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Fibers

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An
 introduction
 to Denis Defreyne
 Ruby Wine
 April 13th, 2019 Fibers

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3 1.

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3 1. 2.

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Basics 4

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5 f = lambda do puts "giraffe" end f.call

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5 f = lambda do puts "giraffe" end f.call giraffe

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6 f = Fiber.new do puts "giraffe" end f.resume

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6 f = Fiber.new do puts "giraffe" end f.resume giraffe

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Photo by Harshil Gudka on Unsplash

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8 f = lambda do puts "zebra" end f.call zebra

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9 f = lambda do puts "zebra" return puts "invisible zebra" end f.call

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9 f = lambda do puts "zebra" return puts "invisible zebra" end f.call zebra

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10 f = Fiber.new do puts "zebra" return puts "invisible zebra" end f.resume

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10 f = Fiber.new do puts "zebra" return puts "invisible zebra" end f.resume zebra

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10 f = Fiber.new do puts "zebra" return puts "invisible zebra" end f.resume zebra sample.rb:3:
 in `block in ':
 unexpected return
 (LocalJumpError)

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11 f = Fiber.new do puts "zebra" Fiber.yield puts "invisible zebra" end f.resume

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11 f = Fiber.new do puts "zebra" Fiber.yield puts "invisible zebra" end f.resume zebra

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Photo by Arleen wiese on Unsplash

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13 f = lambda do puts "donkey" end f.call
 donkey

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14 f = lambda do puts "donkey" end f.call f.call

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14 f = lambda do puts "donkey" end f.call f.call donkey donkey

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15 f = Fiber.new do puts "donkey" end f.resume f.resume

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15 f = Fiber.new do puts "donkey" end f.resume f.resume donkey

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15 f = Fiber.new do puts "donkey" end f.resume f.resume donkey a.rb:6:
 in `resume':
 dead fiber called
 (FiberError)

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Photo by Spencer Watson on Unsplash

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17 f = lambda do puts "kangaroo" return puts "wallaby" end f.call
 kangaroo


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18 f = lambda do puts "kangaroo" return puts "wallaby" end f.call f.call

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18 f = lambda do puts "kangaroo" return puts "wallaby" end f.call f.call kangaroo kangaroo

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19 f = Fiber.new do puts "kangaroo" Fiber.yield puts "wallaby" end f.resume f.resume

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19 f = Fiber.new do puts "kangaroo" Fiber.yield puts "wallaby" end f.resume f.resume kangaroo wallaby

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Photo by Austin Elder on Unsplash

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Image by sandid from Pixabay

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22 f = Fiber.new { … } Create a fiber

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22 f = Fiber.new { … } Create a fiber f.resume Start or resume a fiber

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22 f = Fiber.new { … } Create a fiber f.resume Start or resume a fiber Fiber.yield Return from a fiber

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23 f = Fiber.new do puts 'quokka' end f.resume quokka

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24 f = Fiber.new do |a| puts a end f.resume('quokka')

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24 f = Fiber.new do |a| puts a end f.resume('quokka') quokka

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Image by Tracey Wong from Pixabay

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26 f = Fiber.new do |a| puts a
 
 end f.resume('samoyed')
 samoyed

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27 f = Fiber.new do |a| puts a Fiber.yield puts 'arctic fox' end f.resume('samoyed') f.resume samoyed
 arctic fox

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28 f = Fiber.new do |a| puts a b = Fiber.yield puts b end f.resume('samoyed') f.resume('arctic fox')

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28 f = Fiber.new do |a| puts a b = Fiber.yield puts b end f.resume('samoyed') f.resume('arctic fox') samoyed arctic fox

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Image by coolcoolleah from Pixabay

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Photo by Jonatan Pie on Unsplash

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31 f = Fiber.new do puts 'red panda' end f.resume red panda

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32 f = Fiber.new do 'red panda' end puts f.resume

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32 f = Fiber.new do 'red panda' end puts f.resume red panda

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Photo by Michael Payne on Unsplash

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34 f = Fiber.new do puts 'maine coon' end f.resume maine coon


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35 f = Fiber.new do puts 'maine coon' Fiber.yield 'raccoon' end f.resume puts f.resume maine coon
 raccoon

