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How to write synchronization mechanisms for Fiber

How to write synchronization mechanisms for Fiber

RubyKaigi 2017

seki at druby.org

September 20, 2017
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  1. ͠͹Β͓͘଴͍ͪͩ͘͞
    ✓ ͝ཡͷεϙϯαʔͷఏڙ
    ʹΑΓ͓ૹΓ͠·͢

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  2. slide sponsors
    ְאַせ〢㾊3VCZ⠓陽ח⿫⸇׃׋ְ㖑⯋孖זךד!JXBEPO
    䎢䃊ד׮044(BUF׃׋ְ!LUPV
    E3VCZח״׷ⴓ侔٥8FCفؚٗٓىؚٝ ؔ٦ي爡F#PPL4UPSF
    IUUQ
    FTUPSFPINTIBDPKQUJUMFT1!IJTBTIJN
    !N@TFLJךSF⿾䗁Ꟛ涪׾⿾䗁㷕统׃זָ׵⿾䗁Ꟛ涪חزٓ؎׃גְת
    ׅ!BXB[FLJ
    ⚅歲剑㣐.BTUPEPOչ1BXPPպכ3VCZך⸂ד麊欽׃גתׅ!QJYJW
    〴괏׾⛦׶馉ִ䎢䃊ח⛦׶鴥׿׌涺圫ծ➙䎃׮N@TFLJ眍׾ֶ嚂׃׫ֻ׌ׁ
    ְ剑鵚չ،صًך鋅׵׸倯պהְֲず➂钞׾⠓爡ד⡲׏גתׅךד׉
    ׍׵׮״׹׃ֻדׅկ!UTVCPJ
    ה׍ֺךٖه٦زֶ嚂׃׫חTNBMSVCZֹֹ׋ַ׏׋!WFTUJHF@

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  3. How to write
    synchronization mechanisms
    for Fiber
    [email protected]
    Cookpad, Thank you for paying the travel expenses

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  4. How to write
    synchronization mechanisms
    for Fiber
    [email protected]
    Special thanks to @_sasn for translation

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  5. @m_seki
    衼⡲
    3VCZ؝ىحة
    &3# E3VCZ 3JOEB
    - Ruby committer
    - Author of ERB, dRuby, Rinda

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  6. 2005 - ·ͩॳ࡮Γങ͑·͢
    dRuby
    ʹΑΔ
    ؔকढ़ஶ
    ෼ࢄ
    ɾ
    Web
    ϓϩάϥϛϯά
    First printing from 2005 (Still available)

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  7. 2012 (-2014 ઈ൛)
    Publication from 2012 (Become out of print in 2014)

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  8. 2017 re-published on the web
    Re-published it on the web. CC by SA

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  9. Agenda
    'JCFSךֶׁ׵ְ
    'JCFSⰅꟌ
    &OVNFSBUPS
    4ZODISPOJ[F
    .VMUJQMFYFS
    Agenda
    - Recap: Fiber
    - Introduction of Fiber

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  10. Fiberͷ͓͞Β͍
    1SPDFTT
    5ISFBE
    'JCFS
    Recap: Fiber

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  11. Process ↔ Thread ↔ Fiber
    1SPDFTT
    ًٌٔכⰟ剣׃׋ְ׿׌
    5ISFBE
    ؝ٝذؗأزأ؎حثכ荈ⴓדװ׷
    'JCFS
    - Process
    -- Want to share memories!
    --- Thread
    ---- Do context switch by myself!
    ----- Fiber

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  12. Process
    ⥂隊ׁ׸׋ًٌٔ瑞꟦
    فٔؒٝفذ؍ـז؝ٝذؗأزأ؎حث
    猘חה׏גך䤫׸
    Protected memory space
    preemptive task switch
    my dreams

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  13. Before Process
    فٗإأז׿גזַ׏׋
    ,FZ׾《׶ח遤ֻ
    ⯓遤Ⰵ⸂זח׉׸
    https://www.youtube.com/watch?v=TOnS97C-RGQ

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  14. Before Process (80s)
    04ז׿גזַ׏׋
    1$♧〴ָفٗإأ♧א
    Before Process (80s)
    - There weren't any OS's
    - 1 process, 1 computer

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  15. ϓϩηε΁ͷಌΕ
    ״ֻ׻ַ׵זְֽו铣׿ד׋
    ֿ׿ז⚅歲ָ֮׷ךַ
    A Craving for Processes
    - Didn't get it much, but I used to read it
    - Didn't know such a world

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  16. Before Process (90s)
    ⥂隊ׁ׸זְًٌٔ
    ⼿锃㘗وٕثةأؙ
    ظٝفٔؒٝفذ؍ـ
    ֿ׸'JCFSׄׯ׿
    - no memory protection
    - Cooperative multitasking
    -- non preemptive
    -- Is this a ... Fiber?

