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x/net/http2: Transport hangs forever if using a pipe that has not been written to yet as req.Body #17480

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luna-duclos opened this issue Oct 17, 2016 · 11 comments
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@luna-duclos luna-duclos commented Oct 17, 2016

### What version of Go are you using (go version)?
Go 1.7.1

### What operating system and processor architecture are you using (go env)?

set GOARCH=amd64                                                                                                                                                
set GOBIN=                                                                                                                                                      
set GOEXE=.exe                                                                                                                                                  
set GOHOSTARCH=amd64                                                                                                                                            
set GOHOSTOS=windows                                                                                                                                            
set GOOS=windows                                                                                                                                                
set GOPATH=D:\src\psg\server;D:\src\psg\server\vendor                                                                                                           
set GORACE=                                                                                                                                                     
set GOROOT=C:\apps\Go                                                                                                                                           
set GOTOOLDIR=C:\apps\Go\pkg\tool\windows_amd64                                                                                                                 
set CC=gcc                                                                                                                                                      
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\lunad\AppData\Local\Temp\go-build906126950=/tmp/go-build -gno-record-gcc-switches  
set CXX=g++                                                                                                                                                     
set CGO_ENABLED=1                                                                                                                                               

### What did you do?
If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

I ran the following program:

package main

import (
    "crypto/rand"
    "io"
    "log"
    "net/http"
    "runtime/debug"
    "time"

    "golang.org/x/net/http2"
)

func main() {
    // set a 10 second timer for success
    go func() {
        timer := time.NewTimer(10 * time.Second)
        <-timer.C
        debug.SetTraceback("all")
        panic("10 second test period expired")
    }()

    transport := &http2.Transport{}
    c := &http.Client{Transport: transport}

    // Get a set of pipes, we'll use these to send data to the server
    pipeReader, pipeWriter := io.Pipe()

    // Initialize the request
    req, err := http.NewRequest("PUT", "https://http2.golang.org/bidirectional-stream", pipeReader)
    if err != nil {
        pipeWriter.Close()
        log.Fatalf("Error while initializing http request: %v", err)
    }

    // Set the body of the request to the reader end of our pipe, and initiate the request.
    req.Body = pipeReader
    resp, err := c.Do(req)
    if err != nil {
        pipeWriter.Close()
        log.Fatalf("Error during http call: %v", err)
    }

    // Check that we actually got a 200 OK, if not: error out
    if resp.StatusCode != http.StatusOK {
        resp.Body.Close()
        pipeWriter.Close()
        log.Fatalf("http call got non-200 status code %d", resp.StatusCode)
    }

    // Use a 10 byte buffer
    buffer := make([]byte, 10)

    // Read some data
    dataLen, err := resp.Body.Read(buffer)
    if err != nil {
        log.Fatalf("Error while reading data: %v", err)
    }

    log.Printf("Got data: %+v", buffer[:dataLen])

    // Reply
    if _, err := rand.Read(buffer); err != nil {
        log.Fatalf("Error while reading random data: %v", err)
    }

    if _, err := pipeWriter.Write(buffer); err != nil {
        log.Fatalf("Error while writing data: %v", err)
    }
}

### What did you expect to see?
I expected to see a bidirectional http-2 stream, with the server talking first, and the client then replying to the server.

### What did you see instead?
The program hangs within http2/transport.go, in the bodyAndLength function, due to that function doing a Read(), which ofcourse hangs.

@luna-duclos luna-duclos changed the title x/net/http2: Client tries a Read() to determine body length x/net/http2: Transport hangs forever if using a pipe that has not been written to yet as req.Body Oct 17, 2016
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@bradfitz bradfitz commented Oct 17, 2016

Workaround: set your Request.ContentLength to -1 after http.NewRequest, before Client.Do.

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@luna-duclos luna-duclos commented Oct 17, 2016

The workaround works :) Thank you

@bradfitz bradfitz self-assigned this Oct 17, 2016
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@bradfitz bradfitz commented Oct 17, 2016

The larger issue is to remind myself why we need to distinguish between explicitly-zero and unset-so-zero in Request.ContentLength. Presumably there was a reason. Or maybe there was only a reason for HTTP/1 and it's less important for HTTP/2.

