReader{pconn.conn, &pconn.sawEOF})
pconn.bw = bufio.NewWriter(pconn.conn)
go pconn.readLoop()
go pconn.writeLoop()
return pconn, nil
}
// useProxy returns true if requests to addr should use a proxy,
// according to the NO_PROXY or no_proxy environment variable.
// addr is always a canonicalAddr with a host and port.
func useProxy(addr string) bool {
if len(addr) == 0 {
return true
}
host, _, err := net.SplitHostPort(addr)
if err != nil {
return false
}
if host == "localhost" {
return false
}
if ip := net.ParseIP(host); ip != nil {
if ip.IsLoopback() {
return false
}
}
no_proxy := noProxyEnv.Get()
if no_proxy == "*" {
return false
}
addr = strings.ToLower(strings.TrimSpace(addr))
if hasPort(addr) {
addr = addr[:strings.LastIndex(addr, ":")]
}
for _, p := range strings.Split(no_proxy, ",") {
p = strings.ToLower(strings.TrimSpace(p))
if len(p) == 0 {
continue
}
if hasPort(p) {
p = p[:strings.LastIndex(p, ":")]
}
if addr == p {
return false
}
if p[0] == '.' && (strings.HasSuffix(addr, p) || addr == p[1:]) {
// no_proxy ".foo.com" matches "bar.foo.com" or "foo.com"
return false
}
if p[0] != '.' && strings.HasSuffix(addr, p) && addr[len(addr)-len(p)-1] == '.' {
// no_proxy "foo.com" matches "bar.foo.com"
return false
}
}
return true
}
// connectMethod is the map key (in its String form) for keeping persistent
// TCP connections alive for subsequent HTTP requests.
//
// A connect method may be of the following types:
//
// Cache key form Description
// ----------------- -------------------------
// |http|foo.com http directly to server, no proxy
// |https|foo.com https directly to server, no proxy
// http://proxy.com|https|foo.com http to proxy, then CONNECT to foo.com
// http://proxy.com|http http to proxy, http to anywhere after that
//
// Note: no support to https to the proxy yet.
//
type connectMethod struct {
proxyURL *url.URL // nil for no proxy, else full proxy URL
targetScheme string // "http" or "https"
targetAddr string // Not used if proxy + http targetScheme (4th example in table)
}
func (cm *connectMethod) key() connectMethodKey {
proxyStr := ""
targetAddr := cm.targetAddr
if cm.proxyURL != nil {
proxyStr = cm.proxyURL.String()
if cm.targetScheme == "http" {
targetAddr = ""
}
}
return connectMethodKey{
proxy: proxyStr,
scheme: cm.targetScheme,
addr: targetAddr,
}
}
// addr returns the first hop "host:port" to which we need to TCP connect.
func (cm *connectMethod) addr() string {
if cm.proxyURL != nil {
return canonicalAddr(cm.proxyURL)
}
return cm.targetAddr
}
// tlsHost returns the host name to match against the peer's
// TLS certificate.
func (cm *connectMethod) tlsHost() string {
h := cm.targetAddr
if hasPort(h) {
h = h[:strings.LastIndex(h, ":")]
}
return h
}
// connectMethodKey is the map key version of connectMethod, with a
// stringified proxy URL (or the empty string) instead of a pointer to
// a URL.
type connectMethodKey struct {
proxy, scheme, addr string
}
func (k connectMethodKey) String() string {
// Only used by tests.
return fmt.Sprintf("%s|%s|%s", k.proxy, k.scheme, k.addr)
}
// persistConn wraps a connection, usually a persistent one
// (but may be used for non-keep-alive requests as well)
type persistConn struct {
t *Transport
cacheKey connectMethodKey
conn net.Conn
tlsState *tls.ConnectionState
br *bufio.Reader // from conn
sawEOF bool // whether we've seen EOF from conn; owned by readLoop
bw *bufio.Writer // to conn
reqch chan requestAndChan // written by roundTrip; read by readLoop
writech chan writeRequest // written by roundTrip; read by writeLoop
closech chan struct{} // closed when conn closed
isProxy bool
// writeErrCh passes the request write error (usually nil)
// from the writeLoop goroutine to the readLoop which passes
// it off to the res.Body reader, which then uses it to decide
// whether or not a connection can be reused. Issue 7569.
writeErrCh chan error
lk sync.Mutex // guards following fields
numExpectedResponses int
closed bool // whether conn has been closed
broken bool // an error has happened on this connection; marked broken so it's not reused.
// mutateHeaderFunc is an optional func to modify extra
// headers on each outbound request before it's written. (the
// original Request given to RoundTrip is not modified)
mutateHeaderFunc func(Header)
}
// isBroken reports whether this connection is in a known broken state.
func (pc *persistConn) isBroken() bool {
pc.lk.Lock()
b := pc.broken
pc.lk.Unlock()
return b
}
func (pc *persistConn) cancelRequest() {
pc.conn.Close()
}
var remoteSideClosedFunc func(error) bool // or nil to use default
func remoteSideClosed(err error) bool {
if err == io.EOF {
return true
}
if remoteSideClosedFunc != nil {
return remoteSideClosedFunc(err)
}
return false
}
func (pc *persistConn) readLoop() {
alive := true
for alive {
pb, err := pc.br.Peek(1)
pc.lk.Lock()
if pc.numExpectedResponses == 0 {
if !pc.closed {
pc.closeLocked()
if len(pb) > 0 {
log.Printf("Unsolicited response received on idle HTTP channel starting with %q; err=%v",
string(pb), err)
}
}
pc.lk.Unlock()
return
}
pc.lk.Unlock()
rc := <-pc.reqch
var resp *Response
if err == nil {
resp, err = ReadResponse(pc.br, rc.req)
if err == nil && resp.StatusCode == 100 {
// Skip any 100-continue for now.