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  17. ࣮ࡍͷγεςϜ
    醱侧ךفٗإأה׉׸׵ָⵃ欽ׅ׷项彁
    ر٦ةד圓䧭ׁ׸׷
    ꥫꨄׁ׸׋ًٌٔ瑞꟦׾馄ִ׷䗳銲ָ֮׷
    فٗإأ׌ֽꥫꨄ׃ג׮穠㽷כ
    The Actual System
    - Assembled by multiple process and the resources that are used by them
    - Needs to jump out of the isolated memory space
    - Isolating processes is one thing, but for the others...

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  18. Processes
    فٗإأ׌ֽד㸣穠׃זְ
    㢩鿇הךꟼ׻׶
    ワ鴟鄲縧
    ؿ؋؎ٕ
    ➭ךفٗإأ
    - They don't work alone
    - Works with
    -- devices, storage, other processes

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  19. ProcessͰॻ͘ͱ͖ͷؾ࣋ͪ
    קַךفٗإأהוֲחַ׃גⰟ剣׃״ֲ
    ׭׿וְֻֽׁו
    How you feel when you are using process
    - Try to share with other processes
    -- Even though it's a pain in the neck

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  20. ProcessͰॻ͘ͱ͖ͷؾ࣋ͪ
    Skip!

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  21. IPC͸ΊΜͲ͍͘͞
    QJQF
    4ZTUFN7*1$
    TPDLFU
    ׭׿וֲ׌٦
    IPCs are a pain in the neck too
    - Such a drag

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  22. Thread
    ًٌٔ瑞꟦׾Ⱏ剣ׅ׷⸋⻉晛فٗإأ
    فٔؒٝفذ؍ـז؝ٝذؗأزأ؎حث
    ⸋⻉ה䒷ֹ䳔ִח鯪ꆀ
    㢳ֻך➂חכفٗإأך倯ְְָה䙼ֲ
    degraded version of process that shares memory space
    - The system automatically switches to Thread
    - Bad copy, but lightweight
    To most people, processes are probably better

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  23. ThreadͰॻ͘ͱ͖ͷؾ࣋ͪ
    קַךأٖحسךًٌٔ׾鍗׵זְ״ֲח
    ׮ךׅ׀ֻ孡׾אֽ׷
    孡׾䫙ֻה鍗׏גְ׷
    鍗׏ג׮㣐♱㣗זהֿ׹׌ֽ׾鍗׷

    What it feels like to write Threads

    Try best to be very careful not to change memories of other threads
    - Tend to change it whenever you lose focus
    - Only change the places that are okay to change

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  24. Threadʹඞཁͳၗຫ͞
    չ⥯ֻ׵ְחז׷ה04ח걾׵זֻג׮㸜Ⰻ
    ח⸬桦葺ֻ剅ֽ׷״պ
    ה鎉ִ׷➂ך׋׭ך娀㐻
    04ךؔ٦غ٦قحسָ孡חז׷➂פ
    Attitude when using Threads
    "Secure and efficient coding without OS? No sweat."
    - threads will be a great advantage for you
    - for coders who have concerns about OS overheads

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  25. Fiber
    ظٝفٔؒٝفذ؍ـז⸋⻉晛5ISFBE
    و؎ؙٗأٖحس
    5ISFBEⰻח醱侧ך؝ٝذؗأزָ֮׷
    ⴽךⳢ椚ך鷿⚥פأ؎حثׅ׷
    קה׿וך➂חכ5ISFBEך倯ְְָה䙼ֲ
    A non-preemptive degraded version of Thread
    - Micro thread
    - Has multiple context in one Thread
    - Switches during other jobs
    To most people, Threads are probably better

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  26. Fiberʹඞཁͳࣗ৴
    չ⥯ֻ׵ְחז׷ה3VCZ⚛׫חֲתְأ؛
    آُ٦ָٓ剅ֽ׷״պ
    Attitude when using Fibers
    "Coding a scheduler that's as good as Ruby? Piece of cake."

