net/http: don't wrap request cancellation errors in timeouts

Based on Filippo Valsorda's https://golang.org/cl/24230

Fixes #16094

Change-Id: Ie39b0834e220f0a0f4fbfb3bbb271e70837718c3
Reviewed-on: https://go-review.googlesource.com/32478Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/client.go

@@ -218,7 +218,7 @@ func send(ireq *Request, rt RoundTripper, deadline time.Time) (*Response, error)
 	if !deadline.IsZero() {
 		forkReq()
 	}
-	stopTimer, wasCanceled := setRequestCancel(req, rt, deadline)
+	stopTimer, didTimeout := setRequestCancel(req, rt, deadline)
 
 	resp, err := rt.RoundTrip(req)
 	if err != nil {
@@ -238,9 +238,9 @@ func send(ireq *Request, rt RoundTripper, deadline time.Time) (*Response, error)
 	}
 	if !deadline.IsZero() {
 		resp.Body = &cancelTimerBody{
-			stop:           stopTimer,
-			rc:             resp.Body,
-			reqWasCanceled: wasCanceled,
+			stop:          stopTimer,
+			rc:            resp.Body,
+			reqDidTimeout: didTimeout,
 		}
 	}
 	return resp, nil
@@ -249,7 +249,7 @@ func send(ireq *Request, rt RoundTripper, deadline time.Time) (*Response, error)
 // setRequestCancel sets the Cancel field of req, if deadline is
 // non-zero. The RoundTripper's type is used to determine whether the legacy
 // CancelRequest behavior should be used.
-func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTimer func(), wasCanceled func() bool) {
+func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTimer func(), didTimeout func() bool) {
 	if deadline.IsZero() {
 		return nop, alwaysFalse
 	}
@@ -259,15 +259,6 @@ func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTi
 	cancel := make(chan struct{})
 	req.Cancel = cancel
 
-	wasCanceled = func() bool {
-		select {
-		case <-cancel:
-			return true
-		default:
-			return false
-		}
-	}
-
 	doCancel := func() {
 		// The new way:
 		close(cancel)
@@ -292,19 +283,22 @@ func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTi
 	stopTimer = func() { once.Do(func() { close(stopTimerCh) }) }
 
 	timer := time.NewTimer(time.Until(deadline))
+	var timedOut atomicBool
+
 	go func() {
 		select {
 		case <-initialReqCancel:
 			doCancel()
 			timer.Stop()
 		case <-timer.C:
+			timedOut.setTrue()
 			doCancel()
 		case <-stopTimerCh:
 			timer.Stop()
 		}
 	}()
 
-	return stopTimer, wasCanceled
+	return stopTimer, timedOut.isSet
 }
 
 // See 2 (end of page 4) http://www.ietf.org/rfc/rfc2617.txt
@@ -728,12 +722,12 @@ func (c *Client) Head(url string) (resp *Response, err error) {
 
 // cancelTimerBody is an io.ReadCloser that wraps rc with two features:
 // 1) on Read error or close, the stop func is called.
-// 2) On Read failure, if reqWasCanceled is true, the error is wrapped and
+// 2) On Read failure, if reqDidTimeout is true, the error is wrapped and
 //    marked as net.Error that hit its timeout.
 type cancelTimerBody struct {
-	stop           func() // stops the time.Timer waiting to cancel the request
-	rc             io.ReadCloser
-	reqWasCanceled func() bool
+	stop          func() // stops the time.Timer waiting to cancel the request
+	rc            io.ReadCloser
+	reqDidTimeout func() bool
 }
 
 func (b *cancelTimerBody) Read(p []byte) (n int, err error) {
@@ -745,7 +739,7 @@ func (b *cancelTimerBody) Read(p []byte) (n int, err error) {
 	if err == io.EOF {
 		return n, err
 	}
-	if b.reqWasCanceled() {
+	if b.reqDidTimeout() {
 		err = &httpError{
 			err:     err.Error() + " (Client.Timeout exceeded while reading body)",
 			timeout: true,