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36 f = Fiber.new do
 Fiber.yield('maine coon')
 'raccoon' end puts f.resume puts f.resume

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36 f = Fiber.new do
 Fiber.yield('maine coon')
 'raccoon' end puts f.resume puts f.resume maine coon raccoon

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Photo by Bee Felten-Leidel on Unsplash

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Photo by Gary Bendig on Unsplash

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39 f = Fiber.new { |…| … } Create a fiber

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39 f = Fiber.new { |…| … } Create a fiber r = f.resume(…) Start or resume a fiber

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39 f = Fiber.new { |…| … } Create a fiber r = f.resume(…) Start or resume a fiber a = Fiber.yield(…) Return from a fiber

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Three Practical Applications 40

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1. Generators 41

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42 [7, 2, 4].each do |num| puts num end 7 2 4

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43 class PeopleDirectory end

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44 class PeopleDirectory RADIA = 'Dr. Radia Perlman' KATIE = 'Dr. Katie Bouman' ANITA = 'Dr. Anita Borg' end

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45 class PeopleDirectory RADIA = 'Dr. Radia Perlman' KATIE = 'Dr. Katie Bouman' ANITA = 'Dr. Anita Borg' def each end end

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46 class PeopleDirectory RADIA = 'Dr. Radia Perlman' KATIE = 'Dr. Katie Bouman' ANITA = 'Dr. Anita Borg' def each yield RADIA yield KATIE yield ANITA end end

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47 class PeopleDirectory RADIA = 'Dr. Radia Perlman' KATIE = 'Dr. Katie Bouman' ANITA = 'Dr. Anita Borg' def each yield RADIA yield KATIE yield ANITA end end PeopleDirectory.new

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48 class PeopleDirectory RADIA = 'Dr. Radia Perlman' KATIE = 'Dr. Katie Bouman' ANITA = 'Dr. Anita Borg' def each yield RADIA yield KATIE yield ANITA end end PeopleDirectory.new.each do |name| puts name end

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49 class PeopleDirectory RADIA = 'Dr. Radia Perlman' KATIE = 'Dr. Katie Bouman' ANITA = 'Dr. Anita Borg' def each yield RADIA yield KATIE yield ANITA end end PeopleDirectory.new.each do |name| puts name end Dr. Radia Perlman Dr. Katie Bouman Dr. Anita Borg

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50 class LinearCongruentialGenerator 
 
 


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51 class LinearCongruentialGenerator M = 0x7FFFFFF A = 1103515245 C = 12345

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52 class LinearCongruentialGenerator M = 0x7FFFFFF A = 1103515245 C = 12345 def initialize(seed) @value = seed end

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53 class LinearCongruentialGenerator M = 0x7FFFFFF A = 1103515245 C = 12345 def initialize(seed) @value = seed end def next @value = (A * @value + C) % M end end

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54 class LinearCongruentialGenerator M = 0x7FFFFFF A = 1103515245 C = 12345 def initialize(seed) @value = seed end def next @value = (A * @value + C) % M end end rng = LinearCongruentialGenerator.new(123)

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55 class LinearCongruentialGenerator M = 0x7FFFFFF A = 1103515245 C = 12345 def initialize(seed) @value = seed end def next @value = (A * @value + C) % M end end rng = LinearCongruentialGenerator.new(123) p rng.next p rng.next p rng.next

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56 class LinearCongruentialGenerator M = 0x7FFFFFF A = 1103515245 C = 12345 def initialize(seed) @value = seed end def next @value = (A * @value + C) % M end end rng = LinearCongruentialGenerator.new(123) p rng.next p rng.next p rng.next 440917719 357222964 2107447239

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57 class LinearCongruentialGenerator # … 
 
 def each end end
 
 


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58 class LinearCongruentialGenerator # … 
 
 def each loop do end end end
 
 


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59 class LinearCongruentialGenerator # … 
 
 def each loop do self.next end end end
 
 


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60 class LinearCongruentialGenerator # … 
 
 def each loop do self.next yield(@value) end end end
 
 


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61 class LinearCongruentialGenerator # … include Enumerable def each loop do self.next yield(@value) end end end
 
 


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62 class LinearCongruentialGenerator # … include Enumerable def each loop do self.next yield(@value) end end end
 
 rng = LinearCongruentialGenerator.new(123)


