Rewriting Rack: A Functional Approach

RubyConf 2017

Transcript

1. Rewriting Rack A Functional Approach RubyConf 2017
2. Alex Wheeler @askwheeler github.com/alexwheeler
8. CALL 'Transfer' USING BY VALUE AMOUNT, BY REFERENCE SENDER, BY REFERENCE RECEIVER.
14. StandardError KeyError NameError EOFError
16. $! $@ $_ $$
18. require "English" $ERROR_INFO $ERROR_POSITION $LAST_READ_LINE $PID
19. [1,2,3].map { |x| x + 2 }
21. 10.times do puts “I promise to always use VIM” end
22. 100.class #=> Integer 0x1a.class #=> Integer nil.class #=> NilClass true.class #=> TrueClass 'foo'.class #=> String 0b11010.class #=> Integer 123.4.class #=> Float 1.234e2.class #=> Float
23. class Integer def +(n) self - n end end 3 + 1 => 2
28. simplify
29. programming is tough
30. we’re human
31. p = proc { |x| x + 1 }
32. p = proc { |x| x + 1 } p.call(1)
33. p = proc { |x| x + 1 } p.call(1) p[1]
34. p = proc { |x| x + 1 } p.call(1) p[1] p.(1)
35. p = proc { |x| x + 1 } p.call(1) p[1] p.(1) p.send(:call, 1)
36. p = proc { |x| x + 1 } p.call(1) p[1] p.(1) p.send(:call, 1) p.public_send(:call, 1)
37. p = proc { |x| x + 1 } p.call(1, 2, 3, 4, 5, 6) p[1, “msg”, :k] p.(1, :b, :c, “msg”) p.send(:call, 1, :x, :y, :z) p.public_send(:call, 1, 2, 3)
38. Functional Programming
39. • organizing code around functions instead of objects • avoid mutable data
40. simplify
42. “A change of perspective is worth 80 IQ points” - Alan Kay
54. class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end
55. require 'rack' class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end
56. require 'rack' class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end app = App.new
57. require 'rack' class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end app = App.new Rack::Handler::Unicorn
58. require 'rack' class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end app = App.new Rack::Handler::Unicorn.run(app)
59. require 'rack' class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end app = App.new Rack::Handler::Puma.run(app)
60. require 'rack' class App def call(env) ['200', {'Content-Type' => 'text/html'}, ['<p>Hi</p>']] end end app = App.new Rack::Handler::WEBrick.run(app)
62. require 'rack' app = proc{|env| [‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} Rack::Handler::WEBrick.run(app)
63. require 'rack' app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} Rack::Handler::WEBrick.run(app)
64. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]}
65. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new
66. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new builder.run(app)
67. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new builder.run(app) Rack::Handler::WEBrick.run(builder)
68. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new builder.use(Logger) builder.run(app) Rack::Handler::WEBrick.run(builder)
69. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new builder.use(Logger) builder.use(Cache) builder.run(app) Rack::Handler::WEBrick.run(builder)
70. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new builder.use(Logger) builder.use(Cache) builder.run(app) Rack::Handler::WEBrick.run(builder.to_app)
71. Middleware
75. class Middleware def call(env) end end
76. class Middleware def initialize(next_app) @next_app = next_app end def call(env) end end
77. class Middleware def initialize(next_app) @next_app = next_app end def call(env) # do something with env @next_app.call(env) end end
80. builder = Rack::Builder.new builder.use Logger builder.use Cache builder.run proc {|env| [200, {}, []] Rack::Handler::WEBrick.run builder.to_app
81. builder = Rack::Builder.new builder.use Logger builder.use Cache builder.run proc {|env| [200, {}, []] Rack::Handler::WEBrick.run builder.to_app
82. builder = Rack::Builder.new builder.use Logger builder.use Cache builder.run proc {|env| [200, {}, []] Rack::Handler::WEBrick.run builder.to_app
