Death By a Thousand Commits

On the 1st commit, things are getting started. On the 10th commit, the feature is live and users are giving feedback. On the 100th commit, users are delighted to be using the application. But on the 1000th commit, users are unhappy with the responsiveness of the application and the developers are struggling to move at the velocity they once were. Does this sound familiar?

We will go over some of the pieces of technical debt that can accumulate and can cause application performance and development velocity issues, and the strategies Clio uses to keep these kinds of technical debt under control.

Transcript

1. Death By a Thousand Commits Kyle d’Oliveira RailsConf 2019
2. About me Kyle d’Oliveira https://www.linkedin.com/in/doliveirakn https://github.com/doliveirakn
4. Technical Debt
5. Technical Debt
6. Technical Debt
7. Technical Debt Quadrants – Martin Fowler Reckless Prudent Deliberate Inadvertent
8. Technical Debt Quadrants – Martin Fowler Reckless Prudent Deliberate Inadvertent “What’s layering”
9. Technical Debt Quadrants – Martin Fowler Reckless Prudent Deliberate “We don’t have time for design” Inadvertent “What’s layering”
10. Technical Debt Quadrants – Martin Fowler Reckless Prudent Deliberate “We don’t have time for design” “We must ship now and deal with consequences” Inadvertent “What’s layering”
11. Technical Debt Quadrants – Martin Fowler Reckless Prudent Deliberate “We don’t have time for design” “We must ship now and deal with consequences” Inadvertent “What’s layering” “Now we know how we should have done it”
12. Paying down technical debt ▪ Deal with the consequences
13. Paying down technical debt ▪ Deal with the consequences ▪ Be proactive
14. Paying down technical debt ▪ Deal with the consequences ▪ Be proactive ▪ Invest in tools
15. Lessons ▪ Lesson 1 – Automate the debt away ▪ Lesson 2 – Clean up code you don't use ▪ Lesson 3 – Make keeping the lights on easier ▪ Lesson 4 – Keep the bad patterns out
16. Automate the debt away Lesson 1
17. N+1 Queries The silent performance tax
18. SELECT * FROM contacts SELECT * FROM emails WHERE contact_id = 1 SELECT * FROM emails WHERE contact_id = 2 SELECT * FROM emails WHERE contact_id = 3 SELECT * FROM emails WHERE contact_id = 4 SELECT * FROM emails WHERE contact_id = 5 SELECT * FROM emails WHERE contact_id = 6
19. SELECT * FROM contacts SELECT * FROM emails WHERE contact_id IN (1, 2, 3, 4, 5, 6)
20. class ContactsController < ApplicationController def index render json: Contact.limit(200) end end
21. class ContactSerializer < ActiveModel::Serializer attribute :id, :name end
22. [ { “id”:1, “name”: “Jordan” }, { “id”:2, “name”: “Erin” }, { “id”:3, “name”: “Anna” }, ]
23. class ContactSerializer < ActiveModel::Serializer attribute :id, :name has_one :email end
24. class ContactSerializer < ActiveModel::Serializer attribute :id, :name has_one :email end
25. class ContactSerializer < ActiveModel::Serializer attribute :id, :name has_one :email has_one :phone_number has_one :address has_one :emergency_contact end
26. class ContactsController < ApplicationController def index render json: Contact.includes(:email).limit(200) end end
27. Limitations ▪ Manual human effort
28. Limitations ▪ Manual human effort ▪ Only fixes one instance at a time
29. Limitations ▪ Manual human effort ▪ Only fixes one instance at a time ▪ Doesn’t handle associations no longer being needed
30. Automate the debt away Lesson 1 Tools
31. jit_preloader https://github.com/clio/jit_preloader
32. # Gemfile gem “jit_preloader” # config/initializers/jit_preloader.rb JitPreloader.globally_enable = true
35. 95 percentile with N+1 queries 95 percentile without N+1 queries
36. 99 percentile with N+1 queries 99 percentile without N+1 queries