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  27. FiberͰॻ͘ͱ͖ͷؾ࣋ͪ
    ֲתְ؝ٝذؗأزأ؎حثך⽃⡘׾鋅א
    ֽ״ֲ
    ـٗحׇׁؙזְ״ֲחׅ׷חכ
    ׬׃׹'JCFS׾⢪ֲֿהָ湡涸
    Attitude when using Threads
    "Secure and efficient coding without OS? No sweat."
    - threads will be a great advantage for you
    - for coders who have concerns about OS overheads

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  28. Process ↔ Thread ↔ Fiber
    1SPDFTT
    ًٌٔכⰟ剣׃׋ְ׿׌
    5ISFBE
    ؝ٝذؗأزأ؎حثכ荈ⴓדװ׷
    'JCFS
    - Process
    -- Want to share memory!
    --- Thread
    ---- Do context switch by myself!
    ----- Fiber

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  29. Process ↔ Thread ↔ Fiber
    'JCFS
    荈⹛涸חأ؎حث׃ג״
    5ISFBE
    ًٌٔ⥂隊׃גֻ׸זְה㔭׷׿׌
    1SPDFTT
    ----- Fiber
    ---- Why won't it switch automatically?
    --- Thread
    -- Can't code if it doesn't protect memory!
    - Process

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  30. ͠͹Β͓͘଴͍ͪͩ͘͞
    ✓ ෼͘Β͍͔ͳ
    ✓ 1SPDFTT 5ISFBE 'JCFS
    ✓ ࣍͸'JCFSΛקΊΔΑʂ
    please wait for a moment
    - Done: Process, Thread, and Fiber

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  31. ͳͥFiberͷ࿩Λ͢Δͷ͔
    'JCFS⢪׏׋ؿٖ٦يٙ٦ָؙׅ׀ְ׵׃ְ
    ה耀ְ׋
    ׅ׀ְ׋ְפ׿
    ׅ׀ְְֻ
    Why Fiber?
    Fiber used frameworks are cool
    - from what I heard
    -- is it hard to do?
    -- is it really good?

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  32. ͳͥFiberͷ࿩Λ͢Δͷ͔
    ٙةءع9ד(6*הTPDLFUفؚٗٓىؚٝ
    ָثّحزرٕؗ
    ךדծ荈ⴓד׮剅ְג׫׋ֻז׏׋
    أٖحسד醱侧ךفٗإأה鸐⥋ׅ
    ׷׮ך
    I can socket program with x11 and GUI a little.
    - So, I decided that I'd like to use it myself
    -- Something that communicates with multiple processes with one
    Thread

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  33. ͳͥFiberͷ࿩Λ͢Δͷ͔
    ✮䟝דכ5ISFBE״׶׮ꨇ׃ְה䙼׏׋׿׌
    ֽו׉ך鸐׶ד׃׋ךדծ׫זׁ׿ח׮ֶ
    ׅ׉ⴓֽ׃׋ְ
    I suspected that it would be harder than Threads
    It was. Let me share my experiences with you.

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  34. Fiberೖ໳
    'JCPOBDDJ&OVNFSBUPS
    3EW4J[FE2VFVF DIBOOFM
    .VMUJQMFYFS
    Fiber 101

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  35. ࠷ॳͷςʔϚ
    &OVNFSBUPSך״ֲז圓鸡ךفؚٗٓي׾
    铣׫זָ׵ծ'JCFSך"1*׾㷕ןתׅ
    'JCFSד剅ֹ湫ׅ
    &OVNFSUPSד剅ֹ湫ׅ
    First topic
    We will use an Enumerator like structure to learn Fiber API
    - Rewrite with Fiber
    - Rewrite with Enumerator

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  36. Α͋͘ΔFibonacci
    ٕ٦فד剅ֻה知⽃
    [0, 1]
    [1, 1]
    [2, 2]
    [3, 3]
    [4, 5]
    [5, 8]
    [6, 13]
    [7, 21]
    [8, 34]
    [9, 55]
    Plain Fibonacci
    - Easy to write with Loop
    def fibonacci(n)
    a, b = 1, 1
    n.times do |i|
    p [i, a]
    a, b = b, a + b
    end
    end
    fibonacci(10)

