timeout when acting as a cache proxy

Hello,
  
  I've written a small ruby cgi that acts as a proxy for file downloads.
  If the requested file is in the cache, it's sent to the client
  directly. If not, it is fetched from its remote location and it's sent
  to the client at the same time (with req.read_body { block }).

  A very simplified version of it follows; the downloaded file is large
  enough that it takes more than 5min to be downloaded in my system.
  When run as a CGI, all goes fine. When using modruby, however, I get
  the following error exactly after 270 seconds:

mod_ruby: /var/www/adeodato/cgi/timeout.rbx:5:in `rbuf_fill': timeout (270 sec) (Apache::TimeoutError)
mod_ruby:   from /usr/lib/ruby/1.8/net/protocol.rb:196:in `timeout'
mod_ruby:   from /usr/lib/ruby/1.8/timeout.rb:55:in `timeout'
mod_ruby:   from /usr/lib/ruby/1.8/net/protocol.rb:196:in `rbuf_fill'
mod_ruby:   from /usr/lib/ruby/1.8/net/protocol.rb:128:in `read'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:1735:in `read_body_0'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:1697:in `read_body'
mod_ruby:   from /var/www/adeodato/cgi/timeout.rbx:17
mod_ruby:   from /var/www/adeodato/cgi/timeout.rbx:15:in `request'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:835:in `reading_body'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:835:in `request'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:823:in `request'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:821:in `start'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:821:in `request'
mod_ruby:   from /usr/lib/ruby/1.8/net/http.rb:734:in `request_get'
mod_ruby:   from /var/www/adeodato/cgi/timeout.rbx:15
mod_ruby:   from /usr/lib/ruby/1.8/apache/ruby-run.rb:53:in `load'
mod_ruby:   from /usr/lib/ruby/1.8/apache/ruby-run.rb:53:in `handler'

  Is this a known behavior of modruby, and I should be just rescueing
  timeouts, or there is a better solution. Perhaps something is wrong
  with my code?

  This is the script, thanks in advance:

------------------------8<------------------------------------------------------
#! /usr/bin/ruby -w

require 'cgi'
require 'uri'
require 'net/http'

Apache.request.sync_output = true if defined? MOD_RUBY

file = "http://ftp.de.debian.org/debian/pool/main/o/openoffice.org/openoffice.org-bin_1.1.3-6_i386.deb"

uri = URI.parse(file)

http = Net::HTTP.new(uri.host, uri.port)

http.request_get(uri.request_uri) do |r|
  print CGI.new.header('Content-Length' => r['Content-Length'])
  r.read_body { |seg|
    print seg
    # in the real cgi, I also do this:
    # somefile.print seg
  }
end
------------------------8<------------------------------------------------------

-- 
Adeodato Simó
    EM: asp16 [ykwim] alu.ua.es | PK: DA6AE621
 
There is no man so good who, were he to submit all his thoughts to the
laws, would not deserve hanging ten times in his life
                -- Michel de Montaigne