But At What Cost?

Building a template processor for Rails.

Transcript

1. Hello!
2. doES iT sCaLe?
3. Jubilee Year
4. Look at all the things I’m NOT doing!
5. Prologue
7. Ruby Script
9. But At What Cost?
10. Aaron Patterson
11. Live From Here
19. I have stickers of my cat! (please say "hello")
20. @tenderlove
23. Other == Puns?
24. Speaking of Twitter…
25. "
30. @buritica
31. ~54% useless
32. March 14, 2019
35. "But At What Cost?" Bot
36. Twitter: 100% Useless
37. Facepalm-er
38. Facepalm-ee
39. Response Algorithm Is it a pun? "Aaron" "But At What Cost?" Yes No
40. Let’s Practice
41. G GitHub
42. Active Job
44. G GitHub We’re Hiring!!!!
47. http://git.io/sparkles
48. Ruby Core Team
49. 10 Years On Ruby Core! W ow !!!
50. Rails Core Team
52. I ❤ Ruby
54. Just Worked™
55. No Boilerplate
56. Java (1.3?) vs Ruby List list = new ArrayList(); list.add("1"); list.add("2"); list.add("3"); Iterator iter = list.iterator(); List intList = new ArrayList(); while (iter.hasNext()) { String str = (String)iter.next(); intList.add(Integer.parseInt(str)); } list = %w{ 1 2 3 } intList = list.map { |l| l.to_i } Java Ruby
57. My First Ruby Program Serious ^
58. Never Write Infinite Loops
59. I ❤ Rails
61. Just Worked™
62. No Boilerplate
63. Community Values
64. "I MUST WRITE RAILS!"
65. BUT AT WHAT COST?
66. -25% $114k ➡ $85k (in 2006)
67. More Companies
68. More People
69. Thank You!
70. #ENDGAME
72. BUT AT WHAT COST?
74. Game of Thrones
75. Dumbledore Dies
77. Cool Performance Tips
78. No Parenthesis is Faster
79. Parens vs No Parens def foo1(bar, baz) end def foo2(bar, baz) end def foo3(bar, baz) end def foo1 bar, baz end def foo2 bar, baz end def foo3 bar, baz end Parens No Parens
80. "No code is faster than no code"
81. ruby -y
82. Parse States $ ruby --disable-gems -y with-parens.rb | wc -l 805 $ ruby --disable-gems -y without-parens.rb | wc -l 778
83. Single Quotes Are 2x Faster Than Double Quotes
84. You Have To Hit The Shift Key To Type "
85. Actual Performance Tip Rails 6!
86. Allocation Count Started GET "/users/new" for ::1 at 2019-04-30 16:45:49 -0500 Processing by UsersController#new as */* Rendering users/new.html.erb within layouts/application Rendered users/_form.html.erb (Duration: 1.4ms | Allocations: 552) Rendered users/new.html.erb within layouts/application (Duration: 1.7ms | Allocations: 640) Completed 200 OK in 6ms (Views: 5.4ms | ActiveRecord: 0.0ms | Allocations: 4140) Started GET "/users/new" for ::1 at 2019-04-30 16:47:02 -0500 Processing by UsersController#new as */* Rendering users/new.html.erb within layouts/application Rendered users/_form.html.erb (Duration: 1.4ms | Allocations: 827) Rendered users/_expensive.html.erb (Duration: 1.6ms | Allocations: 10098) Rendered users/new.html.erb within layouts/application (Duration: 4.3ms | Allocations: 11553) Completed 200 OK in 9ms (Views: 8.5ms | ActiveRecord: 0.0ms | Allocations: 15981)
87. Allocation Count Started GET "/users/new" for ::1 at 2019-04-30 16:45:49 -0500 Processing by UsersController#new as */* Rendering users/new.html.erb within layouts/application Rendered users/_form.html.erb (Duration: 1.4ms | Allocations: 552) Rendered users/new.html.erb within layouts/application (Duration: 1.7ms | Allocations: 640) Completed 200 OK in 6ms (Views: 5.4ms | ActiveRecord: 0.0ms | Allocations: 4140) Started GET "/users/new" for ::1 at 2019-04-30 16:47:02 -0500 Processing by UsersController#new as */* Rendering users/new.html.erb within layouts/application Rendered users/_form.html.erb (Duration: 1.4ms | Allocations: 827) Rendered users/_expensive.html.erb (Duration: 1.6ms | Allocations: 10098) Rendered users/new.html.erb within layouts/application (Duration: 4.3ms | Allocations: 11553) Completed 200 OK in 9ms (Views: 8.5ms | ActiveRecord: 0.0ms | Allocations: 15981)
