net/http: don't retry Transport requests if they have a body

This rolls back https://golang.org/cl/27117 partly, softening it so it
only retries POST/PUT/DELETE etc requests where there's no Body (nil
or NoBody). This is a little useless, since most idempotent requests
have a body (except maybe DELETE), but it's late in the Go 1.8 release
cycle and I want to do the proper fix.

The proper fix will look like what we did for http2 and only retrying
the request if Request.GetBody is defined, and then creating a new request
for the next attempt. See https://golang.org/cl/33971 for the http2 fix.

Updates #15723
Fixes #18239
Updates #18241

Change-Id: I6ebaa1fd9b19b5ccb23c8d9e7b3b236e71cf57f3
Reviewed-on: https://go-review.googlesource.com/34134
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Tom Bergan <[email protected]>

doc/go1.8.html

@@ -1311,7 +1311,8 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
 
       <li><!-- CL 27117 -->
         The <code>Transport</code> will now retry non-idempotent
-        requests if no bytes were written before a network failure.
+        requests if no bytes were written before a network failure
+        and the request has no body.
       </li>
 
       <li><!-- CL 32481 -->

src/net/http/client_test.go

@@ -26,6 +26,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 )
@@ -1738,3 +1739,76 @@ func TestClientRedirectTypes(t *testing.T) {
 		res.Body.Close()
 	}
 }
+
+// issue18239Body is an io.ReadCloser for TestTransportBodyReadError.
+// Its Read returns readErr and increments *readCalls atomically.
+// Its Close returns nil and increments *closeCalls atomically.
+type issue18239Body struct {
+	readCalls  *int32
+	closeCalls *int32
+	readErr    error
+}
+
+func (b issue18239Body) Read([]byte) (int, error) {
+	atomic.AddInt32(b.readCalls, 1)
+	return 0, b.readErr
+}
+
+func (b issue18239Body) Close() error {
+	atomic.AddInt32(b.closeCalls, 1)
+	return nil
+}
+
+// Issue 18239: make sure the Transport doesn't retry requests with bodies.
+// (Especially if Request.GetBody is not defined.)
+func TestTransportBodyReadError(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.URL.Path == "/ping" {
+			return
+		}
+		buf := make([]byte, 1)
+		n, err := r.Body.Read(buf)
+		w.Header().Set("X-Body-Read", fmt.Sprintf("%v, %v", n, err))
+	}))
+	defer ts.Close()
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	// Do one initial successful request to create an idle TCP connection
+	// for the subsequent request to reuse. (The Transport only retries
+	// requests on reused connections.)
+	res, err := c.Get(ts.URL + "/ping")
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	var readCallsAtomic int32
+	var closeCallsAtomic int32 // atomic
+	someErr := errors.New("some body read error")
+	body := issue18239Body{&readCallsAtomic, &closeCallsAtomic, someErr}
+
+	req, err := NewRequest("POST", ts.URL, body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = tr.RoundTrip(req)
+	if err != someErr {
+		t.Errorf("Got error: %v; want Request.Body read error: %v", err, someErr)
+	}
+
+	// And verify that our Body wasn't used multiple times, which
+	// would indicate retries. (as it buggily was during part of
+	// Go 1.8's dev cycle)
+	readCalls := atomic.LoadInt32(&readCallsAtomic)
+	closeCalls := atomic.LoadInt32(&closeCallsAtomic)
+	if readCalls != 1 {
+		t.Errorf("read calls = %d; want 1", readCalls)
+	}
+	if closeCalls != 1 {
+		t.Errorf("close calls = %d; want 1", closeCalls)
+	}
+}

src/net/http/transport.go

@@ -1384,7 +1384,7 @@ func (pc *persistConn) closeConnIfStillIdle() {
 //
 // The startBytesWritten value should be the value of pc.nwrite before the roundTrip
 // started writing the request.
-func (pc *persistConn) mapRoundTripErrorFromReadLoop(startBytesWritten int64, err error) (out error) {
+func (pc *persistConn) mapRoundTripErrorFromReadLoop(req *Request, startBytesWritten int64, err error) (out error) {
 	if err == nil {
 		return nil
 	}
@@ -1399,7 +1399,7 @@ func (pc *persistConn) mapRoundTripErrorFromReadLoop(startBytesWritten int64, er
 	}
 	if pc.isBroken() {
 		<-pc.writeLoopDone
-		if pc.nwrite == startBytesWritten {
+		if pc.nwrite == startBytesWritten && req.outgoingLength() == 0 {
 			return nothingWrittenError{err}
 		}
 	}
@@ -1410,7 +1410,7 @@ func (pc *persistConn) mapRoundTripErrorFromReadLoop(startBytesWritten int64, er
 // up to Transport.RoundTrip method when persistConn.roundTrip sees
 // its pc.closech channel close, indicating the persistConn is dead.
 // (after closech is closed, pc.closed is valid).
-func (pc *persistConn) mapRoundTripErrorAfterClosed(startBytesWritten int64) error {
+func (pc *persistConn) mapRoundTripErrorAfterClosed(req *Request, startBytesWritten int64) error {
 	if err := pc.canceled(); err != nil {
 		return err
 	}
@@ -1428,7 +1428,7 @@ func (pc *persistConn) mapRoundTripErrorAfterClosed(startBytesWritten int64) err
 	// see if we actually managed to write anything. If not, we
 	// can retry the request.
 	<-pc.writeLoopDone
-	if pc.nwrite == startBytesWritten {
+	if pc.nwrite == startBytesWritten && req.outgoingLength() == 0 {
 		return nothingWrittenError{err}
 	}
 
@@ -1710,7 +1710,7 @@ func (pc *persistConn) writeLoop() {
 			}
 			if err != nil {
 				wr.req.Request.closeBody()
-				if pc.nwrite == startBytesWritten {
+				if pc.nwrite == startBytesWritten && wr.req.outgoingLength() == 0 {
 					err = nothingWrittenError{err}
 				}
 			}
@@ -1911,14 +1911,14 @@ WaitResponse:
 				respHeaderTimer = timer.C
 			}
 		case <-pc.closech:
-			re = responseAndError{err: pc.mapRoundTripErrorAfterClosed(startBytesWritten)}
+			re = responseAndError{err: pc.mapRoundTripErrorAfterClosed(req.Request, startBytesWritten)}
 			break WaitResponse
 		case <-respHeaderTimer:
 			pc.close(errTimeout)
 			re = responseAndError{err: errTimeout}
 			break WaitResponse
 		case re = <-resc:
-			re.err = pc.mapRoundTripErrorFromReadLoop(startBytesWritten, re.err)
+			re.err = pc.mapRoundTripErrorFromReadLoop(req.Request, startBytesWritten, re.err)
 			break WaitResponse
 		case <-cancelChan:
 			pc.t.CancelRequest(req.Request)