Rails 3 upgrade part 1: Booting the application

It’s time for another Rails upgrade! We all have our share of bad experiences and frustrations every time we upgrade a piece of software. Even for technical people who live and breath on the edge, upgrades are one of these things we try to avoid as much as possible. Still, there is always a sense of excitement in trying something new even if it adds problems to an already stable piece of code.

For a little background, I am upgrading a Rails app several of friends and I have written last year. The code is available at github.

In this post, I share the steps I did to boot the application. This doesn’t mean the upgrade went fine neither the app is ready to go. It only means all the required initialization are OK. In succeeding posts, I share my experiences in upgrading the app to a green state.

First, my environment.

  greg@piccolo:~/dev/projects/propsify3$ rvm info
      uname:        "Linux piccolo 2.6.31-22-generic #61-Ubuntu SMP Wed Jul 28 01:57:06 UTC 2010 i686 GNU/Linux"
      shell:        "bash"
      version:      "4.0.33(1)-release"
      version:      "rvm 0.1.44 by Wayne E. Seguin (wayneeseguin@gmail.com) [http://rvm.beginrescueend.com/]"
      interpreter:  "ruby"
      version:      "1.8.7"
      date:         "2010-06-23"
      platform:     "i686-linux"
      patchlevel:   "2010-06-23 patchlevel 299"
      full_version: "ruby 1.8.7 (2010-06-23 patchlevel 299) [i686-linux]"
  greg@piccolo:~/dev/projects/propsify3$ script/about
  About your application's environment
  Ruby version              1.8.7 (i686-linux)
  RubyGems version          1.3.7
  Rack version              1.0 bundled
  Rails version             2.3.2
  Active Record version     2.3.2
  Action Pack version       2.3.2
  Active Resource version   2.3.2
  Action Mailer version     2.3.2
  Active Support version    2.3.2
  Application root          /mnt/hgfs/greg-mini/dev/projects/propsify
  Environment               development
  Database adapter          postgresql
  Database schema version   20100113032723
  greg@piccolo:~/dev/projects/propsify3$ gem list
  *** LOCAL GEMS ***
  actionmailer (2.3.2)
  actionpack (2.3.2)
  activerecord (2.3.2)
  activeresource (2.3.2)
  activesupport (2.3.2)
  geokit (1.5.0)
  json (1.4.5)
  mime-types (1.16)
  oauth (0.4.1)
  pg (0.9.0)
  rails (2.3.2)
  rake (0.8.7)
  RedCloth (4.2.2)
  twitter_oauth (0.3.2)
  greg@piccolo:~/dev/projects/propsify3$ ls vendor/gems/
  authlogic-2.1.3  geokit-1.5.0  haml-2.2.16  macaddr-1.0.0  twitter_oauth-0.3.2  uuid-2.1.0
  greg@piccolo:~/dev/projects/propsify3$ ls vendor/plugins/
  acts_as_commentable        geokit-rails     is_taggable   thinking-sphinx      will_paginate
  declarative_authorization  gravatar-plugin  jrails        validates_date_time
  exception_notification     haml             subdomain-fu  vote_fu

Step 1: Install rails 3

gem install rails –pre

Step 2: Install the plugin tool

script/plugin install git://github.com/rails/rails_upgrade.git

Step 3: Show upgrade checklist

rake rails:upgrade:check

This task lists the items you should watch out for when doing the upgrade. You don’t need to fix everything right away (some are deprecation notice) but review the checklist nevertheless.

Step 4: Generate the new routes

rake rails:upgrade:routes

This task reads the current config/routes.rb and outputs a Rails 3 version.
Don’t worry, it doesn’t override your routes file. Keep this in a safe place for later use.

IMPORTANT: I actually didn’t realize I did the right thing until after the actual code upgrade. When I tried generating the new routes after the code change, it outputted an empty block. I have no idea if this is unique to my case but just to be sure, generate the routes beforehand and keep a copy.

Step 5: Create Gemfiles


Next is to generate the file ‘Gemfile’. In Rails 2, the gems you need are listed in config/environment.rb while in Rails 3 the gems are listed in the Gemfile. Gemfile is used by the program ‘bundler’ to manage the gems required by your application. Unfortunately, this task didn’t include the gems I listed in environment.rb so I have to add it later.

Step 6: Backup your files


I hope you are working on another branch (or a copy) but just in case you are not, run this task to make copies of the files that will be affected during the upgrade.

Now comes the juicy part.

Step 7: Generate the Rails 3 app on top of your Rails 2 app

rails new propsify3 -d postgresql

Run this command in your app’s parent folder. In my case, my app’s name and pathname is ‘propsify3’ and I am using postgresql as my database. This command created and replaced a bunch of files. Since you’ve backed-up everything, there’s nothing to worry.

Step 8: Move code from environment.rb to application.rb

Your new config/environment.rb file looks like it went through a rigorous diet. You can leave this file for now. What is important now is you move the initializer code from your config/environment.rb.rails2 to config/application.rb. These are the config.* lines except the config.gem which goes to Gemfile.

Step 9: Convert the new routes

You can still use the existing routes until 3.1 but since there’s a tool to help you migrate, I suggest doing it. At this point, when I tried the rails:upgrade:routes, no routes were generated. So make sure you generate the routes before Step 7.

Step 10: Delete new_rails_defaults.rb

rm config/initializers/new_rails_defaults

Step 11: Upgrade the plugins and gems

Many plugins are now available as gems. Check your plugins and gems at http://railsplugins.org. In my case, the following plugins were converted to gems:


Unfortunately, the plugins below are not yet ready for Rails 3. I removed them for now and all code that references them.


IMPORTANT: In your Gemfile, make sure you check specify the right version that is compatible with Rails 3. Some gems are still in the pre-release version and will not be downloaded if you don’t specify a version in your Gemfile. For example, this is a snippet from my Gemfile:

  gem 'pg'
  gem 'acts_as_commentable'
  gem 'declarative_authorization'
  gem 'haml'
  gem 'thinking-sphinx', '2.0.0.rc1', :require => 'thinking_sphinx'
  gem 'will_paginate', '3.0.pre2'
  gem 'uuid'
  gem 'geokit'

Step 12: Update initialization code

After step 10 you are good to go, if you’re lucky. In my case, I had to remove some patches and change code to boot the application.


This fails in Rails 3 because core extensions have been moved out of their modules and are now included in classes they extend. For example, to fix the date format problem do:


Step 13: Boot the app

rails server

Yay! If you are wondering what happened to script/server command, Rails went the “Merb way” and consolidated the script/* commands into the rails script.

By now, you should see the famous Rails’ “Welcome aboard” message in your browser.

Step 14: Remove public/index.html

Now, you can try if your application is working.

There are still more work to do like moving to the ActiveRecord/ActiveRelation API and removing the deprecation notices. Before moving on, I still need to fix the problems in my routes and unsupported gems which I will tackle in my next post.


5 thoughts on “Rails 3 upgrade part 1: Booting the application

  1. I had the same problem with the routes file. It’s okay to laugh at me for this.

    So, I guess I assumed that rake rails:upgrade:routes would be reading from the backed up routes.rb.rails2 file but it read from routes.rb. In my case I was doing ….

    rake rails:upgrade:routes > config/routes.rb

    Obviously that’s going to generate an empty file because I had already removed routes.rb. I shouldn’t have drank that big ol’ glass of derp for breakfast.

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