88. Rails at GitHub
89. Template Pre-Compilation Method Name Generation
90. Template Pre- Compilation
91. Method Name Generation
92. Build a Template Renderer!
93. Rails is MVC
94. MVC Model View Controller Request
95. Modal View Controller
96. MVC Model View Controller Request Action Controller Action View Active Record
97. Action View
98. Action View Finds Templates Compiles Templates Executes Views
99. View Templates
100. ERB
101. Developed by @m_seki
102. ERB Template <h1>New User</h1> <%= render_form %> <%= link_to 'Back' %> new.html.erb
103. ERB Compiler require "erb" # Compile the template template = ERB.new File.read "test.html.erb" # Print the template source puts template.src # Evaluate the template puts template.result(binding) compile.rb
104. Compiled Template _erbout = +"" _erbout << "<h1>New User</h1>\n\n".freeze _erbout << render_form.to_s _erbout << "\n\n".freeze _erbout << link_to("Back").to_s _erbout << "\n".freeze _erbout
105. Modified Compile Script require "erb" def render_form "<form></form>" end def link_to(text) "<a href=\"#\">#{text}</a>" end # Compile the template template = ERB.new File.read "test.html.erb" # Evaluate the template puts template.result(binding)
106. Compiler Output $ ruby compiler.rb <h1>New User</h1> <form></form> <a href="#">Back</a>
107. ERB Translations ERB Source Translated Ruby <%= something %> _erbout << something.to_s <% something_else %> something_else
108. Capturing Blocks <div> <%= capture do %> Hello! <% end %> </div> require "erb" def capture yield end # Compile the template template = ERB.new File.read "test.html.erb" puts template.result(binding)
109. What is the output? Hello! <div> </div> <div> Hello! </div> ERROR!
110. Compiled Source _erbout = +'' _erbout << "<div>\n ".freeze _erbout << ( capture do ).to_s _erbout << "\n Hello!\n ".freeze end _erbout << "\n</div>\n".freeze _erbout <div> <%= capture do %> Hello! <% end %> </div>
111. Compiled Source _erbout = +'' _erbout << "<div>\n ".freeze _erbout << ( capture do ).to_s _erbout << "\n Hello!\n ".freeze end _erbout << "\n</div>\n".freeze _erbout <div> <%= capture do %> Hello! <% end %> </div>
