Patch for Mongo::GridIO to respond to each as required by the Rack API.

config.ru

# Patch Mongo::GridIO to contain an each method.
require File.join File.dirname(__FILE__), 'lib/kimono/grid_io'
Mongo::GridIO.send(:include, Kimono::GridIO)

# You probably want to implement something a bit smarter than just talking
# to localhost.
database = Mongo::Connection.new.db('kimono_production')

app = proc do |env|
  begin
    gridfs_file = Mongo::GridFileSystem.new(Mongoid.database).open(env["PATH_INFO"], 'r')
    [ 200, { 'Content-Type' => gridfs_file.content_type, 'Content-Length' => gridfs_file.file_length.to_s }, gridfs_file ]
  rescue
    message = 'Grid file not found.'
    [ 404, { 'Content-Type' => 'text/plain', 'Content-Length' => message.size.to_s }, message ]
  end
end

run app

grid_io.rb

require 'mongo'

module Kimono
  module GridIO

    def size
      (file_length / chunk_size) + (file_length % chunk_size > 0 ? 1 : 0)
    end

    def each
      size.times { yield read(chunk_size) }
    end
 
  end
end

jeremys_original_gridfs_controller.rb

require 'mongo'
        
class GridfsController < ActionController::Metal
  def serve
    gridfs_path = env["PATH_INFO"].gsub("/images/", "")
    begin
      gridfs_file = Mongo::GridFileSystem.new(Mongoid.database).open(gridfs_path, 'r')
      self.response_body = gridfs_file.read
      self.content_type = gridfs_file.content_type
    rescue
      self.status = :file_not_found
      self.content_type = 'text/plain'
      self.response_body = ''
    end
  end
end

routes.rb

Kimono::Application.routes.draw do

  # Patch Mongo::GridIO to contain an each method.
  require File.join Rails.root, 'lib/kimono/grid_io'
  Mongo::GridIO.send(:include, Kimono::GridIO)
  match "/gridfs/*path", :via => :get, :to => proc { |env|
    gridfs_path = env["PATH_INFO"].gsub("/gridfs/", "")
    begin
      gridfs_file = Mongo::GridFileSystem.new(Mongoid.database).open(gridfs_path, 'r')
      [ 200, { 'Content-Type' => gridfs_file.content_type, 'Content-Length' => gridfs_file.file_length.to_s }, gridfs_file ]
    rescue
      message = 'Grid file not found.'
      [ 404, { 'Content-Type' => 'text/plain', 'Content-Length' => message.size.to_s }, message ]
    end
  }


end

Your module Kimono::GridIO has got to be the most ridiculous implementation of a Ruby module I have ever seen. Surely you must know that modules, like classes, are supposed to hold instance methods, but unlike classes, they can be included into a class (or another module), adding those methods to the receiver. So why would you define an "included" hook that explicitely re-opens the class to define new methods instead of just defining methods directly in the module's body?

Also, still in Kimono::GridIO, but this time in #each: you should use "yield" instead of capturing the block in a "block" variable and then calling "block.call". The result will be the same, but it's just the right way to do it, less code noise and way more efficient.

In answer to your first question, probably because I have three small kids and don't get enough sleep :)

You're right about yield, I tend to think of the block as a method argument so prefer to see it visually in the method signature. I'll change it ASAP.

These are dumb mistakes. So is your tone. I'm letting it slide.

OK.

I know it sounded harsh, I'm sorry. But these are the kind of mistakes that shouldn't happen anymore given how well Ruby is documented now.