In any case, investigate.

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@gopherbot gopherbot commented Oct 18, 2016

CL https://golang.org/cl/31326 mentions this issue.

gopherbot pushed a commit to golang/net that referenced this issue Oct 18, 2016
…Length

Updates golang/go#17480 (fixes after vendor to std)
Updates golang/go#17071 (a better fix than the original one)

Change-Id: Ibb49d2cb825e28518e688b5c3e0952956a305050
Reviewed-on: https://go-review.googlesource.com/31326
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
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@gopherbot gopherbot commented Oct 18, 2016

CL https://golang.org/cl/31361 mentions this issue.

gopherbot pushed a commit to golang/net that referenced this issue Oct 18, 2016
…rt to determine ContentLength

Updates golang/go#17480 (fixes after vendor to std)
Updates golang/go#17071 (a better fix than the original one)

Change-Id: Ibb49d2cb825e28518e688b5c3e0952956a305050
Reviewed-on: https://go-review.googlesource.com/31326
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Reviewed-on: https://go-review.googlesource.com/31361
Run-TryBot: Chris Broadfoot <cbro@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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@gopherbot gopherbot commented Oct 18, 2016

CL https://golang.org/cl/31432 mentions this issue.

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@gopherbot gopherbot commented Oct 18, 2016

CL https://golang.org/cl/31434 mentions this issue.

gopherbot pushed a commit that referenced this issue Oct 18, 2016
The way to send an explicitly-zero Content-Length is to set a nil Body.

Fix this test to do that, rather than relying on type sniffing.

Updates #17480
Updates #17071

Change-Id: I6a38e20f17013c88ec4ea69d73c507e4ed886947
Reviewed-on: https://go-review.googlesource.com/31434
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
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@gopherbot gopherbot commented Oct 18, 2016

CL https://golang.org/cl/31437 mentions this issue.

gopherbot pushed a commit that referenced this issue Oct 18, 2016
…0 Body more reliably

The way to send an explicitly-zero Content-Length is to set a nil Body.

Fix this test to do that, rather than relying on type sniffing.

Updates #17480
Updates #17071

Change-Id: I6a38e20f17013c88ec4ea69d73c507e4ed886947
Reviewed-on: https://go-review.googlesource.com/31434
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Reviewed-on: https://go-review.googlesource.com/31437
Run-TryBot: Chris Broadfoot <cbro@golang.org>
gopherbot pushed a commit that referenced this issue Oct 19, 2016
Updates bundled http2 for x/net/http2 git rev d4c55e66 for:

[release-branch.go1.7] http2: never Read from Request.Body in Transport
to determine ContentLength
https://golang.org/cl/31361

Updates #17480
Updates #17071

Change-Id: I2231adaed3cb5b368927a9654dcf7e69a8b664b6
Reviewed-on: https://go-review.googlesource.com/31432
Run-TryBot: Chris Broadfoot <cbro@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
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@gopherbot gopherbot commented Oct 19, 2016

CL https://golang.org/cl/31445 mentions this issue.

gopherbot pushed a commit that referenced this issue Oct 19, 2016
… Transport

This CL makes NewRequest set Body nil for known-zero bodies, and makes
the http1 Transport not peek-Read a byte to determine whether there's
a body.

Background:

Many fields of the Request struct have different meanings for whether
they're outgoing (via the Transport) or incoming (via the Server).

For outgoing requests, ContentLength and Body are documented as:

	// Body is the request's body.
	//
	// For client requests a nil body means the request has no
	// body, such as a GET request. The HTTP Client's Transport
	// is responsible for calling the Close method.
	Body io.ReadCloser

	// ContentLength records the length of the associated content.
	// The value -1 indicates that the length is unknown.
	// Values >= 0 indicate that the given number of bytes may
	// be read from Body.
	// For client requests, a value of 0 with a non-nil Body is
	// also treated as unknown.
	ContentLength int64

Because of the ambiguity of what ContentLength==0 means, the http1 and
http2 Transports previously Read the first byte of a non-nil Body when
the ContentLength was 0 to determine whether there was an actual body
(with a non-zero length) and ContentLength just wasn't populated, or
it was actually empty.