112. How does this work in Rails?
113. ERB Compiler BLOCK_EXPR = /\s*((\s+|\))do|\{)(\s*\|[^|]*\|)?\s*\Z/ def add_expression(indicator, code) flush_newline_if_pending(src) if (indicator == "==") || @escape src << "@output_buffer.safe_expr_append=" else src << "@output_buffer.append=" end if BLOCK_EXPR.match?(code) src << " " << code else src << "(" << code << ");" end end
114. ERB in Rails
115. Different ERB Flavors Original ERB ERubis ERubi
116. ERB Performance
117. Rendering Speed require "erb" require "benchmark/ips" class AaronView TEMPLATES = { } TEMPLATES["index"] = <<-eerb <html> <body> <h1>Hello <%= name %><h1> </html> eerb def name; "Aaron"; end def render(template) ERB.new(TEMPLATES[template]).result(binding) end end view = AaronView.new Benchmark.ips do |x| x.report("render") { view.render("index") } end
118. Rendering Speed $ ruby rendering_speed.rb Warming up -------------------------------------- render 2.696k i/100ms Calculating ------------------------------------- render 27.117k (± 5.9%) i/s - 137.496k in 5.092633s
119. Cache Compilation class AaronView TEMPLATES = { } TEMPLATES["index"] = <<-eerb <html> <body> <h1>Hello <%= name %><h1> </html> eerb def name; "Aaron"; end def render(template) ERB.new(TEMPLATES[template]).result(binding) end COMPILED_TEMPLATES = { } def render_compiled(template) erb = COMPILED_TEMPLATES[template] ||= ERB.new(TEMPLATES[template]) erb.result(binding) end end view = AaronView.new Benchmark.ips do |x| x.report("render") { view.render("index") } x.report("render compiled") { view.render_compiled("index") } x.compare! end
120. Cache Compilation $ ruby rendering_speed.rb Warming up -------------------------------------- render 2.709k i/100ms render compiled 6.293k i/100ms Calculating ------------------------------------- render 27.115k (± 2.6%) i/s - 138.159k in 5.098881s render compiled 63.645k (± 3.9%) i/s - 320.943k in 5.050544s Comparison: render compiled: 63645.5 i/s render: 27114.8 i/s - 2.35x slower
121. Define a Method class AaronView TEMPLATES = { } TEMPLATES["index"] = <<-eerb <html> <body> <h1>Hello <%= name %><h1> </html> eerb def name; "Aaron"; end def render(template) ERB.new(TEMPLATES[template]).result(binding) end COMPILED_TEMPLATES = { } def render_compiled(template) erb = COMPILED_TEMPLATES[template] ||= ERB.new(TEMPLATES[template]) erb.result(binding) end METHODS_DEFINED = { } def render_with_method(template) unless METHODS_DEFINED.key? template erb = ERB.new(TEMPLATES[template]) self.class.class_eval "def render_#{template}; #{erb.src}; end" METHODS_DEFINED[template] = true end send "render_#{template}" end end
122. Define a Method $ ruby rendering_speed.rb Warming up -------------------------------------- render 2.750k i/100ms render compiled 6.462k i/100ms render method 114.420k i/100ms Calculating ------------------------------------- render 28.389k (± 2.7%) i/s - 143.000k in 5.041158s render compiled 65.860k (± 2.4%) i/s - 329.562k in 5.006962s render method 1.477M (± 1.7%) i/s - 7.437M in 5.038304s Comparison: render method: 1476591.3 i/s render compiled: 65860.1 i/s - 22.42x slower render: 28388.6 i/s - 52.01x slower
123. Method Generation require "erb" erb_source = <<-erb <html> <body> <h1>Hello <%= name %><h1> </html> erb erb = ERB.new erb_source template = "index" self.class.class_eval "def render_#{template}; #{erb.src}; end" send "render_#{template}" Template Source Compile Source Define a m ethod Render the Template
124. Method Generation def render_index _erbout = +'' _erbout << "<html>\n <body>\n <h1>Hello ".freeze _erbout << name.to_s _erbout << "<h1>\n</html>\n".freeze _erbout end Compiled Source
125. Templates Are Translated to Methods
126. Rails Template Methods <h1> This is an inner template <% puts methods.grep(/_app/) %> </h1> Template in Rails
127. Rails Template Methods Console Output _app_views_users_index_html_erb___4485674087862414886_70282093274980 _app_views_users__first_ja_html_erb__657974686689484881_70282053324000 _app_views_users__second_html_erb___3508242123539422948_70282053523460
128. Memory Size def render_index _erbout = +'' _erbout << "<html>\n <body>\n <h1>Hello ".freeze _erbout << name.to_s _erbout << "<h1>\n</html>\n".freeze _erbout end require "objspace" iseq = RubyVM::InstructionSequence.of( method(:render_index)) p ObjectSpace.memsize_of iseq $ ruby test.rb 1264
129. Template Handling In Rails
