Upgrading to Rails 3 on an active master branch

Changing the wheels on the bus at 80 mph
Andrew Bloomgarden and Julian Giuca
RailsConf 2013

Long-running branches are painful, but upgrading to Rails 3 requires one if you can't stop development, right? Wrong! At New Relic, we worked on upgrading to Rails 3 on master while letting development continue in Rails 2. We patched Bundler, built a backwards-compatible boot sequence, and punched ActiveScaffold in the face. Other developers, meanwhile, released 1400 commits worth of work without noticing any changes. We talk about what we did, why we did it, and why we think this approach can help developers get over the hurdle into the Rails 3 promised land.

Transcript

1. UPGRADING TO RAILS 3 Changing the wheels on the bus at 80mph (or 128.784 kph for everyone else) Andrew Bloomgarden Julian Giuca
2. Andrew introduction Andrew Bloomgarden @aughr 2
3. Julian Giuca @juliangiuca 3
4. Julian Giuca @juliangiuca 3
5. Julian Giuca @juliangiuca 3
6. Julian Giuca @juliangiuca 3
8. Overview 5 You can dual boot Rails 2 and Rails 3
9. Do try this at home! 6
10. Let’s talk about numbers... 7
11. Rails versions in the wild 2.x.x 3.x.x 8 Number of accounts
12. 2.2.2# 2.2.3# 2.3.2# 2.3.4# 2.3.5# 2.3.8# 2.3.10# 2.3.11# 2.3.12# 2.3.14# 2.3.15# 3.0.1# 3.0.3# 3.0.5# 3.0.11# 3.0.15# 3.0.18# 3.0.19# 3.1.1# 3.2.1# 3.2.8# 3.2.11# 3.2.13# Rails versions with >1 server 2.x.x 3.x.x Number of accounts
13. Rails version vs number of server 10
14. Upgrading to Rails 3 1. Procrastinate 2. Goals 3. Feature Branch 4. Fix tests 5. Merge 6. Push 7. Cross fingers 8. Fix Production 11
15. Putting it off Rearchitecting the app first Do it all in a big spike! Have a ruby_19 branch STUPID THINGS WE TRIED 12
16. Rails 3? Why now? 13
17. Rails 3? Why now? Someone will make upgrading easier soon! 13
18. Rails 3? Why now? Someone will make upgrading easier soon! Oh man, this is going to be awful. 13
19. Gems are leaving us behind 14
20. Gems are leaving us behind 14
21. Come and work on our Rails 2.3 app! 15
23. Upgrading to Rails 3 1. Procrastinate 2. Goals 3. Feature Branch 4. Fix tests 5. Merge 6. Push 7. Cross fingers 8. Fix Production 17
24. A bit of history 18
25. A bit of history Move to Rails 2.0.1 18
26. A bit of history 18
27. A bit of history Rails 2.3.14 70,000 application LOC 59,000 test LOC 18
28. Don’t break the world 19
29. Keep everyone happy not this this this this 20
30. Keep ourselves happy CONFLICT (content): … CONFLICT (content): … CONFLICT (content): … ⋮ CONFLICT (content): … Automatic merge failed; fix conflicts and then commit the result. 21
31. Upgrading to Rails 3 1. Procrastinate 2. Goals 3. Feature Branch 4. Fix tests 5. Merge 6. Push 7. Cross fingers 8. Fix Production 22
34. I’m looking at you Rails 1.2.2 people 25
35. I’m looking at you Rails 1.2.2 people 25
36. Gemfile platforms :ruby_18 do gem 'ruby-debug' end platforms :ruby_19 do gem 'debugger' end 26
38. Monkey patched! 27
39. In the Gemfile if ENV.include?("USE_RAILS_3") class Bundler::Dsl if !self.method_defined?(:to_definition_without_rails3_lockfile) alias_method :to_definition_without_rails3_lockfile, :to_definition end def to_definition(old_lockfile, unlock) current = File.expand_path(Dir.pwd) filename = File.join(current, "Gemfile_rails3.lock") lockfile = Pathname.new(filename) to_definition_without_rails3_lockfile(lockfile, unlock) end end module Bundler::SharedHelpers def default_lockfile current = File.expand_path(Dir.pwd) filename = File.join(current, "Gemfile_rails3.lock") lockfile = Pathname.new(filename) Pathname.new(lockfile) end end end 28
40. Two Gemfile.lock files 29
41. Gemfile if is_rails3 gem 'rails', '3.0.19' gem 'lighthouse-api', '~>2.0.0' gem 'dalli', '~> 2.3.0' gem 'jquery-rails', '~>2.1' gem 'active_reload' else gem 'rails', '2.3.15' gem 'lighthouse-api', '~>1.1.0' gem 'dalli', '~> 1.0.4' end 30
42. # Booting in Rails 3 mode $ export USE_RAILS_3=true $ bundle install $ rails server 31
43. Upgrading to Rails 3 1. Procrastinate 2. Goals 3. Feature Branch 4. Fix tests 5. Merge 6. Push 7. Cross fingers 8. Fix Production 32
44. Upgrading to Rails 3 1. Procrastinate 2. Goals 3. Feature Branch 4. Fix tests 5. Merge 6. Push 7. Cross fingers 8. Fix Production Improved! 32
45. From an idea to production 1. Procrastinate 2. Goals 3. Onto master 4. Getting it to work 5. Rollout 6. Lessons learned 33
