gridfs.rb

# rails metal to be used with carrierwave (gridfs) and MongoMapper
# Now works with MongoMapper 0.7.5 and Mongo 1.0
# Begin/rescue is a bit lame, but mongo 1.0 doesn't have the exist? method yet (only from 1.0.1)

require 'mongo'

# Allow the metal piece to run in isolation
require(File.dirname(__FILE__) + "/../../config/environment") unless defined?(Rails)

class Gridfs
  def self.call(env)
    if env["PATH_INFO"] =~ /^\/images\/gridfs\/(.+)$/
      key = $1
      grid = Mongo::GridFileSystem.new(MongoMapper.database)
      begin
        grid.open(key, 'r') do |file|
          [200, {'Content-Type' => file.content_type, "Expires" => Time.now.advance(:days => 1).httpdate, 'Cache-Control' => 'max-age=31536000' }, [file.read]]
        end
      rescue
        [404, {'Content-Type' => 'text/plain'}, ['File not found.']]
      end
    else
      [404, {'Content-Type' => 'text/plain'}, ['File not found.']]
    end
  end
end

nice one, thanks for updating the old gist