The Fast Lane: Asynchronous Rails

Oh no! Computers are not doubling in speed every two years anymore! How can we make software run faster? You and your Rails app cannot just wait doing nothing, so join me to explore how we can leverage concurrency and parallelism concepts to enhance performance and scalability!

Transcript

1. The Fast Lane: Async Rails
2. Matheus Richard
4. I II III
6. What is Async?
7. Stuff running at the same time “ - You, possibly
8. Concurrency vs Parallelism
12. 󰗺 󰘁
13. 󰗺 󰘁 👾
14. 󰗺 󰘁 🎮 👾
15. Concurrency 󰗺 󰘁 🎮 👾 I'LL PLAY THIS LEVEL
16. Concurrency 󰗺 󰘁 🎮 👾 I'LL PLAY THIS ONE
17. 😇 🤝 😇
18. Cooperative Execution 😇 🤝 😇
19. 😈 😈
20. 😭 😈 🎮 👾 I'LL PLAY THEM ALL!
21. 󰗺 󰘁 🎮 👾 5 MINUTES EACH 󰥺
22. 󰗺 󰘁 🎮 👾 Preemptive Execution 5 MINUTES EACH 󰥺
23. They don't wanna play the same game
24. Concurrency 󰗺 󰘁 🎮 👾 󰗺 󰘁 🎮 ⚽ CONTEXT SWITCH
25. We don't like that! We want to play at the same time “ - Kids
26. We want independence! “ - Kids
27. Parallelism 󰗺 󰘁 🎮 🎮 🏈 ⚽
28. Parallelism 󰗺 󰘁 🎮 🎮 🏈 ⚽
29. Parallelism 󰗺 󰘁 🎮 🎮 👾 ⚽
30. Review time
33. CRuby Specific
35. Fibers 🪡 Threads 🧵
36. 🏠 Ractors 🏭 Processes
37. 🏠 Ractors 🏭 Processes Fibers 🪡 Threads 🧵
38. 🪡 Fibers
39. fiber = Fiber.new do "Hey, I'm a fiber!" end
40. fiber = Fiber.new do "Hey, I'm a fiber!" end puts fiber.resume # Hey, I'm a fiber!
41. boy = Fiber.new do puts "I'm playing stage 1" Fiber.yield puts "I'm playing stage 2" end end
42. boy = Fiber.new do puts "I'm playing stage 1" Fiber.yield puts "I'm playing stage 2" end end
43. boy = Fiber.new do puts "I'm playing stage 1" Fiber.yield puts "I'm playing stage 2" end end
44. boy = Fiber.new do puts "I'm playing stage 1" Fiber.yield puts "I'm playing stage 2" end end boy.resume # 󰗺 I'm playing stage 1
45. boy = Fiber.new do puts "I'm playing stage 1" Fiber.yield puts "I'm playing stage 2" end end boy.resume # 󰗺 I'm playing stage 1 boy.resume # 󰗺 I'm playing stage 2
46. 󰗺 󰘁
47. current_stage = 1 boy = Fiber.new do loop do puts "󰗺 I'm playing stage :{current_stage}" current_stage += 1 Fiber.yield end end
48. current_stage = 1 boy = Fiber.new do loop do puts "󰗺 I'm playing stage :{current_stage}" current_stage += 1 Fiber.yield end end
49. current_stage = 1 boy = Fiber.new do loop do puts "󰗺 I'm playing stage :{current_stage}" current_stage += 1 Fiber.yield end end
50. current_stage = 1 boy = Fiber.new do loop do puts "󰗺 I'm playing stage :{current_stage}" current_stage += 1 Fiber.yield end end
51. # ::. girl = Fiber.new do loop do puts "󰘁 I'm playing stage :{current_stage}" current_stage += 1 Fiber.yield end end
52. 5.times do boy.resume girl.resume end
53. 5.times do boy.resume girl.resume end # 󰗺 I'm playing stage 1 # 󰘁 I'm playing stage 2 # 󰗺 I'm playing stage 3 # 󰘁 I'm playing stage 4 # 󰗺 I'm playing stage 5 # 󰘁 I'm playing stage 6 # 󰗺 I'm playing stage 7 # 󰘁 I'm playing stage 8 # 󰗺 I'm playing stage 9 # 󰘁 I'm playing stage 10
54. 2.times do boy.resume girl.resume girl.resume girl.resume girl.resume end
55. 2.times do boy.resume girl.resume girl.resume girl.resume girl.resume end # 󰗺 I'm playing stage 1 # 󰘁 I'm playing stage 2 # 󰘁 I'm playing stage 3 # 󰘁 I'm playing stage 4 # 󰘁 I'm playing stage 5 # 󰗺 I'm playing stage 6 # 󰘁 I'm playing stage 7 # 󰘁 I'm playing stage 8 # 󰘁 I'm playing stage 9 # 󰘁 I'm playing stage 10
56. 󰥺 YOU are the scheduler
57. 🧵 Threads
58. thread = Thread.new do puts "Hey, I'm a thread!" end
59. thread = Thread.new do puts "Hey, I'm a thread!" end # threads start running # automatically
60. thread = Thread.new do puts "Hey, I'm a thread!" end thread.join # Hey, I'm a thread!
