From 72970f7f52b1f8d14f10df40098175763a556ebe Mon Sep 17 00:00:00 2001 From: Brad Fitzpatrick Date: Mon, 6 Jul 2015 15:57:35 -0700 Subject: [PATCH] net/http/httputil: make ReverseProxy support Trailers Go's continuous build system depends on HTTP trailers for the buildlet interface. Andrew rewrote the makerelease tool to work in terms of Go's builder system (now at x/build/cmd/release), but it previously could only create GCE-based buildlets, which meant x/build/cmd/release couldn't build the release for Darwin. https://golang.org/cl/11901 added support for proxying buildlet connections via the coordinator, but that exposed the fact that httputil.ReverseProxy couldn't proxy Trailers. A fork of that code also wasn't possible because net/http needlessly deleted the "Trailer" response header in the Transport code. This mistake goes back to "release-branch.r56" and earlier but was never noticed because nobody ever uses Trailers, and servers via ResponseWriter never had the ability to even set trailers before this Go 1.5. Note that setting trailers requires pre-declaring (in the response header) which trailers you'll set later (after the response body). Because you could never set them, before this release you could also never proxy them. Change-Id: I2410a099921790dcd391675ae8610300efa19108 Reviewed-on: https://go-review.googlesource.com/11940 Reviewed-by: Andrew Gerrand Run-TryBot: Brad Fitzpatrick --- src/net/http/httputil/reverseproxy.go | 21 ++++++++++++++++++++- src/net/http/httputil/reverseproxy_test.go | 10 ++++++++++ 2 files changed, 30 insertions(+), 1 deletion(-) diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go index 5a0c1edfe1..3b7a184d93 100644 --- a/src/net/http/httputil/reverseproxy.go +++ b/src/net/http/httputil/reverseproxy.go @@ -194,7 +194,6 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) { rw.WriteHeader(http.StatusInternalServerError) return } - defer res.Body.Close() for _, h := range hopHeaders { res.Header.Del(h) @@ -202,8 +201,28 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) { copyHeader(rw.Header(), res.Header) + // The "Trailer" header isn't included in the Transport's response, + // at least for *http.Transport. Build it up from Trailer. + if len(res.Trailer) > 0 { + var trailerKeys []string + for k := range res.Trailer { + trailerKeys = append(trailerKeys, k) + } + rw.Header().Add("Trailer", strings.Join(trailerKeys, ", ")) + } + rw.WriteHeader(res.StatusCode) + if len(res.Trailer) > 0 { + // Force chunking if we saw a response trailer. + // This prevents net/http from calculating the length for short + // bodies and adding a Content-Length. + if fl, ok := rw.(http.Flusher); ok { + fl.Flush() + } + } p.copyResponse(rw, res.Body) + res.Body.Close() // close now, instead of defer, to populate res.Trailer + copyHeader(rw.Header(), res.Trailer) } func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader) { diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go index 54d2126aec..758f184962 100644 --- a/src/net/http/httputil/reverseproxy_test.go +++ b/src/net/http/httputil/reverseproxy_test.go @@ -12,6 +12,7 @@ import ( "net/http" "net/http/httptest" "net/url" + "reflect" "runtime" "strings" "testing" @@ -43,6 +44,7 @@ func TestReverseProxy(t *testing.T) { if g, e := r.Host, "some-name"; g != e { t.Errorf("backend got Host header %q, want %q", g, e) } + w.Header().Set("Trailer", "X-Trailer") w.Header().Set("X-Foo", "bar") w.Header().Set("Upgrade", "foo") w.Header().Set(fakeHopHeader, "foo") @@ -51,6 +53,7 @@ func TestReverseProxy(t *testing.T) { http.SetCookie(w, &http.Cookie{Name: "flavor", Value: "chocolateChip"}) w.WriteHeader(backendStatus) w.Write([]byte(backendResponse)) + w.Header().Set("X-Trailer", "trailer_value") })) defer backend.Close() backendURL, err := url.Parse(backend.URL) @@ -85,6 +88,9 @@ func TestReverseProxy(t *testing.T) { if g, e := len(res.Header["Set-Cookie"]), 1; g != e { t.Fatalf("got %d SetCookies, want %d", g, e) } + if g, e := res.Trailer, (http.Header{"X-Trailer": nil}); !reflect.DeepEqual(g, e) { + t.Errorf("before reading body, Trailer = %#v; want %#v", g, e) + } if cookie := res.Cookies()[0]; cookie.Name != "flavor" { t.Errorf("unexpected cookie %q", cookie.Name) } @@ -92,6 +98,10 @@ func TestReverseProxy(t *testing.T) { if g, e := string(bodyBytes), backendResponse; g != e { t.Errorf("got body %q; expected %q", g, e) } + if g, e := res.Trailer.Get("X-Trailer"), "trailer_value"; g != e { + t.Errorf("Trailer(X-Trailer) = %q ; want %q", g, e) + } + } func TestXForwardedFor(t *testing.T) { -- 2.50.0