83. builder = Rack::Builder.new builder.use Logger builder.use Cache builder.run proc {|env| [200, {}, []] Rack::Handler::WEBrick.run builder.to_app
84. def initialize; end def use; end def run; end def to_app; end
85. def initialize(default_app = nil, &block) @use, @map, @run, @warmup, @freeze_app = [], nil, default_app, nil, false instance_eval(&block) if block_given? end def use(middleware, *args, &block) if @map mapping, @map = @map, nil @use << proc { |app| generate_map app, mapping } end @use << proc { |app| middleware.new(app, *args, &block) } end def run(app) @run = app end def call(env) to_app.call(env) end def to_app app = @map ? generate_map(@run, @map) : @run fail "missing run or map statement" unless app app.freeze if @freeze_app app = @use.reverse.inject(app) { |a,e| e[a].tap { |x| x.freeze if @freeze_app } } @warmup.call(app) if @warmup app end
86. def initialize() @use = [] end def use(middleware) @use << proc { |app| middleware.new(app) } end def run(app) @run = app end def to_app app = @run app = @use.reverse.inject(app) {|a,e| e[a]} app end
87. def to_app app = @run app = @use.reverse.inject(app) {|a,e| e[a]} app end
88. def to_app @use.reverse.reduce(app) do |stack, next_middleware| next_middleware.call(stack) end end
89. app = ->(env){[‘200’, {'Content-Type' => 'text/html'}, ['<p>Hi</p>']]} builder = Rack::Builder.new builder.use(Logger) builder.use(Cache) builder.run(app) Rack::Handler::WEBrick.run(builder.to_app)
90. builder.use(Logger) builder.use(Cache)
91. [ proc { |app| Logger.new(app) }, proc { |app| Cache.new(app) }, ]
92. [ proc { |app| Cache.new(app) }, proc { |app| Logger.new(app) }, ]
93. rack_app = proc { |env| [200, {}, []]} [ proc { |app| Cache.new(app) }, proc { |app| Logger.new(app) }, ]
94. rack_app = proc { |env| [200, {}, []]} [ Cache.new(rack_app), proc { |app| Logger.new(app) }, ]
95. [ Cache.new(rack_app), proc { |app| Logger.new(app) }, ]
96. [ Logger.new(Cache.new(rack_app)) ]
97. Logger.new(Cache.new(rack_app))
98. Logger.new( Cache.new(rack_app))
99. Logger.new( Cache.new( rack_app))
100. Logger.new( Cache.new( rack_app))
101. class Logger def initialize end end
102. class Logger def initialize end end proc { }
103. class Logger def initialize(app) @app = app end end proc { }
104. class Logger def initialize(app) @app = app end end proc {|app| }
105. class Logger def initialize(app) @app = app end def call end end proc {|app| }
106. class Logger def initialize(app) @app = app end def call end end proc do |app| proc {} end
107. class Logger def initialize(app) @app = app end def call(env) end end proc do |app| proc {} end
108. class Logger def initialize(app) @app = app end def call(env) end end proc do |app| proc {|env| } end
109. class Logger def initialize(app) @app = app end def call(env) @app.call(env) end end proc do |app| proc {|env| } end
110. class Logger def initialize(app) @app = app end def call(env) @app.call(env) end end proc do |app| proc {|env| app.call(env)} end
111. class Logger def initialize(app) @app = app end def call(env) @app.call(env) end end Logger = proc do |app| proc { |env| app.call(env) } end
112. class Logger def initialize(app) @app = app end def call(env) @app.call(env) end end Logger = ->(app) do ->(env){ app.call(env) } end
113. Logger = ->(app) do ->(env) do app.call(env) end end
114. Logger = ->(app) do ->(env) do app.call(env) end end Cache = ->(app) do ->(env) do app.call(env) end end
115. app = ->(req) do [200, {}, ["Hello"]] end Logger = ->(app) do ->(env) do app.call(env) end end Cache = ->(app) do ->(env) do app.call(env) end end
116. app = ->(req) do [200, {}, ["Hello"]] end Logger = ->(app) do ->(env) do app.call(env) end end Cache = ->(app) do ->(env) do app.call(env) end end builder = Cache.call(app)
117. app = ->(req) do [200, {}, ["Hello"]] end Logger = ->(app) do ->(env) do app.call(env) end end Cache = ->(app) do ->(env) do app.call(env) end end builder = Logger.call(Cache.call(app))