61. So what?
62. fibonacci(35) fibonacci(35)
63. fibonacci(35) # Runs in ~1s fibonacci(35) # Runs in ~1s
64. t1 = Thread.new do fibonacci(35) end t2 = Thread.new do fibonacci(35) end
65. t1 = Thread.new do fibonacci(35) # Runs in ~1s end t2 = Thread.new do fibonacci(35) # Runs in ~1s end
66. [t1, t2].each { |t| t.join } # Takes ~2 seconds to run
67. t1 Executing t2
68. t1 Executing t2
69. Threads don't run in parallel!
70. Threads switch automatically on I/O
72. t1 = Thread.new do fibonacci(35) end
73. t1 = Thread.new do sleep 1 end
74. [t1, t2].each { |t| t.join } # Takes ~1 second to run
75. t1 Executing t2 Time
76. t1 Executing t2 Time I/O
77. t1 = Thread.new do sleep 1 end
78. t1 = Thread.new do File.read("README.md") end
79. t1 = Thread.new do HTTP.get("example.com") end
80. t1 = Thread.new do DB.query("SELECT 1;") end
81. 󰵏 You have a babysitter
82. 󰗺 󰘁
83. 󰥺 YOU PLAY A STAGE… …THEN YOU RUN AROUND THE BLOCK
84. Thread.new do puts "󰗺 I'm playing stage :{current_stage} now!" current_stage += 1 end
85. Thread.new do puts "󰗺 I'm playing stage :{current_stage} now!" current_stage += 1 sleep 1 end
86. boy Playing Running girl Time
87. boy girl Time Playing Running
88. current_stage = 1 5.times do [ Thread.new do ... end, Thread.new do ... end ].each(&:join) end
89. current_stage = 1 5.times do [ Thread.new do ... end, Thread.new do ... end ].each(&:join) end
90. 5.018222999991849 seconds to run
91. 1 second Executing I/O
92. girl Time 1 second Executing I/O 1 second . j o i n boy 1 second 1 second . j o i n ...
93. Threads are great!
94. Threads are great! Right…?
95. 󰗺 I'm playing stage 1 now! 󰘁 I'm playing stage 1 now! 󰗺 I'm playing stage 3 now! 󰘁 I'm playing stage 3 now! 󰗺 I'm playing stage 5 now! 󰘁 I'm playing stage 5 now! 󰗺 I'm playing stage 7 now! 󰘁 I'm playing stage 7 now! 󰗺 I'm playing stage 9 now! 󰘁 I'm playing stage 9 now!