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63 class LinearCongruentialGenerator # … include Enumerable def each loop do self.next yield(@value) end end end
 
 rng = LinearCongruentialGenerator.new(123)
 p rng.take(3)

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64 class LinearCongruentialGenerator # … include Enumerable def each loop do self.next yield(@value) end end end
 
 rng = LinearCongruentialGenerator.new(123)
 p rng.take(3) [440917719, 357222964, 2107447239]

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65 M = 0x7FFFFFFF A = 1103515245 C = 12345 
 
 
 
 


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66 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) end
 
 
 
 


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67 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do end end
 
 
 
 


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68 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do loop do end end end
 
 
 
 


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69 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do loop do value = (A * value + C) % M end end end
 
 
 
 


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70 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do loop do value = (A * value + C) % M Fiber.yield(value) end end end
 
 
 
 


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71 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do loop do value = (A * value + C) % M Fiber.yield(value) end end end
 
 rng = make_rng(123) 
 


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72 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do loop do value = (A * value + C) % M Fiber.yield(value) end end end
 
 rng = make_rng(123) p rng.resume
 p rng.resume
 p rng.resume

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73 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Fiber.new do loop do value = (A * value + C) % M Fiber.yield(value) end end end
 
 rng = make_rng(123) p rng.resume
 p rng.resume
 p rng.resume 440917719 357222964 2107447239

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74 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Enumerator.new do |enum| loop do value = (A * value + C) % M enum.yield(value) end end end
 
 rng = make_rng(123) p rng.next
 p rng.next
 p rng.next 440917719 357222964 2107447239

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75 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Enumerator.new do |enum| loop do value = (A * value + C) % M enum.yield(value) end end end
 
 rng = make_rng(123) p rng.next
 p rng.next
 p rng.next 440917719 357222964 2107447239

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76 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Enumerator.new do |enum| loop do value = (A * value + C) % M enum.yield(value) end end end
 
 rng = make_rng(123) p rng.take(2)
 


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77 M = 0x7FFFFFFF A = 1103515245 C = 12345 def make_rng(value) Enumerator.new do |enum| loop do value = (A * value + C) % M enum.yield(value) end end end
 
 rng = make_rng(123) p rng.take(2)
 
 [440917719, 357222964]

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1. Generators ✓ 78

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2. Resumable computation 79

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80

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81 def compile end

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82 def compile queue = PriorityQueue.new(pages) end

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83 def compile queue = PriorityQueue.new(pages) until queue.empty? end end

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84 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next end end

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85 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next compile_page(page) end end

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87 def compiled_content_of(page) @compiled_content[page] end


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88 def compiled_content_of(page) unless @compiled_content.key?(page) raise MissingDependencyError.new(page) end @compiled_content[page] end

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89 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next
 
 compile_page(page)
 
 
 
 end end

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90 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next begin compile_page(page) rescue MissingDependencyError => error end end end

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91 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next begin compile_page(page) rescue MissingDependencyError => error queue.add(page) end end end

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92 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next begin compile_page(page) rescue MissingDependencyError => error queue.add(page) queue.prioritize(error.missing_page) end end end

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95 def fiber_for(page) @fibers[page] ||= Fiber.new { compile_page(page) } end

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96 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next fiber_for(page).resume end end

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97 def compiled_content_of(page) unless @compiled_content.key?(page) Fiber.yield(MissingDependency.new(page)) end @compiled_content[page] end

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98 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next result = fiber_for(page).resume end end

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99 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next result = fiber_for(page).resume if result.is_a?(MissingDependency) end end end

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100 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next result = fiber_for(page).resume if result.is_a?(MissingDependency) queue.add(page) end end end

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101 def compile queue = PriorityQueue.new(pages) until queue.empty? page = queue.next result = fiber_for(page).resume if result.is_a?(MissingDependency) queue.add(page) queue.prioritize(result.missing_page) end end end

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102 def compiled_content_of(page) unless @compiled_content.key?(page) Fiber.yield(MissingDependency.new(page)) end @compiled_content[page] end

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2. Resumable computation ✓ 103