130. Instance Variable Visibility <h1>This is template Foo!</h1> <%= @some_ivar %> <h1>This is template Bar!</h1> <%= @some_ivar %> _foo.html.erb _bar.html.erb
131. Compiled Templates class ActionView::Base def render_foo _erbout = +'' _erbout << "<h1>This is template Foo!</h1>\n".freeze _erbout << @some_ivar.to_s _erbout << "\n".freeze _erbout end def render_bar _erbout = +'' _erbout << "<h1>This is template Barr!</h1>\n".freeze _erbout << @some_ivar.to_s _erbout << "\n".freeze _erbout end end _foo.html.erb _bar.html.erb Same Instance Same Instance
132. Don’t use instance variables in your templates
133. "Don’t use instance variables in your templates" - Aaron
134. Instance Variable Visibility <h1>This is template Foo!</h1> <%= @some_ivar %> <h1>This is template Bar!</h1> <%= @some_ivar %> _foo.html.erb _bar.html.erb
135. Local Variables
136. Rendering With Locals <body> <%= render "content", locals: { name: "Gorby" } %> </body>
137. Compiling With Locals <h1> Hello, <%= name %> </h1> def render_content _erbout = +'' _erbout << "<h1>\n Hello, ".freeze _erbout << name.to_s _erbout << "\n</h1>\n".freeze _erbout end content.html.erb Compiled Method Method Call
138. Preamble With Locals
139. Compiling With Locals <h1> Hello, <%= name %> </h1> def render_content(locals) # Locals preamble name = locals[:name] _erbout = +'' _erbout << "<h1>\n Hello, ".freeze _erbout << name.to_s _erbout << "\n</h1>\n".freeze _erbout end content.html.erb Compiled Method
140. Templates Require Context <body> <%= render "content", locals: { name: "Gorby" } %> <%= render "content" %> </body> <h1> Hello, <%= name %> </h1> main.html.erb content.html.erb Method call or local variable? local variable method call
141. Templates Can’t Be Compiled In Advance* *(FORESHADOWING)
142. Compiled Too Many Times
143. Too Many Compilations <body> <%= render "content", locals: { name: "Gorby" } %> <%= render "content", locals: { name: "Gorby", friend: "Aaron" } %> </body> def render_content_1(locals) # Locals preamble name = locals[:name] _erbout = +'' _erbout << "<h1>\n Hello, ".freeze _erbout << name.to_s _erbout << "\n</h1>\n".freeze _erbout end def render_content_2(locals) # Locals preamble name = locals[:name] friend = locals[:friend] _erbout = +'' _erbout << "<h1>\n Hello, ".freeze _erbout << name.to_s _erbout << "\n</h1>\n".freeze _erbout end main.html.erb Compiled "content" Unique Preambles
144. "This is nice, but what should I do?"
145. Always pass the same locals to individual templates.
146. The render function
147. Finds a Template Compiles the Template Calculates a Method Name Calls the Method
148. Find a Template (from the cache) Compiled? Compile the Template Call the method Calculate a Method Name
149. Finding a Template
150. Template Rendering Depends on "Requested Format"
151. Users Controller class UsersController < ApplicationController # GET /users # GET /users.json def index @users = User.all render "index" end end $ tree app/views/users app/views/users !"" index.html.erb #"" index.xml.erb Controller app/views/users/*
152. Template Source <h1>XML template</h1> <h1>Users</h1> index.xml.erb index.html.erb
153. Requests and Rendering Request Response Template Rendered curl -H 'Accept: application/xml' http:// localhost:3000/users <h1>XML template</h1> index.xml.erb curl http://localhost: 3000/users <h1>Users</h1> index.html.erb curl -H 'Accept: text/ html' http://localhost: 3000/users <h1>Users</h1> index.html.erb
154. Template Cache Keys • Local variables • Format • Locale • Variant (iPhone, etc)
155. Strange Render Behavior
156. Users Controller class UsersController < ApplicationController # GET /users # GET /users.json def index @users = User.all render "index" end end $ tree app/views/users app/views/users !"" _my_template.png.erb !"" _my_template.xml.erb #"" index.html.erb Controller app/views/users/*
157. Template Contents <h1>Users</h1> <%= render "my_template" %> I guess this is a png? index.html.erb _my_template.png.erb <cool> XML is cool! </cool> _my_template.xml.erb
158. Requests and Rendering Request Response Template Rendered curl -H 'Accept: application/xml' http://localhost:3000/users Missing XML template Error None curl -H 'Accept: text/html' http://localhost:3000/users Missing HTML partial Error None Browser Missing HTML partial Error None curl http://localhost:3000/users <h1>Users</h1> I guess this is a png? index.html.erb _my_template.png.erb