That byte-sniff has been problematic and gross (see #17480, #17071)
and was removed for http2 in a previous commit.

That means, however, that users doing:

    req, _ := http.NewRequest("POST", url, strings.NewReader(""))

... would not send a Content-Length header in their http2 request,
because the size of the reader (even though it was known, being one of
the three common recognized types from NewRequest) was zero, and so
the HTTP Transport thought it was simply unset.

To signal explicitly-zero vs unset-zero, this CL changes NewRequest to
signal explicitly-zero by setting the Body to nil, instead of the
strings.NewReader("") or other zero-byte reader.

This CL also removes the byte sniff from the http1 Transport, like
https://golang.org/cl/31326 did for http2.

Updates #17480
Updates #17071

Change-Id: I329f02f124659bf7d8bc01e2c9951ebdd236b52a
Reviewed-on: https://go-review.googlesource.com/31445
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
@quentinmit quentinmit added the NeedsFix label Oct 21, 2016
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@gopherbot gopherbot commented Oct 21, 2016

CL https://golang.org/cl/31737 mentions this issue.

@gopherbot gopherbot closed this in a50fbcd Oct 21, 2016
ceseo added a commit to powertechpreview/go that referenced this issue Dec 1, 2016
…0 Body more reliably

The way to send an explicitly-zero Content-Length is to set a nil Body.

Fix this test to do that, rather than relying on type sniffing.

Updates golang#17480
Updates golang#17071

Change-Id: I6a38e20f17013c88ec4ea69d73c507e4ed886947
Reviewed-on: https://go-review.googlesource.com/31434
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Reviewed-on: https://go-review.googlesource.com/31437
Run-TryBot: Chris Broadfoot <cbro@golang.org>
ceseo added a commit to powertechpreview/go that referenced this issue Dec 1, 2016
Updates bundled http2 for x/net/http2 git rev d4c55e66 for:

[release-branch.go1.7] http2: never Read from Request.Body in Transport
to determine ContentLength
https://golang.org/cl/31361

Updates golang#17480
Updates golang#17071

Change-Id: I2231adaed3cb5b368927a9654dcf7e69a8b664b6
Reviewed-on: https://go-review.googlesource.com/31432
Run-TryBot: Chris Broadfoot <cbro@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
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@gopherbot gopherbot commented Dec 22, 2016

CL https://golang.org/cl/34668 mentions this issue.

gopherbot pushed a commit that referenced this issue Dec 22, 2016
In Go 1.8, we'd removed the Transport's Request.Body
one-byte-Read-sniffing to disambiguate between non-nil Request.Body
with a ContentLength of 0 or -1. Previously, we tried to see whether a
ContentLength of 0 meant actually zero, or just an unset by reading a
single byte of the Request.Body and then stitching any read byte back
together with the original Request.Body.

That historically has caused many problems due to either data races,
blocking forever (#17480), or losing bytes (#17071). Thus, we removed
it in both HTTP/1 and HTTP/2 in Go 1.8. Unfortunately, during the Go
1.8 beta, we've found that a few people have gotten bitten by the
behavior change on requests with methods typically not containing
request bodies (e.g. GET, HEAD, DELETE). The most popular example is
the aws-go SDK, which always set http.Request.Body to a non-nil value,
even on such request methods. That was causing Go 1.8 to send such
requests with Transfer-Encoding chunked bodies, with zero bytes,
confusing popular servers (including but limited to AWS).

This CL partially reverts the no-byte-sniffing behavior and restores
it only for GET/HEAD/DELETE/etc requests, and only when there's no
Transfer-Encoding set, and the Content-Length is 0 or -1.

Updates #18257 (aws-go) bug
And also private bug reports about non-AWS issues.

Updates #18407 also, but haven't yet audited things enough to declare
it fixed.

Change-Id: Ie5284d3e067c181839b31faf637eee56e5738a6a
Reviewed-on: https://go-review.googlesource.com/34668
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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