Lesscode

RubyConfChina 2015 talk

Transcript

1. Lesscode Xuejie Xiao @defmacro
3. What this talk is about
4. Simplicity
5. What this talk is NOT about
6. Micro services
7. Perfomance
8. Shitty Rails Clone
9. Software is hard • Daily changed features • Unreasonable Deadlines
13. Software is hard to make
14. How do we handle complexity?
15. What’s the simplest software?
16. No software at all! Zero complexity
17. But that’s unrealistic
18. What is simple? What is complex?
19. Simple vs. Easy • Simple • One fold/task • No interleaving • Defined by us • Easy • Near our capabilities • Defined by problems From Simplicity Matters @ RailsConf 2012 by Rich Hickey, https://www.youtube.com/watch?v=rI8tNMsozo0 Simple!
20. Complexity • Essential Complexity • Determined by the problem • Accidental Complexity • Exists because our tools are not perfect
21. Easy <=> Essential Complexity Simple <=> Accidental Complexity
22. Easy <=> Essential Complexity (Hard) Simple <=> Accidental Complexity (Complex)
23. We want to reduce accidental complexity! I.E., make software less complex
24. Accidental Complexity • Simple • Untwisted • Complex • Twisted From Simplicity Matters @ RailsConf 2012 by Rich Hickey, https://www.youtube.com/watch?v=rI8tNMsozo0
25. Question: how many moving parts are needed for a normal site?
26. Moving Parts • PostgreSQL • Cache(Redis) • Ruby App
27. Moving Parts • PostgreSQL • Cache(Redis) • Ruby App <= Required? <= Optional? <= Required?
28. Moving Parts • PostgreSQL • Cache(Redis) • Ruby App <= Required! <= Required! <= Required!
29. What do you think Redis is?
31. Redis as a database? R U kidding me?
32. From https://twitter.com/antirez/status/634693291590725632
33. So Redis as a database, how does that work?
34. Save a record HMSET User:1 email foo@bar.com name foo
35. What about model ID? INCR User:_id
36. Load a record HGETALL User:1
37. Update index SADD User:emails:foo@bar.com 1
38. Find by index SMEMBERS User:emails:foo@bar.com Then run HGETALL on each ID
39. Joint Query SINTERSTORE User:query:b0fca790 User:emails:foo@bar.com User:name:foo SMEMBERS User:query:b0fca790 Run whatever processing we need for each id DEL User:query:b0fca790
40. Don’t forget you have Lua at your fingertip! 1 local ctoken = redis.call('HGET', KEYS[1], '_cas') 2 if (not ctoken) or ctoken == ARGV[2] then 3 local ntoken 4 if not ctoken then 5 ntoken = 1 6 else 7 ntoken = tonumber(ctoken) + 1 8 end 9 redis.call('HMSET', KEYS[1], '_sdata', ARGV[1], 10 '_cas', ntoken, '_ndata', ARGV[3]) 11 return ntoken 12 else 13 error('cas_error') 14 end
41. Ohm http://ohm.keyvalue.org/
42. 1 class Event < Ohm::Model 2 attribute :name 3 reference :venue, :Venue 4 set :participants, :Person 5 counter :votes 6 7 index :name 8 end 9 10 class Venue < Ohm::Model 11 attribute :name 12 collection :events, :Event 13 end 14 15 class Person < Ohm::Model 16 attribute :name 17 end
43. 1 event = Event.create :name => "Ohm Worldwide Conference 2031" 2 event.id 3 # => 1 4 5 # Find an event by id 6 event == Event[1] 7 # => true 8 9 # Update an event 10 event.update :name => "Ohm Worldwide Conference 2032" 11 # => #<Event:0x007fb4c35e2458 @attributes={:name=>"Ohm Worldwide Conference"}, @_memo={}, @id="1"> 12 13 # Trying to find a non existent event 14 Event[2] 15 # => nil 16 17 # Finding all the events 18 Event.all.to_a 19 # => [<Event:1 name='Ohm Worldwide Conference 2031'>]
44. 1 event.attendees.add(Person.create(name: "Albert")) 2 3 # And now... 4 event.attendees.each do |person| 5 # ...do what you want with this person. 6 end