src/net/http/client_test.go

@@ -1185,10 +1185,12 @@ func TestClientTimeout_h1(t *testing.T) { testClientTimeout(t, h1Mode) }
 func TestClientTimeout_h2(t *testing.T) { testClientTimeout(t, h2Mode) }
 
 func testClientTimeout(t *testing.T, h2 bool) {
-	if testing.Short() {
-		t.Skip("skipping in short mode")
-	}
+	setParallel(t)
 	defer afterTest(t)
+	testDone := make(chan struct{})
+
+	const timeout = 100 * time.Millisecond
+
 	sawRoot := make(chan bool, 1)
 	sawSlow := make(chan bool, 1)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -1201,16 +1203,22 @@ func testClientTimeout(t *testing.T, h2 bool) {
 			w.Write([]byte("Hello"))
 			w.(Flusher).Flush()
 			sawSlow <- true
-			time.Sleep(2 * time.Second)
+			select {
+			case <-testDone:
+			case <-time.After(timeout * 10):
+			}
 			return
 		}
 	}))
 	defer cst.close()
-	const timeout = 500 * time.Millisecond
+	defer close(testDone)
 	cst.c.Timeout = timeout
 
 	res, err := cst.c.Get(cst.ts.URL)
 	if err != nil {
+		if strings.Contains(err.Error(), "Client.Timeout") {
+			t.Skip("host too slow to get fast resource in 100ms")
+		}
 		t.Fatal(err)
 	}
 
@@ -1260,11 +1268,9 @@ func TestClientTimeout_Headers_h2(t *testing.T) { testClientTimeout_Headers(t, h
 
 // Client.Timeout firing before getting to the body
 func testClientTimeout_Headers(t *testing.T, h2 bool) {
-	if testing.Short() {
-		t.Skip("skipping in short mode")
-	}
+	setParallel(t)
 	defer afterTest(t)
-	donec := make(chan bool)
+	donec := make(chan bool, 1)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		<-donec
 	}))
@@ -1278,9 +1284,10 @@ func testClientTimeout_Headers(t *testing.T, h2 bool) {
 	// doesn't know this, so synchronize explicitly.
 	defer func() { donec <- true }()
 
-	cst.c.Timeout = 500 * time.Millisecond
-	_, err := cst.c.Get(cst.ts.URL)
+	cst.c.Timeout = 5 * time.Millisecond
+	res, err := cst.c.Get(cst.ts.URL)
 	if err == nil {
+		res.Body.Close()
 		t.Fatal("got response from Get; expected error")
 	}
 	if _, ok := err.(*url.Error); !ok {
@@ -1298,6 +1305,36 @@ func testClientTimeout_Headers(t *testing.T, h2 bool) {
 	}
 }
 
+// Issue 16094: if Client.Timeout is set but not hit, a Timeout error shouldn't be
+// returned.
+func TestClientTimeoutCancel(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+
+	testDone := make(chan struct{})
+	ctx, cancel := context.WithCancel(context.Background())
+
+	cst := newClientServerTest(t, h1Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.(Flusher).Flush()
+		<-testDone
+	}))
+	defer cst.close()
+	defer close(testDone)
+
+	cst.c.Timeout = 1 * time.Hour
+	req, _ := NewRequest("GET", cst.ts.URL, nil)
+	req.Cancel = ctx.Done()
+	res, err := cst.c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cancel()
+	_, err = io.Copy(ioutil.Discard, res.Body)
+	if err != ExportErrRequestCanceled {
+		t.Fatal("error = %v; want errRequestCanceled")
+	}
+}
+
 func TestClientRedirectEatsBody_h1(t *testing.T) { testClientRedirectEatsBody(t, h1Mode) }
 func TestClientRedirectEatsBody_h2(t *testing.T) { testClientRedirectEatsBody(t, h2Mode) }
 func testClientRedirectEatsBody(t *testing.T, h2 bool) {
@@ -1317,10 +1354,10 @@ func testClientRedirectEatsBody(t *testing.T, h2 bool) {
 		t.Fatal(err)
 	}
 	_, err = ioutil.ReadAll(res.Body)
+	res.Body.Close()
 	if err != nil {
 		t.Fatal(err)
 	}
-	res.Body.Close()
 
 	var first string
 	select {