37. Automate the debt away Lesson 1
38. Clean up code you don't use Lesson 2
41. Clean up code you don't use Lesson 2 Tools
42. TombstoneError = Class.new(StandardError) def Tombstone(date_of_death) exception = TombstoneError.new( “Code was laid to rest on #{date_of_death}” ) Bugsnag.notify(exception) end
43. class UsersController def index Tombstone(“2019-05-02”) # Original Behaviour end end
45. dead_code_detector https://github.com/clio/dead_code_detector
46. coverband https://github.com/danmayer/coverband
47. # Gemfile gem “dead_code_detector”
48. Deleted so far: 300 controller actions 1000 methods
49. Clean up code you don't use Lesson 2
50. Make it easier to keep the lights on Lesson 3
52. SELECT * FROM users
53. Make it easier to keep the lights on Lesson 3 Tools
54. Make it easier to keep the lights on Lesson 3 Tools
55. marginalia https://github.com/basecamp/marginalia
56. # Gemfile gem “marginalia”
57. SELECT * FROM users /* controller:users, action:index */
58. ActiveSupport::CurrentAttributes https://api.rubyonrails.org/classes/ActiveSupport/CurrentAttributes.html
59. class Current < ActiveSupport::CurrentAttributes attribute :user_id, :request_id end
60. class ApplicationController before_action do Current.user_id = current_user&.id Current.request_id = request.uuid end end
61. module Marginalia module Comment def self.user_id Current.user_id end def self.request_id Current.request_id end end end
62. Marginalia::Comment.component = [ :controller, :action, :user_id, :request_id ]
63. SELECT * FROM users /* controller:users, action:index, user_id:5, request_id:4cdd8083-5f10 */
64. ActiveSupport::Notifications https://api.rubyonrails.org/classes/ActiveSupport/Notifications.html
65. ActiveSupport::Notifications .subscribe(‘active_record.sql’) do |*args| event = ActiveSupport::Notifications::Event.new(*args) if event.duration > THRESHOLD # Do something end end
66. ActiveSupport::Notifications .subscribe(‘active_record.sql’) do |*args| event = ActiveSupport::Notifications::Event.new(*args) if event.duration > THRESHOLD exception = LongQueryException.new(“a clear message”) Bugsnag.notify(exception) end end
68. Make it easier to keep the lights on Lesson 3
69. Make it easier to keep the lights on Lesson 3
70. Keep the bad patterns out Lesson 4
71. begin file = Tempfile.new(“contact.csv”) csv = CSV.new(file) csv << [“id”, “name”] Contact.all.each do |contact| csv << [contact.id, contact.name] end ensure file.close file.unlink end
72. begin file = Tempfile.new(“contact.csv”) csv = CSV.new(file) csv << [“id”, “name”] Contact.all.each do |contact| csv << [contact.id, contact.name] end ensure file.close file.unlink end
75. Keep the bad patterns out Lesson 4 Tools
76. rubocop https://github.com/rubocop-hq/rubocop
79. Shitlist-driven development Shopify https://sirupsen.com/shitlists/ Florian Weingarten - RedDotRubyConf 2017
80. Shitlist = [ClassA, ClassB, ClassC] def push_job_that_does_crazy_things(klass) if Shitlist.include?(klass) # existing deprecated behavior else raise Shitlist::Error.new(“a clear message”) end end
81. RedisShitlist = [ Session, FragmentCache, AuthenticationTokens ] test “no new redis models introduced” do assert_equal RedisShitList, RedisModel.descendants end
83. Keep the bad patterns out Lesson 4
84. Lessons ▪ Lesson 1 – Automate the debt away – jit_preloader ▪ Lesson 2 – Clean up code you don't use – Tombstone – dead_code_detector – coverband ▪ Lesson 3 – Make keeping the lights on easier – marginalia/ActiveSupport::CurrentAttributes – ActiveSupport::Notifications ▪ Lesson 4 – Keep the bad patterns out – rubocop – Shitlist-driven development
85. Death By a Thousand Commits Kyle d’Oliveira RailsConf 2019