45. Moving Parts Now • Redis • Ruby App
46. Isn’t that simpler?
47. Let’s talk about tests
50. Ruby has gone too magical when it comes to tests
51. From https://github.com/rspec/rspec-core/issues/2067
52. What does expect(…).to return?
53. From https://relishapp.com/rspec/rspec-expectations/docs
54. Wait a sec, all you give me is an example?
55. This is CDD, not TDD
56. Copy(-paste) Driven Development
57. More documentation From https://relishapp.com/rspec/rspec-expectations/docs/compound-expectations
58. RubyDoc to the rescue From http://www.rubydoc.info/gems/rspec-expectations/RSpec/Expectations/ExpectationTarget#to-instance_method
59. Huh, Matcher object does what? From http://www.rubydoc.info/gems/rspec-expectations/RSpec/Matchers/DSL/Matcher
60. Complex Behavior • expect(…).to returns a Matcher object • You don’t know Matcher unless you read RSpec source code
61. MiniTest: better, but still magical From https://github.com/seattlerb/minitest/blob/master/lib/minitest/spec.rb
62. Let’s face it: not everyone likes this syntax obj.must_equal “foo” expect(obj).to eq(“foo”) Or
63. What’s wrong with this? assert_equal obj, “foo”
64. Cutest https://github.com/djanowski/cutest 118 LOC
65. Tests cannot be simpler 1 setup do 2 {:a => 23, :b => 43} 3 end 4 5 test "should receive the result of the setup block as a parameter" do |params| 6 assert params == {:a => 23, :b => 43} 7 end 8 9 test "should evaluate the setup block before each test" do | params| 10 params[:a] = nil 11 end 12 13 test "should preserve the original values from the setup" do | params| 14 assert 23 == params[:a] 15 end
66. How do we make the whole stack simple at CitrusByte
67. Our choice: Cuba http://cuba.is/
68. 0 3000 6000 9000 12000 Cuba 3.4.0 Sinatra 1.4.6 ActionPack 4.2.4 Cuba 3.4.0 has only 314 lines of code
69. Gems normally used together with Cuba Framework | LOC ---------------|--------------- mote | 33 shield | 98 scrivener | 97 ohm | 647 protest | 118 ost | 59 malone | 93 nobi | 127 clap | 28 gs | 43 dep | 213 Notice this is never about LOC, it’s about one library fulfills one purpose only
70. The whole stack is ~1556 lines of code • Read the source code! • Simple library, clear boundary • Easy to extend
71. AT&T M2X https://m2x.att.com/
72. Redis http://redis.io/
73. ChefsFeed http://www.chefsfeed.com/
74. Red Stamp https://www.redstamp.com/
75. Is Rails simple?
76. You might say: Rails feels easy to me! • Complicated constructs can be: • Familiar • Ready to use • But they are still complex, meaning they are: • Interleaved • Brings accidental complexity, which will bite you
77. Example time!
78. Hound https://houndci.com/ https://github.com/thoughtbot/hound
79. Punchgirls Job Board https://jobs.punchgirls.com https://github.com/punchgirls/job_board
80. Question: how many files are need for one request?
81. Route 1 Houndapp::Application.routes.draw do 2 # ... 3 4 resources :repos, only: [:index] do 5 with_options(defaults: { format: :json }) do 6 resource :activation, only: [:create] 7 resource :deactivation, only: [:create] 8 resource :subscription, only: [:create, :destroy] 9 end 10 end 11 12 # ... 13 end
82. Controller 1 class ActivationsController < ApplicationController 2 class FailedToActivate < StandardError; end 3 class CannotActivatePaidRepo < StandardError; end 4 5 before_action :check_repo_plan 6 7 def create 8 if activator.activate 9 analytics.track_repo_activated(repo) 10 render json: repo, status: :created 11 else 12 analytics.track_repo_activation_failed(repo) 13 render json: { errors: activator.errors }, status: 502 14 end 15 end 16 17 private
83. Controller (cont.) 1 def check_repo_plan 2 if repo.plan_price > 0 3 raise CannotActivatePaidRepo 4 end 5 end 6 7 def activator 8 @activator ||= RepoActivator.new(repo: repo, github_token: github_token) 9 end 10 11 def repo 12 @repo ||= current_user.repos.find(params[:repo_id]) 13 end 14 15 def github_token 16 current_user.token 17 end 18 end
84. Related action in ApplicationController 1 class ApplicationController < ActionController::Base 2 protect_from_forgery 3 4 before_action :force_https 5 before_action :capture_campaign_params 6 before_action :authenticate 7 8 helper_method :current_user, :signed_in? 9 10 private 11 # ... 12 13 def analytics 14 @analytics ||= Analytics.new(current_user, session[:campaign_params]) 15 end 16 17 # ... 18 end
85. Service Object 1 class RepoActivator 2 attr_reader :errors 3 4 def initialize(github_token:, repo:) 5 @github_token = github_token 6 @repo = repo 7 @errors = [] 8 end 9 10 def activate 11 activated = activate_repo 12 13 if activated 14 enqueue_org_invitation 15 end 16 17 activated 18 end 19 # ... 20 end
86. View or Serializer 1 class RepoSerializer < ActiveModel::Serializer 2 attributes( 3 :active, 4 :full_github_name, 5 :full_plan_name, 6 :github_id, 7 :id, 8 :in_organization, 9 :price_in_cents, 10 :private, 11 :stripe_subscription_id, 12 ) 13 # ... 14 end