// TODO(bradfitz): if rc.req had "Expect: 100-continue",
// actually block the request body write and signal the
// writeLoop now to begin sending it. (Issue 2184) For now we
// eat it, since we're never expecting one.
resp, err = ReadResponse(pc.br, rc.req)
}
}
if resp != nil {
resp.TLS = pc.tlsState
}
hasBody := resp != nil && rc.req.Method != "HEAD" && resp.ContentLength != 0
if err != nil {
pc.close()
} else {
if rc.addedGzip && hasBody && resp.Header.Get("Content-Encoding") == "gzip" {
resp.Header.Del("Content-Encoding")
resp.Header.Del("Content-Length")
resp.ContentLength = -1
resp.Body = &gzipReader{body: resp.Body}
}
resp.Body = &bodyEOFSignal{body: resp.Body}
}
if err != nil || resp.Close || rc.req.Close || resp.StatusCode <= 199 {
// Don't do keep-alive on error if either party requested a close
// or we get an unexpected informational (1xx) response.
// StatusCode 100 is already handled above.
alive = false
}
var waitForBodyRead chan bool
if hasBody {
waitForBodyRead = make(chan bool, 2)
resp.Body.(*bodyEOFSignal).earlyCloseFn = func() error {
// Sending false here sets alive to
// false and closes the connection
// below.
waitForBodyRead <- false
return nil
}
resp.Body.(*bodyEOFSignal).fn = func(err error) {
waitForBodyRead <- alive &&
err == nil &&
!pc.sawEOF &&
pc.wroteRequest() &&
pc.t.putIdleConn(pc)
}
}
if alive && !hasBody {
alive = !pc.sawEOF &&
pc.wroteRequest() &&
pc.t.putIdleConn(pc)
}
rc.ch <- responseAndError{resp, err}
// Wait for the just-returned response body to be fully consumed
// before we race and peek on the underlying bufio reader.
if waitForBodyRead != nil {
select {
case alive = <-waitForBodyRead:
case <-pc.closech:
alive = false
}
}
pc.t.setReqCanceler(rc.req, nil)
if !alive {
pc.close()
}
}
}
func (pc *persistConn) writeLoop() {
for {
select {
case wr := <-pc.writech:
if pc.isBroken() {
wr.ch <- errors.New("http: can't write HTTP request on broken connection")
continue
}
err := wr.req.Request.write(pc.bw, pc.isProxy, wr.req.extra)
if err == nil {
err = pc.bw.Flush()
}
if err != nil {
pc.markBroken()
wr.req.Request.closeBody()
}
pc.writeErrCh <- err // to the body reader, which might recycle us
wr.ch <- err // to the roundTrip function
case <-pc.closech:
return
}
}
}
// wroteRequest is a check before recycling a connection that the previous write
// (from writeLoop above) happened and was successful.
func (pc *persistConn) wroteRequest() bool {
select {
case err := <-pc.writeErrCh:
// Common case: the write happened well before the response, so
// avoid creating a timer.
return err == nil
default:
// Rare case: the request was written in writeLoop above but
// before it could send to pc.writeErrCh, the reader read it
// all, processed it, and called us here. In this case, give the
// write goroutine a bit of time to finish its send.
//
// Less rare case: We also get here in the legitimate case of
// Issue 7569, where the writer is still writing (or stalled),
// but the server has already replied. In this case, we don't
// want to wait too long, and we want to return false so this
// connection isn't re-used.
select {
case err := <-pc.writeErrCh:
return err == nil
case <-time.After(50 * time.Millisecond):
return false
}
}
}
type responseAndError struct {
res *Response
err error
}
type requestAndChan struct {
req *Request
ch chan responseAndError
// did the Transport (as opposed to the client code) add an
// Accept-Encoding gzip header? only if it we set it do
// we transparently decode the gzip.
addedGzip bool
}
// A writeRequest is sent by the readLoop's goroutine to the
// writeLoop's goroutine to write a request while the read loop
// concurrently waits on both the write response and the server's
// reply.
type writeRequest struct {
req *transportRequest
ch chan<- error
}
type httpError struct {
err string
timeout bool
}
func (e *httpError) Error() string { return e.err }
func (e *httpError) Timeout() bool { return e.timeout }
func (e *httpError) Temporary() bool { return true }
var errTimeout error = &httpError{err: "net/http: timeout awaiting response headers", timeout: true}
var errClosed error = &httpError{err: "net/http: transport closed before response was received"}
func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err error) {
pc.t.setReqCanceler(req.Request, pc.cancelRequest)
pc.lk.Lock()
pc.numExpectedResponses++
headerFn := pc.mutateHeaderFunc
pc.lk.Unlock()
if headerFn != nil {
headerFn(req.extraHeaders())
}
// Ask for a compressed version if the caller didn't set their
// own value for Accept-Encoding. We only attempted to
// uncompress the gzip stream if we were the layer that
// requested it.
requestedGzip := false
if !pc.t.DisableCompression && req.Header.Get("Accept-Encoding") == "" && req.Method != "HEAD" {
// Request gzip only, not deflate. Deflate is ambiguous and
// not as universally supported anyway.
// See: http://www.gzip.org/zlib/zlib_faq.html#faq38
//
// Note that we don't request this for HEAD requests,
// due to a bug in nginx:
// http://trac.nginx.org/nginx/ticket/358
// http://golang.org/issue/5522
requestedGzip = true
req.extraHeaders().Set("Accept-Encoding", "gzip")
}
// Write the request concurrently with waiting for a response,