Rack::GridFS

Rack:GridFS is a Rack middleware for creating HTTP endpoints for files stored in MongoDB’s GridFS. You can configure a prefix string which will be used to match the path of a request, and further look up GridFS files based on either their ObjectId or filename field.

For example,

GET '/gridfs/someobjectid'

If the prefix is “gridfs”, then the id will be be “someobjectid”.

You can also use Rack::GridFS::Endpoint as a rack endpoint if you want to handle routing another way

Mongo Driver Compatibility Notes

This version is currently based on mongo-1.2+. As there were significant changes to the GridFS API prior to v1.0, you may have luck with the git-tagged version 0.2.0 of this library with earlier versions of the driver.

Installation

gem install rack-gridfs

Features

Use as rack middleware or mount as a rack endpoint
File lookup using a path or object id
Chunked transfer encoding, keeps memory usage low
Content-Type header set using ‘mime-types’ gem
Last-Modified and Etag headers set automatically for conditional get support
Cache-Control header support
High availability when using replication sets

Usage

require 'rack/gridfs'
use Rack::GridFS, :prefix => 'gridfs', :hostname => 'localhost', :port => 27017, :database => 'test'

Options:

prefix: a string used to match against incoming paths and route to through the middleware. Default ‘gridfs’.
lookup: whether to look up a file based on :id or :path (example below). Default is :id.

You must also specify MongoDB database details:

hostname: the hostname/IP where the MongoDB server is running. Default ‘localhost’.
port: the port of the MongoDB server. Default 27017.
database: the name of the MongoDB database to connect to.
username and password: if you need to authenticate to MongoDB.

Alternatively you can pass in a Mongo::DB instance instead:

db: MongoMapper.database, or Mongoid.database for example.

Simple Sinatra Example

require 'rubygems'
require 'sinatra'

require 'rack/gridfs'
use Rack::GridFS, :database => 'test', :prefix => 'gridfs'

get /.*/ do
  "The URL did not match a file in GridFS."
end

Usage with Rails 2

To use Rack::GridFS in a Rails application, add it as middleware in application.rb or config/environments/*with something like this:

config.middleware.insert_after Rack::Runtime, Rack::GridFS,
  :prefix => 'uploads', :database => "my_app_#{Rails.env}"

Run rake middleware to decide for yourself where to best place it in the middleware stack for your app using the Rails convenience methods, taking into consideration that it can probably be near the top since it simply returns a “static” file or a 404.

Usage with Rails 3

To use in Rails 3, you can insert into the middleware stack as above, or mount the app directly in your routes (recommended). In config/routes.rb:

mount Rack::GridFS::Endpoint.new(:db => Mongoid.database), :at => "gridfs"

This allows for much more straightforward and sensible configuration, if you do not require other middleware in front of GridFS (Rack-based authorization, for instance).

Path (filename) Lookup

The :lookup => :path option causes files to be looked up from the GridFS store based on their filename field (which can be a full file path) rather than ObjectId (requests still need to match the prefix you’ve set). This allows you to find files based on essentially arbitrary URLs such as:

GET '/prefix/media/images/jane_avatar.jpg'

How filenames are set is specific to your application. We’ll look at an example with Carrierwave below.

NOTE: The Mongo Ruby driver will try to create an index on the filename field for you automatically, but if you are using filename lookup you’ll want to double-check that it is created appropriately (on slaves only if you have a master-slave architecture, etc.).

Carrierwave Example

Path lookup works well for usage with Carrierwave. As a minimal example with Mongoid:

# config/initializers/carrierwave.rb
CarrierWave.configure do |config|
  config.storage = :grid_fs
  config.grid_fs_connection = Mongoid.database
  config.grid_fs_access_url = "/uploads"
end

# app/uploaders/avatar_uploader.rb
class AvatarUploader < CarrierWave::Uploader::Base
  # (Virtual) path where uploaded files will be stored, appended to the
  # gridfs_access_url by methods used with view helpers
  def store_dir
    "#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end
end

# app/models/user.rb
class User
  include Mongoid::Document
  mount_uploader :avatar, AvatarUploader
end

# app/views/user/show.html.erb
<%= image_tag(@user.avatar.url) if @user.avatar? %>

This will result in URL paths like /uploads/user/avatar/4d250d04a8f41c0a31000006/original_filename.jpg being generated for the view helpers, and Carrierwave will store user/avatar/4d250d04a8f41c0a31000006/original_filename.jpg as the filename in GridFS. Thus, you can configure Rack::GridFS to serve these files as such:

config.middleware.insert_after Rack::Runtime, Rack::GridFS,
  :prefix => 'uploads', :lookup => :path, :database => "my_app_#{Rails.env}"