96. Thread.new do puts "󰗺 I'm playing stage :{current_stage} now!" current_stage += 1 sleep 1 end
97. Thread.new do puts "󰗺 I'm playing stage :{current_stage} now!" current_stage += 1 sleep 1 end
98. current_stage = 1 mutex = Thread::Mutex.new
99. Thread.new do mutex.synchronize do puts "󰘁 I'm playing stage :{current_stage} now!" current_stage += 1 end sleep 1 end
100. Thread.new do mutex.synchronize do puts "󰘁 I'm playing stage :{current_stage} now!" current_stage += 1 end sleep 1 end
101. Thread.new do mutex.synchronize do puts "󰘁 I'm playing stage :{current_stage} now!" current_stage += 1 end sleep 1 end
102. Thread.new do mutex.synchronize do puts "󰘁 I'm playing stage :{current_stage} now!" current_stage += 1 end sleep 1 end
103. 󰗺 I'm playing stage 1 now! 󰘁 I'm playing stage 2 now! 󰗺 I'm playing stage 3 now! 󰘁 I'm playing stage 4 now! 󰗺 I'm playing stage 5 now! 󰘁 I'm playing stage 6 now! 󰗺 I'm playing stage 7 now! 󰘁 I'm playing stage 8 now! 󰗺 I'm playing stage 9 now! 󰘁 I'm playing stage 10 now! 5.014558000024408 seconds to run
104. Threads are hard
105. Shared mutable state is bad
106. 🏠 Ractors
107. current_stage = 1 Ractor.new do puts "󰗺 I'm playing stage :{current_stage}" end.take
108. current_stage = 1 Ractor.new do puts "󰗺 I'm playing stage :{current_stage}" end.take # raises ArgumentError
109. STAGE = "Foo" Ractor.new do puts "󰗺 I'm playing stage :{STAGE}" end.take # raises Ractor.:IsolationError
110. STAGE = "Foo".freeze Ractor.new do puts "󰗺 I'm playing stage :{STAGE}" end.take # I'm playing stage Foo
111. current_stage = 1 Ractor.new(current_stage) do |stage| puts "󰗺 I'm playing stage :{stage}" end.take # I'm playing stage 1
112. current_stage = 1 Ractor.new(current_stage) do |stage| puts "󰗺 I'm playing stage :{stage}" end.take # I'm playing stage 1
115. 󰗺 🎮 👾 󰘁 🎮 👾
117. 🏭 Processes
118. stage = Stage.new kid_1 = Process.fork do 5.times do puts "󰗺 I'm playing a stage :{stage}" end end
119. stage = Stage.new kid_1 = Process.fork do 5.times do puts "󰗺 I'm playing a stage :{stage}" end end
120. 󰗺 󰘁
121. 🏠 🏠 󰗺 󰘁
122. 🏠 󰥺󰸩 🏠 󰥺󰸩 󰗺 󰘁
123. 🏠 󰥺󰸩 󰗺 🏠 󰥺󰸩 󰘁
127. Concurrent Parallel
128. Concurrent Parallel Light Heavy Easy Hard
129. Concurrent Parallel Light Heavy Fibers 🪡 Easy Hard
130. Fibers Threads Ractors Processes Concurrent Parallel Light Heavy 🪡 🧵 Easy Hard
131. Concurrent Parallel Light Heavy Fibers Threads Ractors 🪡 🧵 🏠 Easy Hard
132. Concurrent Parallel Light Heavy Fibers Threads Ractors Processes 🪡 🧵 🏠 🏭 Easy Hard
133. Fiber::Scheduler
134. Async gem
135. Concurrent Parallel Light Heavy Fibers Threads Ractors Processes 🪡 🧵 🏠 🏭 Easy Hard
136. Concurrent Parallel Easy Hard 🪡 Fibers Threads Ractors Processes 🏠 🏭 🧵
138. Code
139. Principles
140. Don't do tomorrow what you can do today
141. Don't do tomorrow what you can do today Don't do tomorrow what you can do today 🚫
142. Don't do now what you can do later
143. class RegistrationsController def create @registration = Registration.new(params) if @registration.save RegistrationMailer .welcome_email(@registration) .deliver_now redirect_to @registration end # ... end
144. class RegistrationsController def create @registration = Registration.new(params) if @registration.save RegistrationMailer .welcome_email(@registration) .deliver_now redirect_to @registration end # ... end
145. class RegistrationsController def create @registration = Registration.new(params) if @registration.save RegistrationMailer .welcome_email(@registration) .deliver_now redirect_to @registration end # ... end
146. class RegistrationsController def create @registration = Registration.new(params) if @registration.save RegistrationMailer .welcome_email(@registration) .deliver_later redirect_to @registration end # ... end
147. class RegistrationsController def create @registration = Registration.new(params) if @registration.save RegistrationMailer .welcome_email(@registration) .deliver_later redirect_to @registration end # ... end
