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net/http: Transport.RoundTrip regression when retrying requests on Request.Body read error #18239

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bradfitz opened this issue Dec 8, 2016 · 4 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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@bradfitz
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bradfitz commented Dec 8, 2016

Bug report from Docker:

https://twitter.com/cpuguy83/status/806263794368397312 from moby/moby#29030

Repro from the change where I'm working on a fix:

func TestTransportBodyReadError(t *testing.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}  
  
        res, err := c.Get(ts.URL + "/ping")  
        if err != nil {  
                t.Fatal(err)  
        }  
        res.Body.Close()  
  
        r, w := io.Pipe()  
        errClose := errors.New("some error")  
        w.CloseWithError(errClose)  
        if _, err := c.Post(ts.URL+"/test", "", r); err != nil {  
                t.Logf("Got error: %v", err)  
        }  
}  

Go 1.7 always says "some error" as the error. In Go 1.8, we read from the request body, get an error, and then try to send the request again since we never wrote anything. But the first write ends up closing the request body (the pipe), and it can't be read the second time.

We need to do the same thing @tombergan and I did for http2 in golang/net@8dab929 and not retry a request once its Body has been messed with, unless it has a GetBody func that can be used to reset itself.

/cc @cpuguy83

@bradfitz bradfitz added the NeedsFix The path to resolution is known, but the work has not been done. label Dec 8, 2016
@bradfitz bradfitz added this to the Go1.8 milestone Dec 8, 2016
@bradfitz bradfitz self-assigned this Dec 8, 2016
@cpuguy83
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cpuguy83 commented Dec 8, 2016

Thanks for opening, was going to do this once the kids went to bed!

@gopherbot
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CL https://golang.org/cl/34134 mentions this issue.

@cpuguy83
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cpuguy83 commented Dec 8, 2016

Confirmed the changes in the CL fix our issue.

@cpuguy83
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cpuguy83 commented Dec 8, 2016

🎉

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