Rails3 and MongoDB Quick Guide

Install MongoDB
Download:
http://www.mongodb.org/downloads
Extract the files to a directory(e.g, /opt/mongodb)

Create data directory:

$ sudo mkdir -p /data/db

Start MongoDB server:

$ sudo /opt/mongodb/bin/mongod

Start shell and connection to MongoDB server for test:

$ /opt/mongodb/bin/mongo
> db.foo.save( { a : 1} )
> db.foo.find()
> exit

Install Rails3 and mongo_mapper

sudo gem install rails
sudo gem install mongo_mapper
sudo gem install bson_ext

Create Rails project that use MongoDB
Create project:

$ rails new MongoDBTest --skip-active-record

Edit the Gemfile:

gem 'rails', '3.0.3'
gem 'mongo_mapper'
gem 'bson_ext'

Create config/initializers/mongo.rb:

MongoMapper.connection = Mongo::Connection.new('localhost', 27017)
MongoMapper.database = "MongoDBTest-production"

if defined?(PhusionPassenger)
  PhusionPassenger.on_event(:starting_worker_process) do |forked|
    MongoMapper.connection.connect_to_master if forked
  end
end

Create a model app/models/user.rb:

class User
  include MongoMapper:Document

  key :name
end

Start Rails Console for test:

$ rails console production
>> User.create(:name => "User A")
=> #<User name: "User A", _id: BSON::ObjectId('4d01c70d98d1b1072b000001')>
>> User.create(:name => "User B")
=> #<User name: "User B", _id: BSON::ObjectId('4d01c70f98d1b1072b000002')>
>> User.all
=> [#<User name: "User A", _id: BSON::ObjectId('4d01c70d98d1b1072b000001')>, #<User name: "User B", _id: BSON::ObjectId('4d01c70f98d1b1072b000002')>]