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  37. FiberͰॻ͖௚͢
    ֿ׸׾⢪׏ג"1*׾铡僇׃תׅ
    fib = Fiber.new do
    a, b = 1, 1
    while true
    Fiber.yield(a)
    a, b = b, a + b
    end
    end
    10.times do |n|
    p [n, fib.resume]
    end
    def fibonacci(n)
    a, b = 1, 1
    n.times do |i|
    p [i, a]
    a, b = b, a + b
    end
    end
    fibonacci(10)
    Rewrite with Fiber
    - Explain API using this

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  38. API
    'JCFSOFX
    'JCFSSFTVNF
    'JCFSZJFME

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  39. Fiber.new
    ⴽ'JCFSדװ׶׋ְⳢ椚׾ـٗحؙד床ׅ
    ת׌ـٗحؙך؝٦سח鹌׫תׇ׿
    fib = Fiber.new do
    a, b = 1, 1
    while true
    Fiber.yield(a)
    a, b = b, a + b
    end
    end
    10.times do |n|
    p [n, fib.resume]
    end
    Fiber.new
    - Pass value with another Fiber to do a different job
    - The block code will not run yet.

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  40. Fiber#resume
    'JCFSח؝ٝذؗأز׾ⴖ׶剏ִ׷
    fib = Fiber.new do
    a, b = 1, 1
    while true
    Fiber.yield(a)
    a, b = b, a + b
    end
    end
    10.times do |n|
    p [n, fib.resume]
    end
    Switch context to the Fiber

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  41. Fiber.yield
    SFTVNF׃׋'JCFSחⴖ׶剏ִ׷
    䒷侧ָSFTVNFך⦼חז׷
    fib = Fiber.new do
    a, b = 1, 1
    while true
    Fiber.yield(a)
    a, b = b, a + b
    end
    end
    10.times do |n|
    p [n, fib.resume]
    end
    Switch to fiber.resume
    The argument becomes the value of the fiber

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  42. resume, again
    ✳䏝湡⟃꣬ךSFTVNFכZJFMEַ׵ⱄꟚׅ׷
    fib = Fiber.new do
    a, b = 1, 1
    while true
    Fiber.yield(a)
    a, b = b, a + b
    end
    end
    10.times do |n|
    p [n, fib.resume]
    end
    resume, again
    From the second time on, resume restarts from yield

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  43. resumeͷߦ͖ઌ
    'JCFS׾OFX׃׋׌ֽדכ㹋遤ׁ׸זְ
    SFTVNFד'JCFSח؝ٝذؗأز׾獳ׅ
    ♧䏝湡כ⯓걧פ
    ✳䏝湡⟃꣬כ'JCFSZJFME׃׋הֿ׹פ
    ֿ׸כ⡦䏝湡ךSFTVNFַז
    Where resume jumps to
    Would not execute just by Fiber new
    Pass the value to Fiber by resume
    -- Back to the top on the first round
    -- Back to Fiber.yield from the second round on
    --- Which round am I on...?

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  44. APIΛઆ໌ͨ͠
    SFTVNFהZJFMEך嚊䙀ָה׏אֹחְֻ
    荈歋ֺׅגוֲ׃גְְַ׻ַ׵זְ
    Explained the API
    -The concept of resume and yield is hard to grep
    -Don't know what to do, there are so many things we can do with it

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  45. EnumeratorͰॻ͖௚͢
    ׉׏ֻ׶
    fib = Fiber.new do
    a, b = 1, 1
    while true
    Fiber.yield(a)
    a, b = b, a + b
    end
    end
    10.times do |n|
    p [n, fib.resume]
    end
    def fibonacci
    a, b = 1, 1
    while true
    yield(a)
    a, b = b, a + b
    end
    end
    fib = to_enum(:fibonacci)
    10.times do |n|
    p [n, fib.next]
    end
    Rewrite with Enumerator
    - Nearly identical

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  46. Enumerator
    単׾⡲׷ֿהד罋ִװֻׅז׷
    ֶׅׅ׭
    ❌ 'JCFSךꨇ׃ׁח䩧׍⯘אהְֲ䩛䘔ִ
    ָזְ
    Enumerator
    - Easier to understand when put in a frame
    - Recommended
    ❌ Can't really get the feel of overcoming the difficulties of Fiber

