HEAD responses contain body

Eric Wong normalperson at yhbt.net
Thu Jun 13 19:21:45 UTC 2013


Jonathan Rudenberg <jonathan at titanous.com> wrote:
> On Jun 13, 2013, at 2:22 PM, Eric Wong <normalperson at yhbt.net> wrote:
> > Jonathan Rudenberg <jonathan at titanous.com> wrote:
> >> RFC 2616 section 9.4[1] states:
> >> 
> >>> The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response.
> >> 
> >> A HEAD request against this simple Rack app running on unicorn-4.6.2:
> >> 
> >>    require 'rack'
> >> 
> > 
> > +     use Rack::Head
> > 
> >>    run lambda { |env| [200, {}, []] }
> > 
> > The Rack::Head middleware should be used to correctly strip HEAD
> > responses of their bodies (frameworks such as Rails/Sinatra should
> > already add Rack::Head to the middleware stack for you)
> 
> This does not change the result, as the Rack::Head implementation looks like this:
> 
>     def call(env)
>       status, headers, body = @app.call(env)
> 
>       if env["REQUEST_METHOD"] == "HEAD"
>         body.close if body.respond_to? :close
>         [status, headers, []]
>       else
>         [status, headers, body]
>       end
>     end

OK, I think you were hitting another problem because you were lacking
Rack::ContentType

Try the following:
-----------------------8<---------------------
require 'rack'
use Rack::ContentLength # less ambiguous than Rack::Chunked adding '0'
use Rack::Head
use Rack::ContentType
run lambda { |env| [200, {}, []] }
-----------------------8<---------------------

I added the Rack::ContentLength (it's already in the default middleware
stack) since I believe Rack::Chunked adding the '0' is a violation of
rfc2616... I'll need to read more closely to be sure.

> >>    HTTP/1.1 500 Internal Server Error
> > 
> >> As you can see, not only is there a zero-length chunked encoding body,
> >> but for some unknown reason there is a 500 response with no body as
> >> well.
> > 
> > Try using "-d" on the command-line to enable debugging to see what the
> > error is (and check the logs/stderr output).
> 
>     Exception `Errno::ENOTCONN' at /Users/titanous/.gem/ruby/1.9.3/gems/unicorn-4.6.2/lib/unicorn/http_server.rb:565 - Socket is not connected

Ugh, that's an unfortunate side effect of the client closing the
connection, first :/

> > Also, what RACK_ENV (or -E/--env) are you using?  It could be the
> > incorrect HEAD response tripping Rack::Lint under development mode.
> 
> None, specified, I'm booting unicorn with no configuration or flags specified.

That defaults the RACK_ENV to to "development", so you got
Rack::ContentLength, Rack::Chunked, Rack::CommonLogger,
Rack::ShowExceptions and Rack::Lint


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