159. Error!!
160. Requests and Rendering Request Response Template Rendered curl -H 'Accept: application/xml' http://localhost:3000/users Missing XML template Error None curl -H 'Accept: text/html' http://localhost:3000/users Missing HTML partial Error None Browser Missing HTML partial Error None curl http://localhost: 3000/users <h1>Users</h1> I guess this is a png? index.html.erb _my_template.png.erb
161. We Can’t Predict <h1>Users</h1> <%= render "my_template" %>
162. respond_to Controller class UsersController < ApplicationController # GET /users # GET /users.json def index @users = User.all render "index" end end class UsersController < ApplicationController # GET /users # GET /users.json def index @users = User.all respond_to do |format| format.html do render "index" end end end end "Bare" render respond_to render
163. Requests and Rendering Request Response Template Rendered curl -H 'Accept: application/ xml' http://localhost:3000/ users Missing XML template Error None curl -H 'Accept: text/html' http://localhost:3000/users Missing HTML partial Error None Browser Missing HTML partial Error None curl http://localhost:3000/ users Missing HTML partial Error None
164. Context Dependent <h1>Users</h1> <%= render "my_template" %> class UsersController < ApplicationController # GET /users # GET /users.json def index @users = User.all render "index" end end class UsersController < ApplicationController # GET /users # GET /users.json def index @users = User.all respond_to do |format| format.html do render "index" end end end end index.html.erb
165. Templates are not "Context Free"
166. Prediction and Consistency
167. Find a Template (from the cache) Compiled? Compile the Template Call the method Calculate a Method Name Cheap! Cheap! Expensive!
168. What Method Will This Call? <h1>Users</h1> <%= render "my_template" %> <h1>Users</h1> <%= render_my_template_00011123abf %> index.html.erb translated template Calls a unique method. But what method?
169. Find a Template (from the cache) Compiled? Compile the Template Call the method Calculate a Method Name Cheap! Cheap! Expensive!
170. #SPOILER
171. Slower Production Boot (but could be eliminated by BootSnap)
172. Lower Memory
173. Faster Runtime No More "Cache Check" Penalty
174. DETOUR!
175. Three Templates <ul> <%= render partial: "customer", collection: customers %> </ul> <ul> <%= render partial: "customer", collection: customers, cached: true %> </ul> _col.html.erb _cached_col.html.erb <li> Hello: <%= customer.name %> </li> _customer.html.erb
176. Benchmark https://github.com/rails/rails/issues/35257
177. Results $ be ruby render_benchmark.rb -- create_table(:customers, {:force=>true}) -> 0.0108s <#ActiveSupport::Cache::MemoryStore entries=1000, size=333893, options={}> Warming up -------------------------------------- collection render: no cache 6.000 i/100ms collection render: with cache 1.000 i/100ms Calculating ------------------------------------- collection render: no cache 65.319 (± 7.7%) i/s - 330.000 in 5.080651s collection render: with cache 11.504 (± 8.7%) i/s - 58.000 in 5.071030s Comparison: collection render: no cache: 65.3 i/s collection render: with cache: 11.5 i/s - 5.68x slower