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  47. ͠͹Β͓͘଴͍ͪͩ͘͞
    ✓ &OVNFSBUPSͰ"1*Λઆ໌
    ✓ ೉ָ͕͠͞͠Ίͳ͍
    ✓ ࣍͸3EW
    please wait for a moment
    - Done: Explained the API

    - Next: Synchronizaition

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  48. ࣍ͷςʔϚ
    ず劍䖉׍さ׻ׇ
    Next topic
    - Synchronization

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  49. QueueΛհͨ͠ڠௐ
    2VFVF׾➜׃ג醱侧ך5ISFBEָ鸬䵿ׅ׷
    ׉׸׊׸ך5ISFBEכֶ✼ְ׾濼׵זְ
    欰欵罏ծ嶊顤罏כ醱侧ְג׮⹛ֻ
    q = SizedQueue.new(1)
    Thread.new do
    10.times do |n|
    sleep(rand)
    q.push(n)
    p [:push, n]
    end
    end
    Thread.new do
    10.times do |n|
    sleep(rand)
    p [:pop, q.pop]
    end
    end.join
    Sync with Queue
    - Multiple Threads synchronize through Queue
    - Each Thread does not know anything about other Threads
    - Works with multiple producers and consumers

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  50. ͜ΕͷFiber൛
    3EW׾➜׃ג醱侧ך'JCFSָ鸬䵿ׅ׷
    SFOEF[WPVT
    䖉׍さ׻ׇ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    Fiber version
    - Multiple Fibers work together through Rdv
    - rendez-vous

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  51. rendez-vous


    rendez-vous

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  52. ड͚औΔଆ͕଴ͭ৔߹


    rendez-vous
    When the consumer waits for the producer
    rendezvous

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  53. ͜͏͍͏৔߹΋͋Δ





    rendez-vous
    This might happen

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  54. Rdvͷ࣮૷
    JOJUJBMJ[F
    QVTI
    QPQ
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    Implementation of Rdv

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  55. ࠷ۙ޷͖ͳΠσΟΦϜ
    וֲװ׵ֿ׸׌ֽדֲתֻ剅ֽ׉ֲ
    ה׶ִ֮׆SFTVNF
    遤ֹ鑥ת׏׋׵ZJFME
    My recent favorite idiom
    Feeling that it will go smoothly with these
    - just use resume
    - yield when you're stuck

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  56. ͱΓ͋͑ͣresume
    'JCFSOFX׃׋׵ּׅSFTVNFׅ׷
    5ISFBEOFXך״ֲחּׅ⹛ֹ⳿ׅ
    剑ⴱךSFTVNFך暴ⴽז⹛ֹ׾罋ִזֻ
    ג״ְ
    Just use resume for now
    - Resume right after Fiber.new
    -- Works right away, just like Thread.new
    --- Don't have to think about the special behavior on the first round

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  57. ߦ͖٧·ͬͨΒyield
    װ׸׷ֿהָ֮׷꟦כדֹ׷׌ֽװ׷
    װ׸׷ֿהָזֻז׏׋׵ZJFME
    䖉א湱䩛ח㼎׃גծ荈ⴓ 'JCFSDVSSFOU

    ׾鋙ִג׮׵ֲ
    Yield when you're stuck
    - Do as much as it can while it can do it
    - Yield when it has nothing to do
    -- Let the partner know about yourself (alias fiber.current)

    View full-size slide

  58. initialize
    !SFBEFSכQPQ䖉׍ծ!XSJUFSכQVTI䖉׍
    ך'JCFS׾ًٌׅ׷
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    @reader holds fibers waiting for pop
    @writer holds fibers waiting for push

    View full-size slide

  59. push
    !SFBEFSְָזְהֹծ荈ⴓ׾ًٌ׃ג䖉
    א ZJFME

    !SFBEFSְָ׷הֹծ饯ֿׅ SFTVNF

    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    - When there is no @reader, it records itself and wait (yield)
    - Resume when @reader is present (resume)

    View full-size slide

  60. @reader͕͍ͳ͍
    ر٦ةה'JCFSDVSSFOU׾ًٌ׃גZJFME
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    When @reader is not there
    - Records the data and Fiber.current, then yield

    View full-size slide

  61. @reader͕͍Δ
    !SFBEFS׾♧אSFTVNFׅ׷
    QPQד䖉׏גְ׋'JCFSָⱄꟚׅ׷
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    @reader is present
    - Resume one @reader
    -- Fiber that was waiting for the pop resumes

    View full-size slide

  62. pop
    !XSJUFSְָזְהֹծ荈ⴓ׾ًٌ׃ג䖉
    א ZJFME

    !XSJUFSְָ׷הֹծ饯ֿׅ SFTVNF

    ׉׃גر٦ة׾鵤ׅ
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    When there is no @writer, it records itself and waits (yield)
    - When @writer is present, it resumes (resume)
    -- and returns data
    Skip!