148. class RegistrationsController def create @registration = Registration.new(params) if @registration.save CollectRegistrationStatsJob .perform_later(@registration) redirect_to @registration end # ... end
149. class RegistrationsController def create @registration = Registration.new(params) if @registration.save ProcessProfilePictureJob .perform_later(@registration) redirect_to @registration end # ... end
150. class User < ApplicationRecord has_one_attached :avatar def delete_avatar avatar.purge end end
151. class User < ApplicationRecord has_one_attached :avatar def delete_avatar avatar.purge end end
152. class User < ApplicationRecord has_one_attached :avatar def delete_avatar_later avatar.purge_later end end
153. class Team < ApplicationRecord has_many :players, dependent: :destroy end class Player < ApplicationRecord belongs_to :team end
154. class Team < ApplicationRecord has_many :players, dependent: :destroy end class Player < ApplicationRecord belongs_to :team end
155. Team.destroy_by(name: "Flamengo")
156. Team.destroy_by(name: "Flamengo") # DELETE FROM "players" WHERE "players"."id" = 1 # DELETE FROM "players" WHERE "players"."id" = 2 # ... # DELETE FROM "players" WHERE "players"."id" = 11 # DELETE FROM "teams" WHERE "teams"."id" = 1
157. class Team < ApplicationRecord has_many :players, dependent: :destroy end class Player < ApplicationRecord belongs_to :team end
158. class Team < ApplicationRecord has_many :players, dependent: :destroy_async end class Player < ApplicationRecord belongs_to :team end
159. Team.destroy_by(name: "Flamengo")
160. Team.destroy_by(name: "Flamengo") # Enqueued ActiveRecord::DestroyAssociationAsyncJob
161. Don't do now what you can do later
162. But…
163. Don't stand still
164. Time tasks Executing I/O
165. Time Executing I/O tasks
166. HTTP Requests
167. class TwitterNewsletter def initialize(tweets) @tweets = tweets end def to_s # ... end end
168. def to_s @tweets .map { |tweet| summary_for(tweet) } .join("\n") end
169. def summary_for(tweet) AI.ask("Write a summary for this tweet: :{tweet}") end
170. module AI def self.ask(question) HTTP.post(URL, question) end end
171. module AI def self.ask(question) sleep(1) end end
172. tweets = [ "I'm learning Ruby", "I'm learning Rails" ] time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 2.011646999977529 seconds to run
173. tweets = [ "I'm learning Ruby", "I'm learning Rails" ] time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 2.011646999977529 seconds to run
174. tweets = [ "I'm learning Ruby", "I'm learning Rails" ] time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 2.011646999977529 seconds to run
175. Time requests Executing I/O
176. class TwitterNewsletter def to_s @tweets .map { |tweet| summary_for(tweet) } .join("\n") end end
177. def to_s Sync do @tweets .map { |tweet| Async { summary_for(tweet) } } .map(&:wait) .join("\n") end end
178. def to_s Sync do @tweets .map { |tweet| Async { summary_for(tweet) } } .map(&:wait) .join("\n") end end
179. def to_s Sync do @tweets .map { |tweet| Async { summary_for(tweet) } } .map(&:wait) .join("\n") end end
180. def to_s Sync do @tweets .map { |tweet| Async { summary_for(tweet) } } .map(&:wait) .join("\n") end end
181. def to_s Sync do @tweets .map { |tweet| Async { summary_for(tweet) } } .map(&:wait) .join("\n") end end
182. tweets = [ "I'm learning Ruby", "I'm learning Rails" ] time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 1.011646999977529 seconds to run
183. tweets = [ "I'm learning Ruby", "I'm learning Rails" ] time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 1.011646999977529 seconds to run
184. Time Executing I/O requests
185. tweets = [ "I'm learning Ruby", "I'm learning Rails" ] time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 1.011646999977529 seconds to run
186. tweets = Array.new(1_000) do "Tweet :{_1}" end time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 1.011646999977529 seconds to run
