mirror of https://github.com/golang/go.git
ebe91d1105
A response to a HEAD request is supposed to look the same as a response to a GET request, just without a body. HEAD requests are incredibly rare in the wild. The Go net/http package has so far treated HEAD requests specially: a Write on our default ResponseWriter returned ErrBodyNotAllowed, telling handlers that something was wrong. This was to optimize the fast path for HEAD requests, but: 1) because HEAD requests are incredibly rare, they're not worth having a fast path for. 2) Letting the http.Handler handle but do nop Writes is still very fast. 3) this forces ugly error handling into the application. e.g. https://code.google.com/p/go/source/detail?r=6f596be7a31e and related. 4) The net/http package nowadays does Content-Type sniffing, but you don't get that for HEAD. 5) The net/http package nowadays does Content-Length counting for small (few KB) responses, but not for HEAD. 6) ErrBodyNotAllowed was useless. By the time you received it, you had probably already done all your heavy computation and I/O to calculate what to write. So, this change makes HEAD requests like GET requests. We now count content-length and sniff content-type for HEAD requests. If you Write, it doesn't return an error. If you want a fast-path in your code for HEAD, you have to do it early and set all the response headers yourself. Just like before. If you choose not to Write in HEAD requests, be sure to set Content-Length if you know it. We won't write "Content-Length: 0" because you might've just chosen to not write (or you don't know your Content-Length in advance). Fixes #5454 R=golang-dev, dsymonds CC=golang-dev https://golang.org/cl/12583043 |
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README
This is the source code repository for the Go programming language.
For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install.html in your web browser.
After installing Go, you can view a nicely formatted
doc/install.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install.html.
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 README). 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.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 doc/install.html for more details.