118. app = ->(req) do [200, {}, ["Hello"]] end Logger = ->(app) do ->(env) do app.call(env) end end Cache = ->(app) do ->(env) do app.call(env) end end builder = Logger.call(Cache.call(app)) Rack::Handler::WEBrick.run(builder)
119. app = ->(req) { [200, {}, ["Hello"]] } Logger = ->(app) { ->(env) { app.call(env) } } Cache = ->(app) { ->(env) { app.call(env) } } builder = Logger.call(Cache.call(app)) Rack::Handler::WEBrick.run(builder)
120. app = ->(req) { [200, {}, ["Hello"]] } Logger = ->(app) { ->(env) { app.(env) } } Cache = ->(app) { ->(env) { app.(env) } } builder = Logger.call(Cache.call(app)) Rack::Handler::WEBrick.run(builder)
121. (app = ->(req) { [200, {}, ["Hello"]] }) (Logger = ->(app) { ->(env) { (app.(env)) } }) (Cache = ->(app) { ->(env) { (app.(env)) } }) (builder = Logger.call(Cache.call(app))) Rack::Handler::WEBrick.run(builder)
122. (app = ->(req) { [200, {}, ["Hello"]]}) (Logger = ->(app) { (->(env) { (app.(env))})}) (Cache = ->(app) { (->(env) { (app.(env))})}) (Rack::Handler::WEBrick.run(Logger.(Cache.(app))))
123. (defn app [req] {:status 200 :headers {} :body ""}) (defn Logger [app] (fn [env] (app env))) (defn Cache [app] (fn [env] (app env))) (jetty/run-jetty (Logger(Cache app)) {:port 3000})
124. (Logger = ->(app) { (->(env) { (app.(env))})}) (Cache = ->(app) { (->(env) { (app.(env))})})
125. (Logger = ->(app) { (->(env) { (app.(env))})}) (Cache = ->(app) { (->(env) { (app.(env))})}) (defn Logger [app] (fn [env] (app env))) (defn Cache [app] (fn [env] (app env)))
126. • RUBY IS AN ACCEPTABLE LISP
130. “Code is a liability” - Karl Baum
131. • Shared mutable state • Functions instead of objects
132. Shared Mutable State
134. def call(env) env["verdict_message"] = verdict_message(env["verdict"]) @app.call(env) end
135. def call(env) env["verdict_message"] = verdict_message(env["verdict"]) @app.call(env) end private def verdict_message(verdict) end
136. def call(env) env["verdict_message"] = verdict_message(env["verdict"]) @app.call(env) end private def verdict_message(verdict) if verdict == "guilty" "is guilty" else "is not guilty" end end
137. def call(env) env["verdict_message"] = verdict_message(env["verdict"], env["name"]) @app.call(env) end private def verdict_message(verdict, name) if verdict == "guilty" "#{name} is guilty" else "#{name} is not guilty" end end
138. def call(env) env["verdict_message"] = verdict_message(env["verdict"], env["name"]) @app.call(env) end private def verdict_message(verdict, name) first_name = name.split(" ").first if verdict == "guilty" "#{first_name} is guilty" else "#{first_name} is not guilty" en end
139. def call(env) env["verdict_message"] = verdict_message(env["verdict"], env["name"]) @app.call(env) end private def verdict_message(verdict, name) first_name = name.split(" ").first if first_name == "Mr." || first_name == “Mrs." first_name = name.split(" ")[1] if verdict == "guilty" "#{first_name} is guilty" else "#{first_name} is not guilty" end else if verdict == "guilty" "#{first_name} is guilty" else "#{first_name} is not guilty" end end end
140. def call(env) @name = env["name"] env["verdict_message"] = verdict_message(env["verdict"], env["name"]) @app.call(env) end private def verdict_message(verdict, name) first_name = name.split(" ").first if first_name == "Mr." || first_name == “Mrs." first_name = name.split(" ")[1] if verdict == "guilty" "#{first_name} is guilty" else "#{first_name} is not guilty" end else if verdict == "guilty" "#{first_name} is guilty" else "#{first_name} is not guilty" end end end
141. def call(env) @name = env["name"] env["verdict_message"] = verdict_message(env["verdict"]) @app.call(env) end private def verdict_message(verdict) if verdict == "guilty" "#{name} is guilty" else "#{name} is not guilty" end end def name words = @name.split(" ") if words.first == "Mr." || "Mrs." || "Ms" words[1] else words[0] end end