178. I was convinced the cache didn’t work
179. I was convinced the cache didn’t work
180. I was convinced the cache didn’t work
181. I was convinced the cache didn’t work
182. But, there were entries in the cache
183. BUT AT WHAT COST?
184. Profiled The Cache ================================== Mode: wall(1000) Samples: 4690 (0.00% miss rate) GC: 207 (4.41%) ================================== TOTAL (pct) SAMPLES (pct) FRAME 594 (12.7%) 594 (12.7%) ActiveModel::LazyAttributeHash#[] 387 (8.3%) 387 (8.3%) ActiveRecord::Transactions#update_attributes_from_transaction_state 1199 (25.6%) 246 (5.2%) ActiveSupport::Cache::Store#expanded_key 301 (6.4%) 218 (4.6%) AbstractController::Caching::Fragments#combined_fragment_cache_key 207 (4.4%) 207 (4.4%) (garbage collection) 932 (19.9%) 196 (4.2%) ActionView::CollectionCaching#collection_by_cache_keys 450 (9.6%) 181 (3.9%) ActiveSupport::Cache::Store#expanded_version
185. Cache Key Calculation Was More Expensive Than Template Execution
186. Cache Payoff <li> Hello: <%= customer.name %> </li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> <li>Hello: <%= customer.name %></li> Old Template New Template
187. Benchmark Results $ be ruby render_benchmark.rb -- create_table(:customers, {:force=>true}) -> 0.0075s <#ActiveSupport::Cache::MemoryStore entries=1000, size=900893, options={}> Warming up -------------------------------------- collection render: no cache 4.000 i/100ms collection render: with cache 4.000 i/100ms Calculating ------------------------------------- collection render: no cache 41.066 (± 2.4%) i/s - 208.000 in 5.070051s collection render: with cache 43.192 (± 4.6%) i/s - 216.000 in 5.012803s Comparison: collection render: with cache: 43.2 i/s collection render: no cache: 41.1 i/s - same-ish: difference falls within error
188. "Cache" doesn’t mean "fast"
189. Speeding Up Templates
190. Template Static Analysis
191. Pre-Compiling Templates https://github.com/jhawthorn/actionview_precompiler/
192. ActionviewPrecompiler.precompile
193. Static Analysis <%= render "no_locals" %> <%= render "static_locals", locals: { foo: bar } %> <%= render "dynamic_locals", locals: { foo: bar }.merge(baz) %> Can Precompile! Can Precompile! Nope!
194. Predicting "Render" Methods
195. "Same Format Assumption" <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :png %> $ tree app/views/users app/views/users !"" _my_template.html.erb !"" _my_template.png.erb !"" _my_template.xml.erb #"" index.html.erb index.html.erb templates
196. Ambiguous Render Problem <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :html %> $ tree app/views/users app/views/users !"" _my_template.png.erb !"" _my_template.xml.erb #"" index.html.erb index.html.erb templates Sometimes an exception Sometimes a PNG Always an exception
197. "Always Optimize" <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :html %> <h1>Users</h1> <%= render "my_template", format: :png %> <%= render "my_template", format: :html %> index.html.erb index.html.erb
198. "Same Format Assumption" <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :png %> $ tree app/views/users app/views/users !"" _my_template.html.erb !"" _my_template.png.erb !"" _my_template.xml.erb #"" index.html.erb index.html.erb templates
199. "Same Format Assumption" <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :png %> <h1>Users</h1> <%= render_my_template_html_00123abc %> <%= render_my_template_png_00123abc %> index.html.erb Optimized Template
200. Ambiguous Render Problem <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :html %> $ tree app/views/users app/views/users !"" _my_template.png.erb !"" _my_template.xml.erb #"" index.html.erb index.html.erb templates
201. Ambiguous Render Problem <h1>Users</h1> <%= render "my_template" %> <%= render "my_template", format: :html %> <h1>Users</h1> <%= render "my_template" %> <%= raise MissingTemplateError %> index.html.erb Optimized Template
202. Wrap It Up
203. Be "Context Free" Don’t depend on side effects
204. Be Consistent
205. Cache != Fast
206. Benchmark First!
207. Keep Building Apps!
208. Thank You!!!