The document summarizes the process of migrating the PriceChirp application from Rails 2.3 to Rails 3.0. It took 3 weeks to complete the migration. Key steps included upgrading gems, fixing code to remove deprecation warnings, installing Bundler, adding tests for critical functionality, using the Rails_upgrade plugin, and addressing changes to Active Record, views, and other areas of the framework. Challenges included upgrading plugins like Restful Authentication to Devise and converting from Prototype to jQuery for unobtrusive JavaScript support.

1. Migrating PriceChirp to Rails 3.0
Steven Evatt
Blog: http://www.evatt.com/blog
Web: http://PriceChirp.com
Twitter: @sevatt
Houston-RoR Nov 2010
The pain points

2. 2
Today We'll Cover:

Why Upgrade?

Pain points / Issues

Tips

Take Aways

3. 3
Full Disclosure

PriceChirp is my main side project designed to
help people (myself included) save money on
Amazon

My background is in Perl

4. 4
Why???

Gem ecosystem is starting to require Rails 3.0

Too many deprecation notices

5. 5
How much work was it?

3 weeks of nights / weekends

According to svn

Paths added 67

Paths modified 112

Paths removed 45

Replaced Restful_Authentication with Devise

Converted from Prototype to UJS jQuery

6. 6
Where to start?

Upgrade to Rails 2.3.9

Upgrade Gems

Fix code to remove deprecation message

Bundler

Have test for critical functionality

Install Rails_upgrade plugin

Make a new branch in your source control

7. 7
Source Control

Svn copy http://svn...com/pricechirp/trunk/
http://svn...com/pricechirp/branches/migrate_to_rails
3

Svn checkout
http://svn...com/pricechirp/branches/migrate_to_rails
3 migrate

8. 8
Plugin → Rails_upgrade

Documentation out of order and gives wrong
syntax for rails command

Mostly run from rails 2.3

Useful rake tasks

Rake rails:upgrade:check

Rake rails:upgrade:backup

Rake rails:upgrade:routes

Rake rails:upgrade:gems

Rake rails:upgrade:configuration

9. 9
Installing Rails 3

Rails new .

Creates a rails3 project
with the name of the
current directory

If directory name is
migrate:

Application name is
Migrate::Application

Must update in 12 places
to change

10. 10
Bundler

Bundler manages an application's dependencies
through its entire life across many machines
systematically and repeatably.

Gemfile

gem “rack”, “~>1.1”

gem “rspec, :requires => “spec”

It doesn’t take long before you want to use
bundler on all projects

11. 11
Bundler II

Passenger is not ignoring my Gemfile :test,
:development block in production

To get bundler to work with capistrano:

Add to deploy.rb:
require "bundler/capistrano"

12. 12
Upgrade Gems

gem ‘will_paginate’, ‘~> 3.0.pre2’, :require =>
‘will_paginate’

factory_girl_rails => compatibility mode

13. 13
Passenger

Apache configuration changed

from:
RailsEnv development

to:
RackEnv development

14. 14
Upgrade Plugins

Restful Authentication → Devise

copy crypted_password => encrypted_password

copy salt => encrypted_salt

set confirmed date

nil is a valid salt with Restful Auth, not in Devise

Change helper methods
− :login_required → :authenticate_user!
− logged_in? → user_signed_in?

Exception_notification

15. 15
RAILS_ENV and RAILS_ROOT
 RAILS_ENV → Rails.env
 Rails.env.production?
− If RAILS_ENV == “production”
− If Rails.env.production?
 RAILS_ROOT → Rails.root
 RAILS_CACHE → Rails.cache

16. 16
XSS protection is everywhere

Learn to love .html_safe.

All strings are not safe until flagged as safe.

17. 17
Views

forms helpers changed from <% to <%=

removed error_messages_for

link_to_remote

Use :remote => true

link_to

18. 18
UJS / jQuery

Converted rjs to erb

Converted from Prototype to jQuery

Get jQuery
− http://docs.jquery.com/Downloading_jQuery
− /public/javascripts/jquery-1.4.2.min.js

Copy rails.js from
github.com/rails/jquery-ujs/raw/master/src/rails.js

:remote => true

19. 19
Active Record Changes

passing options hash containing :conditions,
:include, :joins, :limit, :offset, :order,
:select, :readonly, :group, :having, :from,
:lock to any of the ActiveRecord provided
class methods, is now deprecated.

