Rails 3, apache & passenger, send_file sends zero byte files

I'm struggling with send_file with rails 3.0.9 running ruby 1.9, passenger 3.0.8 on apache on ubuntu lucid The xsendfile module is installed and loaded into apache

root~# a2enmod xsendfile
Module xsendfile already enabled

Its symlinked correctly in mods-enabled

lrwxrwxrwx 1 root root   32 Aug  8 11:20 xsendfile.load -> ../mods-available/xsendfile.load

config.action_dispatch.x_sendfile_header = "X-Sendfile" is set in my production.rb

using send_file results in zero byte files being sent to the browser

filepath = Rails.root.join('export',"#{filename}.csv")
if File.exists?(filepath)
  send_file fi开发者_开发百科lepath, :type => 'text/csv'
end

I believe the previous answer isn't the right way to go because, as far as I can tell, Apache isn't handling the downloads at all when this solution is applied, instead the rails process is. That's why the nginx directive, which shouldn't work, appears to. You get the same result by commenting out the config directive.

Another drawback (aside from tying up a rails process for too long) is that when the data streaming is handled by the rails process the response doesn't seem to send the content length header. So a user doesn't know how large the file they're downloading is, nor how long it will take (a usability problem).

I was able to get it to work by ensuring that mod_sendfile was properly included and loaded in my apache config, like so (this will be dependent on your apache install, etc.):

LoadModule xsendfile_module   /usr/lib64/httpd/modules/mod_xsendfile.so
...

# enable mod_x_sendfile for offloading zip file downloads from rails 
XSendFile on 
XSendFilePath /