46. From an idea to production 1. Procrastinate 2. Goals 3. Onto master 4. Getting it to work 5. Rollout 6. Lessons learned 34
47. Make it easy for everyone # Rails 2 $ script/server # Rails 3 $ script/server3 35
48. From an idea to production 1. Procrastinate 2. Goals 3. Onto master 4. Getting it to work 5. Rollout 6. Lessons learned 36
49. Onto master 1. Boot Rails 3 2. Dual boot 3. Unbreak Rails 2 4. Merge upstream 37
50. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2
51. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3
52. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3
53. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3
54. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3 Dual boot
55. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3 Dual boot
56. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3 Dual boot
57. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3 Dual boot Restore Rails 2
58. Unbreak Rails 2 Boots Rails 2 Runs Rails 2 Boots Rails 3 Runs Rails 3 Rails 2 Boot Rails 3 Dual boot Restore Rails 2
59. Onto master 1. Boot Rails 3 2. Dual boot 3. Unbreak Rails 2 4. Merge upstream 39
60. From an idea to production 1. Procrastinate 2. Goals 3. Onto master 4. Getting it to work 5. Rollout 6. Lessons learned 40
61. Dual-booting that works Rails 2.3 Rails 3 config/boot.rb requires Rails requires Bundler config/environment.rb loads, configures, and initializes the app initializes the app config/application.rb doesn’t exist loads and configures the app 41
62. Dual-booting that works Rails 2.3 Rails 3 config/boot.rb requires Rails requires Bundler config/environment.rb loads, configures, and initializes the app initializes the app config/application.rb doesn’t exist loads and configures the app 41
63. Just make it work 42
64. config/boot.rb if ENV.include?("USE_RAILS_3") require 'rubygems' # Set up gems listed in the Gemfile. ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__) require 'bundler/setup' 43 else # 123 lines that load Rails # All that for this: Rails.boot! end
65. config/boot.rb if ENV.include?("USE_RAILS_3") require 'rubygems' # Set up gems listed in the Gemfile. ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__) require 'bundler/setup' 43 else # 123 lines that load Rails # All that for this: Rails.boot! end
66. config/boot.rb if ENV.include?("USE_RAILS_3") require 'rubygems' # Set up gems listed in the Gemfile. ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__) require 'bundler/setup' 43 else # 123 lines that load Rails # All that for this: Rails.boot! end
67. config/environment.rb # Load the rails application require_relative "application" if CoreAppConfig.is_rails3? # Initialize the rails application RpmSite::Application.initialize! end 44
68. config/application.rb module NewRelicApplicationConfig def self.rails3_config(config) # Do Rails 3 stuff common_config(config) end def self.rails2_config(config) # Do Rails 2 stuff common_config(config) end def self.common_config(config) # ... end end 45
69. config/application.rb 46 if is_rails3 require 'rails/all' Bundler.require(:default, Rails.env) module RpmSite class Application < Rails::Application ::NewRelicApplicationConfig.rails3_config(config) end end else Rails::Initializer.run do |config| ::NewRelicApplicationConfig.rails2_config(config) end end
70. config/application.rb 46 if is_rails3 require 'rails/all' Bundler.require(:default, Rails.env) module RpmSite class Application < Rails::Application ::NewRelicApplicationConfig.rails3_config(config) end end else Rails::Initializer.run do |config| ::NewRelicApplicationConfig.rails2_config(config) end end
71. config/application.rb 46 if is_rails3 require 'rails/all' Bundler.require(:default, Rails.env) module RpmSite class Application < Rails::Application ::NewRelicApplicationConfig.rails3_config(config) end end else Rails::Initializer.run do |config| ::NewRelicApplicationConfig.rails2_config(config) end end
72. Have tests you trust 47
73. Use CI 48
74. Upgrade dependencies on master 49
75. BackgroundJob to Resque Bj.submit 'script/background/do_something.rb', :email => DEV_TEAM 50
76. Never again def getopts opts = {} if RUBY_VERSION.to_f >= 1.9 # In 1.9 this throw/catch/getopts nonsense breaks lambda do |*args| keys, default, ignored = args [keys].flatten.each do |key| [key, key.to_s, key.to_s.intern].each do |key| return opts[key] if opts.has_key?(key) end end return default end else # In 1.8 you can't return across threads lambda do |*args| keys, default, ignored = args catch('opt') do [keys].flatten.each do |key| [key, key.to_s, key.to_s.intern].each do |key| throw 'opt', opts[key] if opts.has_key?(key) end end default end end end end 51