187. tweets = Array.new(1_000) do "Tweet :{_1}" end time = Benchmark.measure do puts TwitterNewsletter.new(tweets) end puts ":{time.real} seconds to run" # 1.011646999977529 seconds to run
189. DB Queries
190. class ReportsController def create @new_authors = Author.recent @new_books = Book.recent @new_reviews = BookReview.recent end end
191. class Book < ActiveRecord::Base belongs_to :author scope :recent, :> { where("select true from pg_sleep(1)").limit(1) } end
192. Author Load (1002.0ms) Book Load (1001.5ms) BookReview Load (1001.7ms)
193. 3 seconds
194. ActiveRecord::Relation#load_async
195. Time Executing I/O queries
196. class ReportsController def create @new_authors = Author.recent @new_books = Book.recent @new_reviews = BookReview.recent end end
197. class ReportsController def create @new_authors = Author.recent.load_async @new_books = Book.recent.load_async @new_reviews = BookReview.recent.load_async end end
198. ASYNC Author Load (1010.2ms) (db time 1011.4ms) ASYNC Book Load (2.2ms) (db time 1013.8ms) ASYNC BookReview Load (0.2ms) (db time 1014.7ms)
199. ASYNC Author Load (1010.2ms) (db time 1011.4ms) ASYNC Book Load (2.2ms) (db time 1013.8ms) ASYNC BookReview Load (0.2ms) (db time 1014.7ms)
200. ASYNC Author Load (1010.2ms) (db time 1011.4ms) ASYNC Book Load (2.2ms) (db time 1013.8ms) ASYNC BookReview Load (0.2ms) (db time 1014.7ms)
201. ASYNC Author Load (1010.2ms) (db time 1011.4ms) ASYNC Book Load (2.2ms) (db time 1013.8ms) ASYNC BookReview Load (0.2ms) (db time 1014.7ms)
202. 1 second
203. 3x Faster
206. Thread Pool
207. default: &default adapter: postgresql pool: 5
208. 🎮 🎮 🎮
209. 󰗺 󰘁 󰪌 🎮 🎮 🎮
210. 󰘁 🎮🎮🎮
211. 󰘁 🎮🎮🎮 󰗺 󰪌 WE WANT TO PLAY TOO
212. 󰘁 🎮🎮🎮 😡 🤬 WAIT LOL
213. Be careful with busy routes
214. class BooksController def show @new_books = Book.recent.load_async @external_books = HTTP.get( "https::/external.com/books" ) end end
215. Lazy Loading Lazy Loading
216. Async Views Async Views
218. class DashboardController def show @best_sellers = Book.best_sellers @top_reviewed_books = Book.top_reviewed # ... end end
219. class DashboardController def show @best_sellers = Book.best_sellers # takes 10 seconds @top_reviewed_books = Book.top_reviewed # ... end end
220. class DashboardController def show @best_sellers = Book.best_sellers.load_async @top_reviewed_books = Book.top_reviewed.load_async # ... end end
221. Lazy-loaded Turbo Frames
222. <div id="top_reviewed"> Dashboard <turbo-frame id="best_sellers" src="::.">
223. <div id="top_reviewed"> Dashboard <turbo-frame id="best_sellers" src="::.">
224. Dashboard BestSellers <div id="top_reviewed"> <turbo-frame id="best_sellers" src="::."> <turbo-frame id="best_sellers">
225. Dashboard BestSellers <div id="top_reviewed"> <turbo-frame id="best_sellers"> <turbo-frame id="best_sellers" src="::.">
226. Dashboard <div id="top_reviewed"> BestSellers <div id="top_reviewed"> <turbo-frame id="best_sellers">
227. Dashboard <div id="top_reviewed"> <turbo-frame id="best_sellers"> <turbo-frame id="best_sellers"> <div id="top_reviewed">
228. <div class="dashboard"> <div id="best_sellers"> :::- ... → :/div> <div id="top_reviewed">:::- ... ::>:/div> :/div>
229. <div class="dashboard"> <turbo-frame id="best_sellers" src="books/best_sellers" loading="lazy" >:/turbo-frame> <div id="top_reviewed">:::- ... ::>:/div> :/div>
230. <div class="dashboard"> <turbo-frame id="best_sellers" src="books/best_sellers" loading="lazy" >:/turbo-frame> <div id="top_reviewed">:::- ... ::>:/div> :/div>
231. <div class="dashboard"> <turbo-frame id="best_sellers" src="books/best_sellers" loading="lazy" >:/turbo-frame> <div id="top_reviewed">:::- ... ::>:/div> :/div>
232. <div class="dashboard"> <turbo-frame id="best_sellers" src="books/best_sellers" loading="lazy" >:/turbo-frame> <div id="top_reviewed">:::- ... ::>:/div> :/div>
