MONGOID

Get the Mongoid gem from rubygems.org:

gem install mongoid -v "2.0.0.beta.15"

For performance improvements you will want to also install the mongo c extensions if compatible with your system.

gem install bson_ext

For Rails applications add the gem dependency to your Gemfile:

gem "mongoid", "2.0.0.beta.15"
gem "bson_ext", "1.0.4"

Setup of the database connection itself is handled by using automatic configuration with a config/mongoid.yml. You can generate a mongoid.yml via the following command:

rails generate mongoid:config

Executing this will also switch your default ORM to Mongoid (i.e. rails g model will now generate Mongoid Documents as your models):

An example configuration is as follows, with the default values showing:

config/mongoid.yml:

defaults: &defaults
  host: localhost
  slaves:
    - host: slave1.local
      port: 27018
    - host: slave2.local
      port: 27019
  autocreate_indexes: false
  allow_dynamic_fields: true
  include_root_in_json: false
  parameterize_keys: true
  persist_in_safe_mode: false
  raise_not_found_error: true
  reconnect_time: 3

development:
  <<: *defaults
  database: control_development

test:
  <<: *defaults
  database: control_test

# set these environment variables on your prod server
production:
  <<: *defaults
  host: <%= ENV['MONGOID_HOST'] %>
  port: <%= ENV['MONGOID_PORT'] %>
  database: <%= ENV['MONGOID_DATABASE'] %>

Mongoid currently supports the following configuration options in the mongoid.yml shown above:

allow_dynamic_fields: When attributes are not defined as fields but added to an object, they will get fields added for them dynamically and will get persisted. This defaults to true, and if set to false an error will get raised when attempting to set a value that has no field defined.

autocreate_indexes: Defaults to false. When set to true Mongoid will attempt to create indexes each time a class is loaded. This is not recommended for any environment other than development or test.

include_root_in_json: Defaults to false. When set to true mongoid will include the name of the root document and the name of each association as the root element when calling #to_json on a model.

parameterize_keys: Tells Mongoid to convert basic special characters in composite keys to SEO friendly substrings. Defaults to true.

persist_in_safe_mode: Tells Mongoid to perform all database operations in MongoDB's safe mode. This will cause the driver to double check operations and raise an error if they failed. Defaults to false, switching to true will be safe but will be a performance hit.

raise_not_found_error: Will raise a Mongoid::Error::DocumentNotFound when attempting to find a document by an id that doesnt exist. Defaults to true, but when set to false will only return nil for the same query.

reconnect_time: Tells Mongoid the max time to attempt reconnection to the database if a connection failure has occured. Default is 3 seconds.

skip_version_check: If you are having issues authenticating against MongoHQ or MongoMachine because of access to the system collection being not allowed, set this to true.

You can define your own logger for Mongoid if you do not want to use the default Rails logger in your Rails' application.rb.

module MyApplication
  class Application < Rails::Application
    config.mongoid.logger = Logger.new($stdout, :warn)
  end
end

Now that you have a mongoid.yml you can't wait to delete that pesky database.yml, right? Do it and you'll start getting ActiveRecord errors all over the place. You don't need ActiveRecord unless you're trying to use Mongo in concert with a SQL database. Here's how you remove ActiveRecord from the most recent version of Rails 3:

• Open yourapp/config/application.rb
• Near the top, remove the line require 'rails/all' and add the following three lines so you end up with this:

require "action_controller/railtie"
require "action_mailer/railtie"
require "active_resource/railtie"

• Start up your app and welcome yourself to a life without ActiveRecord!

You can initialize Mongoid in it's configuration block, either by calling the above mentioned methods directly or using from_hash to load in a mongoid.yml:

Mongoid.configure do |config|
  name = "control_development"
  host = "localhost"
  config.master = Mongo::Connection.new.db(name)
  config.slaves = [
    Mongo::Connection.new(host, 27018, :slave_ok => true).db(name)
  ]
  config.persist_in_safe_mode = false
end

OR

file_name = File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
@settings = YAML.load(ERB.new(File.new(file_name).read).result)

Mongoid.configure do |config|
  config.from_hash(@settings[ENV['RACK_ENV']])
end