77. Add an abstraction layer Bj.submit 'script/background/do_something.rb', :email => DEV_TEAM 52
78. Add an abstraction layer Async::Command.new( 'script/background/do_something.rb' ).notify(DEV_TEAM).enqueue 52
79. Use Resque or BackgroundJob class Async::Command < Async::Job if CoreAppConfig.use_resque? include Async::ResqueJob extend Resque::Plugins::History else include Async::BjJob end # ... end 53
80. Finally, use Resque 54
81. Branch by abstraction 55 The problem being with feature branches is that the current state of any one of them might be unable to be deployed for a number of weeks while the team gets it right. Those branches just end up running and running …. – Paul Hammant
82. Branch by abstraction 55 Branch by abstraction: a pattern for making large-scale changes to your application incrementally on mainline. – Jez Humble
83. Punt when you can 56
84. ActiveSupport::Deprecation.silenced = true 57
85. Your old routes still work RpmSite::Application.routes.draw do |map| Jammit::Routes.draw(map) # ... end 58
86. Your old routes still work RpmSite::Application.routes.draw do |map| Jammit::Routes.draw(map) # ... end 58
87. Your old mailers still work class AccountMailer < ApplicationMailer def new_account(account, user, subscription) headers['Errors-to'] = BOUNCE_ACCOUNT from BILLING_ACCOUNT subject "New Relic invoice account request" recipients INVOICE_RECIPIENT @account = account @user = user @subscription = subscription end end 59
88. Your old mailers still work class AccountMailer < ApplicationMailer def new_account(account, user, subscription) headers['Errors-to'] = BOUNCE_ACCOUNT from BILLING_ACCOUNT subject "New Relic invoice account request" recipients INVOICE_RECIPIENT @account = account @user = user @subscription = subscription end end 59
89. Your old models (can) still work self.store_full_sti_class = false 60
90. Your old views (can) still work helper PrototypeHelper clear_helpers 61
91. Your error handling (can) still work # included into ApplicationController def rescue_with_handler(e) if super # ActiveSupport::Rescuable true else rescue_action_in_public e true end end 62
92. Temporarily ugly 63 if CoreAppConfig.is_rails3? # do something else # do something else end
93. From an idea to production 1. Procrastinate 2. Goals 3. Onto master 4. Getting it to work 5. Rollout 6. Lessons learned 64
94. We want YOU to test! 65 To run in Rails 3, just run script/server3
95. Extensive manual testing 66 Database Data collection UI Rails 3 UI
96. Make everyone a tester 67
97. Turn on Rails 3 by default -is_rails3 = ENV.include?("USE_RAILS_3") +is_rails3 = !ENV.include?("USE_RAILS_2") 68
98. Incompatible sessions 69 ActionDispatch::Session::SessionRestoreError (Original exception: uninitialized constant ActionController::Flash::FlashHash)
99. Incompatible sessions 69
100. Deploy a canary 70
101. Pause the world 71
102. Deploy all the servers 72
103. Oops 73
105. And we’re done! 75
106. And we’re done! 75
107. A few very tiny fires 76
108. Breaking the audit trail ActionController::Base.class_eval do cache_sweeper :audit_sweeper end Audit.add_observer(AuditSweeper.instance) class AuditSweeper < ActionController::Caching::Sweeper observe Audit end 77
109. Rushed Resque rollout 78
110. Punching ActiveScaffold in the face .../bundle/ruby/1.9.1/gems/ active_scaffold-3.0.26/lib/ active_scaffold/bridges/date_picker/ lib/datepicker_bridge.rb:127:in `binread': No such file or directory - .../public/ javascripts/active_scaffold/default/ date_picker_bridge.js (Errno::ENOENT) 79
111. Lost BackgroundJob instrumentation This page left intentionally blank 80
112. Tagging green build off of Rails 2 tests 81
113. Lots of cleanup 82
114. From an idea to production 1. Procrastinate 2. Goals 3. Onto master 4. Getting it to work 5. Rollout 6. Lessons learned 83
115. Lessons learned 1. Preorder the donuts your on-call engineers like 2. Deprecate ActiveScaffold 3. Schedule lots of time for firefighting and cleanup 84
116. •Get it into master as early as possible •Incremental everything •CI is your bestest childhood friend (and you secretly have a crush on them) The special magic pony sauce 85
117. newrelic.com/rails3_upgrade @aughr | @juliangiuca 86 We’re done (and we’re hiring)