147. def call(env) puts self.object_id @name = env["name"] env["verdict_message"] = verdict_message(env["verdict"]) @app.call(env) end
149. @name = env["name"]
151. def call(env) dup._call(env) end def _call(env) @name = env["name"] env["verdict_message"] = verdict_message(env["verdict"]) @app.call(env) end
153. builder = Rack::Builder.new builder.use Logger builder.use Cache builder.freeze_app
154. def freeze_app @freeze_app = true end def to_app app = @run app.freeze if @freeze_app app = @use.reverse.inject(app) { |a,e| e[a].tap { |x| x.freeze if @freeze_app } } app end
155. def freeze_app @freeze_app = true end def to_app app = @run app.freeze if @freeze_app app = @use.reverse.inject(app) { |a,e| e[a].tap { |x| x.freeze if @freeze_app } } app end
156. def freeze_app @freeze_app = true end def to_app app = @run app.freeze if @freeze_app app = @use.reverse.inject(app) { |a,e| e[a].tap { |x| x.freeze if @freeze_app } } app end
158. Functions instead of objects
159. Data noun factual information used as a basis for reasoning, discussion, or calculation
160. class Person attr_reader :name def initialize(name) @name = name end end
161. class Person attr_reader :name def initialize(name) @name = name end end class Company attr_reader :name def initialize(name) @name = name end end
162. person = Person.new("Alex") company = Company.new("VTS")
163. person = Person.new("Alex") company = Company.new("VTS") person.update_name(“Al")
164. person = Person.new("Alex") company = Company.new("VTS") person.update_name(“Al”) person.name
165. person = Person.new("Alex") company = Company.new("VTS") person.update_name(“Al") person.name => “Al”
166. person = Person.new("Alex") company = Company.new("VTS") person.update_name(“Al") person.name => “Al” company.update_name(“V")
167. NoMethodError: undefined method `update_name'
168. class Person def update_name(name) @name = name end end class Company def change_name(name) @name = name end end
169. class Person def update_name(name) @name = name end end class Company def change_name(name) @name = name end end
170. class Person def update_name(name) @name = name end end class Company def change_name(name) @name = name end end
171. (def person { :name "Alex" })
172. (def person { :name "Alex" }) (def company { :name "VTS" })
173. (def person { :name "Alex" }) (def company { :name "VTS" }) (assoc person :name “Al")
174. (def person { :name "Alex" }) (def company { :name "VTS" }) (assoc person :name “Al") => { :name “A1” }
175. (def person { :name "Alex" }) (def company { :name "VTS" }) (assoc person :name “Al") => { :name “A1” } (assoc company :name “V”) => { :name “V” }
176. Rack::Request “convenient interface to a Rack environment”
177. def call(env) request = Rack::Request.new(env) end
178. def call(env) request = Rack::Request.new(env) request.params["ssn"] = censor(request.params["ssn"]) @app.call(env) end private def censor(ssn) ssn .delete("-") .chars .slice(5..9) .unshift("xxx-xx-") .join end
179. censor("662-11-0034") => "xxx-xx-0034"
180. def call(env) request = Rack::Request.new(env) request.params["ssn"] = censor(request.params["ssn"]) @app.call(env) end
184. def call(env) request = Rack::Request.new(env) request.params["ssn"] = censor(request.params["ssn"]) @app.call(env) end
185. def call(env) request = Rack::Request.new(env) request.params["ssn"] = censor(request.params["ssn"]) @app.call(env) end def call(env) request = Rack::Request.new(env) request.update_param("ssn", censor(request.params["ssn"])) @app.call(env) end
186. Rack::Request.new(env)
187. Rack::Request.new(env)
188. Person.new
189. Person.new
190. Company.new
191. Company.new
192. { name: “Alex” }
193. { name: “VTS” }
199. Does OO solve all our problems?
200. no
201. Will FP solve all our problems?
202. probably not
203. most importantly
204. have fun
205. Thank you Alex Wheeler @askwheeler github.com/alexwheeler