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3. Non-blocking I/O 104

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106 urls = [ 'https://denis.ws', 'https://denis.ws/cv', 'https://denis.ws/software', 'https://denis.ws/talks', 'https://denis.ws/toolbox', 'https://nanoc.ws', … ]

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107 Version 1 (sequential)

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108 urls.each do |url| end

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109 urls.each do |url| response = Net::HTTP.get_response(URI.parse(url)) end

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110 urls.each do |url| response = Net::HTTP.get_response(URI.parse(url)) if response.code != "200" end end

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111 urls.each do |url| response = Net::HTTP.get_response(URI.parse(url)) if response.code != "200" puts "Bad URL: #{url}" end end

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112 Version 2 (threaded)

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113 urls.each do |url| response = Net::HTTP.get_response(URI.parse(url)) if response.code != 200 puts "Bad URL: #{url}" end end

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114 urls.each do |url| Thread.new do response = Net::HTTP.get_response(URI.parse(url)) if response.code != 200 puts "Bad URL: #{url}" end end end

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115 threads = urls.map do |url| Thread.new do response = Net::HTTP.get_response(URI.parse(url)) if response.code != 200 puts "Bad URL: #{url}" end end end

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116 threads = urls.map do |url| Thread.new do response = Net::HTTP.get_response(URI.parse(url)) if response.code != 200 puts "Bad URL: #{url}" end end end threads.each(&:join)

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117 Version 3 (non-blocking IO)

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This is a low-level implementation. 118 CAUTION I

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Sockets must never block. 119 CAUTION II

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120 make_request_fiber('denis.ws', '/cv/').resume

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121 def make_request_fiber(host, path) end make_request_fiber('denis.ws', '/cv/').resume

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122 def make_request_fiber(host, path) Fiber.new do end end make_request_fiber('denis.ws', '/cv/').resume

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123 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) end end make_request_fiber('denis.ws', '/cv/').resume

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124 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) end end make_request_fiber('denis.ws', '/cv/').resume

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125 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) connect_ssl(socket) end end make_request_fiber('denis.ws', '/cv/').resume

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126 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) connect_ssl(socket) write(socket, build_http_request(host, path)) end end make_request_fiber('denis.ws', '/cv/').resume

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127 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) connect_ssl(socket) write(socket, build_http_request(host, path)) puts read(socket, 1024) end end make_request_fiber('denis.ws', '/cv/').resume

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128 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) connect_ssl(socket) write(socket, build_http_request(host, path)) puts read(socket, 1024) end end make_request_fiber('denis.ws', '/cv/').resume

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129 def connect_tcp(socket) end

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130 def connect_tcp(socket) socket.connect_tcp end

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131 def connect_tcp(socket) case socket.connect_tcp when :wait_readable when :wait_writable else end end

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132 def connect_tcp(socket) case socket.connect_tcp when :wait_readable Fiber.yield when :wait_writable else end end

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133 def connect_tcp(socket) case socket.connect_tcp when :wait_readable Fiber.current Fiber.yield when :wait_writable else end end

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134 def connect_tcp(socket) case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield when :wait_writable else end end

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135 make_request_fiber('denis.ws', '/cv/').resume

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136 make_request_fiber('denis.ws', '/cv/').resume # … fiber got suspended; now what?

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137 IO.select( )

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138 IO.select( $awaiting_readable.keys, $awaiting_writable.keys, )

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139 readable, writable = IO.select( $awaiting_readable.keys, $awaiting_writable.keys, )

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140 readable, writable = IO.select( $awaiting_readable.keys, $awaiting_writable.keys, ) readable.each do |socket| end

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141 readable, writable = IO.select( $awaiting_readable.keys, $awaiting_writable.keys, ) readable.each do |socket| fiber = $awaiting_readable.fetch(socket) end

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142 readable, writable = IO.select( $awaiting_readable.keys, $awaiting_writable.keys, ) readable.each do |socket| fiber = $awaiting_readable.fetch(socket) fiber.resume end

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143 readable, writable = IO.select( $awaiting_readable.keys, $awaiting_writable.keys, ) readable.each do |socket| fiber = $awaiting_readable.fetch(socket) fiber.resume end writable.each do |socket| fiber = $awaiting_writable.fetch(socket) fiber.resume end