233. class Books::BestSellersController def index @best_sellers = Book.best_sellers # takes 10 seconds end end
234. <turbo-frame id="best_sellers"> <h1>Best Sellers:/h1> <% @best_sellers.each do |book| %> <%# ... %> <% end %> :/turbo-frame>
235. <div id="top_reviewed"> Dashboard <turbo-frame id="best_sellers" src="::.">
236. <div id="top_reviewed"> Dashboard <turbo-frame id="best_sellers" src="::.">
237. <div id="top_reviewed"> Dashboard <turbo-frame id="best_sellers" src="::."> <turbo-frame id="best_sellers"> BestSellers
238. Dashboard BestSellers <div id="top_reviewed"> <turbo-frame id="best_sellers" src="::."> <turbo-frame id="best_sellers">
239. Dashboard BestSellers <div id="top_reviewed"> <turbo-frame id="best_sellers"> <turbo-frame id="best_sellers" src="::.">
240. Dashboard <div id="top_reviewed"> BestSellers <div id="top_reviewed"> <turbo-frame id="best_sellers">
241. Dashboard <div id="top_reviewed"> <turbo-frame id="best_sellers"> <turbo-frame id="best_sellers"> <div id="top_reviewed">
242. ⏳
243. just some random text here. This is not import nore itant so i
244. just some random text here. This is not import nore itant so i just some random text here. This is not important so ignore it ⏳
245. Principles
246. <script async src="async-script.js">
247. <link rel="stylesheet" href="critical.css"> <link rel="stylesheet" href="non-critical.css" media="print" onload=" this.onload=null; this.removeAttribute('media'); ">
248. <link rel="stylesheet" href="critical.css"> <link rel="stylesheet" href="non-critical.css" media="print" onload=" this.onload=null; this.removeAttribute('media'); ">
249. @font-face { font-family: "My Font"; font-style: normal; font-weight: 400; font-display: swap; src: font-url("my-font.ttf"); }
250. @font-face { font-family: "My Font"; font-style: normal; font-weight: 400; font-display: swap; src: font-url("my-font.ttf"); }
251. Rafael França rules! Lorem ipsum, dolor sit amet consectetur adipisicing elit. Rem sint nisi, dolorem accusantium fugiat, eligendi temporibus voluptatum est.
252. Rafael França rules! Lorem ipsum, dolor sit amet consectetur adipisicing elit. Rem sint nisi, dolorem accusantium fugiat, eligendi temporibus voluptatum est.
253. <img loading="lazy" src="image.jpg" :>
256. Rails .application .config .action_view .image_loading = "lazy"
257. just some random text here. This is not import nore itant so i
259. Async Dev Tools
261. Adapted from xkcd
262. class AddIndexToUserRoles < ActiveRecord::Migration disable_ddl_transaction! def change add_index :users, :role, algorithm: :concurrently end end
263. class AddIndexToUserRoles < ActiveRecord::Migration disable_ddl_transaction! def change add_index :users, :role, algorithm: :concurrently end end
264. Parallel Tests
265. class ActiveSupport::TestCase parallelize(workers: 2) end
266. class ActiveSupport::TestCase parallelize( workers: :number_of_processors ) end
267. | Workers | Test Suite Time | |---------|-----------------| | 1 | 40 min | | 2 | 20 min | | 4 | 10 min |
269. parallel_tests gem
270. All Roses
271. Pitfalls
272. With great power…
273. Async
279. class IndexUsersOnEmail < ActiveRecord::Migration def change add_index :users, :email, unique: true end end
280. class BooksController < ApplicationController def index @books = Book.published.includes(:authors) end end
281. <% books.each do |book| %> <% cache(book) do %> <%= render book %> <% end %> <% end %>
282. class RolesController < ApplicationController def index Rails.cache.fetch("roles", expires_in: 1.hour) do Auth0::Roles.fetch_all end end end
283. user_roles = users.map do |user| user.roles end.flatten
284. user_roles = users.flat_map do |user| user.roles end
285. rubocop-performance
286. def fibonacci(n) if n < 2 n else fibonacci(n - 1) + fibonacci(n - 2) end end
290. @MatheusRich
291. Questions.ask_now @MatheusRich | www.matheusrich.com | thoughtbot
292. Questions.ask_later @MatheusRich | www.matheusrich.com | thoughtbot