Find → where

find_by_x('xxx') => where(:x => ‘xxx’).first

where(‘b like ?’, value)

20. 20
Active Record “Bug”

select('distinct(x)') is ignored when passed to
.count
Example
Item.where('updated_at < ?',
1.days.ago ).select('distinct(asin)').all
Produces the following query:
Item Load (6.3ms) SELECT distinct(asin) FROM `items`
WHERE (updated_at < '2010-10-16 01:06:05')

21. 21
Active Record “Bug” II
Now, when we use .count instead of .all, the .select call
is ignored:
Item.where('updated_at < ?',
1.days.ago ).select('distinct(asin)').count
Yields:
SQL (5.4ms) SELECT COUNT(*) AS count_id FROM
(SELECT 1 FROM `items` WHERE (updated_at <
'2010-10-16 01:09:55')) AS subquery

22. 22
Active Record “Bug” III

Work around
Put a .all before the .count
Item.where('updated_at < ?',
1.days.ago ).select('distinct(asin)').all.count
Issue
If you attempt to use :group ie .count(:group => :asin) you
get an error

More Info on “bug”

https://rails.lighthouseapp.com/projects/8994/
tickets/5698-select-ignored-in-subquery-
when-querying-with-count

23. 23
Custom to_s formatting for dates
Example: Time.now.to_s(:js)

From:
ActiveSupport::CoreExtensions::Time::Conversions::DATE_FOR
MATS.merge!(:js => ‘%m %d, %Y %H:%M:%S’)

To:
Time::DATE_FORMATS[:js] = ‘%m %d, %Y %H:%M:%S’

24. 24
Logging Rails.cache Activity

By default, Rails3 does not log Rails.cache activity
Cache read: user.default
Cache fetch_hit: user.default
Cache read: user.count ({:expires_in=>300 seconds})
Cache generate: user.count ({:expires_in=>300 seconds})
Cache write: user.count ({:expires_in=>300 seconds})

To enable logging
In environment.rb
Rails.cache.logger ||= Rails.logger

25. 25
Action Mailer

Action_mailer defaults to :smtp although
everything says it defaults to :sendmail
config.action_mailer.delivery_method = :sendmail

Action_mailer requires
default_url_options[:host] to be defined
config.action_mailer.default_url_options[:host] = {
:host => ‘pricechirp.com’ }

26. 26
script/* replaced by script/rails

script/rails replaces all the scripts that used to
be in the script directory
Safe to remove: about, console, dbconsole, destroy
generate, plugin, runner, and server

27. 27
RSS

Had to wrap my
“xml.description” output
in a CDATA block for it
to display
<![CDATA[
…
]]>

28. 28
Validate-on-callback methods

validate_on_create
validate :x, :on => :create

29. 29
Remove Debugging Statements

logger.info request.inspect
Rails 2.3.9 Rails 3.0
request.inspect 5.9k 330k

30. 30
Mime::Type
Error:
A ActionView::MissingTemplate occurred in pages#index:
Missing template pages/index with {:locale=>[:en, :en],
:handlers=>[:builder, :erb, :rjs, :rhtml, :rxml], :formats=>[:"text/*"]} in
view paths ….
actionpack (3.0.1) lib/action_view/paths.rb:15:in `find'
Solution:
In /config/initializers/mime_types.rb, add:
Mime::Type.register “text/*”, :html

31. 31
Current Issues I
A ActionController::UnknownHttpMethod occurred in #:
PROPFIND, accepted HTTP methods are get, head, put,
post, delete, and options actionpack (3.0.1)
lib/action_dispatch/http/request.rb:59:in `request_method'

32. 32
Current Issues II
Bundler – During a “cap deploy”
...
[pricechirp.com] executing command
** [out :: pricechirp.com] (in /home/pricechirp)
** [out :: pricechirp.com] Could not find gem 'rspec-rails (>= 2.0.1, runtime)' in any of
the gem sources.
** [out :: pricechirp.com] Try running `bundle install`.
command finished
*** [deploy:update_code] rolling back
...

33. 33
Take Aways

Upgrade / fix deprecated code as
best you can before you start

Use Rails_upgrade plugin

XSS Protection is everywhere

Syntax changes:

Views form helpers

Link_to_remote replaced with :remote => true

Active Record changes: .find → .where

Validate-on-callback

Configurations

There is a lot of deprecated
advice out there, remember
to check the dates

34. 34
Thanks for Coming!
Steven Evatt
Email: steven@evatt.com
Site: http://PriceChirp.com
Blog: http://www.evatt.com/blog
Twitter: @sevatt