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144 loop do readable, writable = IO.select( $awaiting_readable.keys, $awaiting_writable.keys, ) readable.each do |socket| fiber = $awaiting_readable.fetch(socket) fiber.resume end writable.each do |socket| fiber = $awaiting_writable.fetch(socket) fiber.resume end end

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145 def connect_tcp(socket) case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield when :wait_writable else end end

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146 def connect_tcp(socket) case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield $awaiting_readable.delete(socket) when :wait_writable else end end

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147 def connect_tcp(socket) case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield $awaiting_readable.delete(socket) when :wait_writable Fiber.yield else end end

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148 def connect_tcp(socket) case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield $awaiting_readable.delete(socket) when :wait_writable $awaiting_writable[socket] = Fiber.current Fiber.yield else end end

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149 def connect_tcp(socket) case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield $awaiting_readable.delete(socket) when :wait_writable $awaiting_writable[socket] = Fiber.current Fiber.yield $awaiting_writable.delete(socket) else end end

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150 def connect_tcp(socket) loop do case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield $awaiting_readable.delete(socket) when :wait_writable $awaiting_writable[socket] = Fiber.current Fiber.yield $awaiting_writable.delete(socket) else end end end

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151 def connect_tcp(socket) loop do case socket.connect_tcp when :wait_readable $awaiting_readable[socket] = Fiber.current Fiber.yield $awaiting_readable.delete(socket) when :wait_writable $awaiting_writable[socket] = Fiber.current Fiber.yield $awaiting_writable.delete(socket) else break end end end

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152 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) connect_ssl(socket) write(socket, build_http_request(host, path)) puts read(socket, 1024) end end make_request_fiber('denis.ws', '/cv/').resume

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153 def make_request_fiber(host, path) Fiber.new do socket = NonBlockingSSLSocket.new(host, 443) connect_tcp(socket) connect_ssl(socket) write(socket, build_http_request(host, path)) puts read(socket, 1024) end end make_request_fiber('denis.ws', '/cv/').resume

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154 def connect_ssl(socket) end

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155 def connect_ssl(socket) socket.connect_ssl end

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156 def connect_ssl(socket) case socket.connect_ssl end

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157 def connect_ssl(socket) case socket.connect_ssl when :wait_readable when :wait_writable else end end

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157 def connect_ssl(socket) case socket.connect_ssl when :wait_readable when :wait_writable else end end

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158 require 'async' require 'async/http'

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159 require 'async' require 'async/http' endpoint = Async::HTTP::URLEndpoint.parse('https://denis.ws')

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160 require 'async' require 'async/http' endpoint = Async::HTTP::URLEndpoint.parse('https://denis.ws') client = Async::HTTP::Client.new(endpoint)

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161 require 'async' require 'async/http' endpoint = Async::HTTP::URLEndpoint.parse('https://denis.ws') client = Async::HTTP::Client.new(endpoint) Async do |task| end

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162 require 'async' require 'async/http' endpoint = Async::HTTP::URLEndpoint.parse('https://denis.ws') client = Async::HTTP::Client.new(endpoint) Async do |task| task.async { p client.get("/").status } task.async { p client.get("/cv/").status } task.async { p client.get("/software/").status } task.async { p client.get("/talks/").status } task.async { p client.get("/toolbox/").status } end

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162 require 'async' require 'async/http' endpoint = Async::HTTP::URLEndpoint.parse('https://denis.ws') client = Async::HTTP::Client.new(endpoint) Async do |task| task.async { p client.get("/").status } task.async { p client.get("/cv/").status } task.async { p client.get("/software/").status } task.async { p client.get("/talks/").status } task.async { p client.get("/toolbox/").status } end https://github.com/socketry/async

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3. Non-blocking I/O ✓ 163

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164 1.

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164 1. 2.

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164 1. 2. 3.

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165 f = Fiber.new { |…| … } Create a fiber

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165 f = Fiber.new { |…| … } Create a fiber r = f.resume(…) Start or resume a fiber

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165 f = Fiber.new { |…| … } Create a fiber r = f.resume(…) Start or resume a fiber a = Fiber.yield(…) Return from a fiber

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Now you know everything about Fibers.

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Q&A Find me at @ddfreyne on Twitter, or at denis.ws!