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 <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
2 files changed
tree: a322601a27c1c8670334e9285b747a487ca4b69b
  1. api/
  2. doc/
  3. lib/
  4. misc/
  5. src/
  6. test/
  7. .gitattributes
  8. .gitignore
  9. AUTHORS
  10. CONTRIBUTING.md
  11. CONTRIBUTORS
  12. favicon.ico
  13. LICENSE
  14. PATENTS
  15. README.md
  16. robots.txt
README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image

For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Please report issues here: https://golang.org/issue/new

Go is the work of hundreds of contributors. We appreciate your help!

To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html

Please note that we do not use pull requests.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.


Binary Distribution Notes

If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.

For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:

export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin

See https://golang.org/doc/install or doc/install.html for more details.