There is another know issue with Lighttpd:
http://github.com/rack/rack/blob/master/KNOWN-ISSUES
Maybe they're related?

//Magnus Holm


On Fri, Aug 28, 2009 at 16:37, bones <boesemar@googlemail.com> wrote:

>
> I am porting my application from ruby fcgi to rack which is in
> production using the Lighttpd webserver.
>
> I noticed that lighttpd doesn't send PATH_INFO or QUERY_STRING so I
> used to patch it by reconstructing it from REQUEST_URI. Now with Rack
> I have exactly the same situation. Rack::Request.GET is empty. This
> fix on the environment makes it working:
>
> class RackApp
>
>  def fix_env(ec)
>       if (ec['PATH_INFO'].to_s.empty?) then
>          pi =  ec['REQUEST_URI']
>          pi = pi[0..(pi.index('?')-1)] if pi.include?('?')
>          ec['PATH_INFO'] = pi
>       end
>
>       if (ec['QUERY_STRING'].to_s.empty?) then
>          ec['QUERY_STRING'] = ec['REQUEST_URI'].include?('?') ?
>              ec['REQUEST_URI'].scan(/.?\?(.*)/)[0][0] :
>              ""
>       end
>       ec
>  end
>
>  def call(env)
>    Rack::Request.new(fix_env(env))
>   # [...]
>  end
> end
>
>
> As far as I know Lighttpd and Rails (which used Rack?!) is a popular
> combination - so I am quiet surprised that I don't find anything
> related on the web. Especially - shouldn't that be implemented into
> Rack's CGI/FastCGI Handler?
>
> Cheers,
> Martin
>