87. How big is your screen?
88. I thought I was writing Ruby, not Objective-C?
89. Luckily, the action we showed is simple • No helpers • No so-called presenter or whatever objects • We assume you already know models • before_action is not abused
90. What about Cuba?
91. Routes that perform actions 1 on "application/:id/contact" do |id| 2 application = Application[id] 3 on application && company.posts.include?(application.post) do 4 on post, param("message") do |params| 5 mail = Contact.new(params) 6 if mail.valid? 7 message = JSON.dump(application_id: id, 8 subject: params["subject"], body: params["body"]) 9 Ost[:contacted_applicant].push(message) 10 res.redirect "/post/#{application.post.id}/applications" 11 else 12 session[:error] = "All fields are required" 13 render("company/post/contact", 14 title: "Contact developer", 15 application: application, message: mail) 16 end 17 end 18 end 19 end
92. Filters that validates requests 1 class Contact < Scrivener 2 attr_accessor :subject, :body 3 4 def validate 5 assert_present :subject 6 assert_present :body 7 end 8 end
93. Views that queries and assembles data 1 <section id="contact-applicant"> 2 <h2>Contact developer</h2> 3 4 <form action="/application/{{ application.id }}/contact" 5 method="POST"> 6 <!-- ... --> 7 8 <input type="text" name="message[subject]" 9 value="{{ message.subject }}" placeholder="Subject"> 10 11 <textarea name="message[body]" 12 placeholder="This mail will be sent to the developer"> 13 {{ message.body }} 14 </textarea> 15 16 <!-- ... --> 17 </form> 18 </section>
94. Is your screen nicer?
95. We do use helpers, but it’s more general 1 module DeveloperHelpers 2 # ... 3 4 def mote_vars(content) 5 super.merge(current_developer: current_developer) 6 end 7 8 def notfound(msg) 9 res.status = 404 10 res.write(msg) 11 halt(res.finish) 12 end 13 14 # ... 15 end
96. Choices in Rails
97. –David Heinemeier Hansson “Rails is omakase.”
98. People love to customize Rails • ActiveRecord vs. Sequel • Sprockets vs. Webpack/browserify • Disable Turbolinks • Concerns considered harmful • Rails API
99. sequel-rails From https://github.com/TalentBox/sequel-rails#using-sequel-rails
100. webpack with Rails From https://medium.com/brigade-engineering/setting-up-webpack-with-rails-c62aea149679
101. Turbolinks From http://blog.steveklabnik.com/posts/2013-06-25-removing-turbolinks-from-rails-4 However, keep in mind the code for handling Turbolinks still exists!
102. We could go on …
103. But something feels wrong
104. It’s good if you want to JUST use Rails.
105. But things become messy when you try to extend
106. Why not aim for something much simpler?
107. Don’t worry about bootstrapping speed! From “Simple Made Easy” at QCon London 2012 by Rich Hickey, http://www.infoq.com/presentations/Simple-Made-Easy-QCon-London-2012
108. Easiness doesn’t change, so let’s make our software simpler.
109. Lesscode • http://lesscode.is/ • Less Code track at RubyConf 2015
110. –Leonardo da Vinci “Simplicity is the ultimate sophistication.”