    View full-size slide

  63. @writer͕͍ͳ͍
    'JCFSDVSSFOU׾ًٌ׃גZJFME
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    @writer is gone
    Record Fiber.current and yield
    Skip!

    View full-size slide

  64. @writer͕͍Δ
    !XSJUFS׾♧אSFTVNFׅ׷
    QVTIד䖉׏גְ׋'JCFSָⱄꟚׅ׷
    ַًٌ׵ر٦ة׾鵤ׅ
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    @writer is present
    - Resume one @writer
    -- a Fiber that was waiting for push resumes
    - Returns data value from the note
    Skip!

    View full-size slide

  65. ݕࠪதͷഉଞ੍ޚ
    'JCFSדכ勴⟝嗚叨ך䱖➭ⵖ䖴ָ♶銲
    5ISFBEדכ⽬ꤹ
    def initialize
    @reader = []
    @writer = []
    end
    def push(it)
    if @reader.empty?
    @writer << [it, Fiber.current]
    return Fiber.yield
    end
    @reader.shift.resume(it)
    end
    def pop
    if @writer.empty?
    @reader << Fiber.current
    return Fiber.yield
    end
    value, fiber = @writer.shift
    fiber.resume
    return value
    end
    Exclusive control while inspecting
    - With Fiber, there is no need for exclusive control
    - Very risky on Threads!!

    View full-size slide

  66. Threadͱͷҧ͍
    5ISFBEדכ嗚叨׃גְ׷꟦ח׮؝ٝذؗأ
    زأ؎حثׅ׷
    .POJUPSהַ䗳銲
    䙳ֻגسؗسׅؗ׷
    Difference from Threads
    - Thread context switches during the inspection
    -- needs monitoring
    -- nerve-racking

    View full-size slide

  67. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    How it works.
    Fiber.new
    kara-matz is summoned!
    Fiber.newした

    kara-matzを召喚

    View full-size slide

  68. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    kara-matz is resumed
    It's kara-matz's turn!
    kara-matzをresume

    kara-matzのターン


    View full-size slide

  69. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    kara-matz does push()
    There are no opponents..
    Record data and himself, then yield.
    kara-matzのpush!

    相手がいない。

    自分とデータをメモしyield。ターン終了

    View full-size slide

  70. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    Main's turn!
    Fiber.new
    ichi-matz is summoned!
    メインのターン

    Fiber.new

    ichi-matzを召喚

    View full-size slide

  71. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    ichi-matz resumed
    It's ichi-matz's turn!
    ichi-matzをresume

    ichi-matzのターン


    View full-size slide

  72. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    ichi-matz does pop!
    ichi-matz reads the memo
    takes data. kara-matz resumes the finished.
    ichi-matzのpop!

    ichi-matzはメモを読んだ

    データを手にいれた。kara-matzをresumeしターン終了

    View full-size slide

  73. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    kara-matz does push()
    There are no opponents.
    Record data and himself, then yield.
    kara-matzのpush!

    相手がいない。

    自分とデータをメモしyield。ターン終了

    View full-size slide

  74. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    ichi-matzのpop!

    ichi-matzはメモを読んだ

    データを手にいれた。kara-matzをresumeしターン終了
    ichi-matz does pop!
    ichi-matz reads the memo
    takes data. kara-matz resumes the finished.
    Skip!

    View full-size slide

  75. 㔐װ׶תׅ
    Repeat this 10 times
    Skip!

    View full-size slide

  76. ͏༷͘͝ࢠ
    rdv = Rdv.new
    Fiber.new do
    10.times do |n|
    rdv.push(n)
    p [:push, n]
    end
    end.resume
    Fiber.new do
    10.times do |n|
    p [:pop, rdv.pop]
    end
    end.resume
    ichi-matz dies.
    It's main's turn
    Main dies.
    ichi-matzはしんでしまった

    メインのターン

    メインはしんでしまった
    Skip!

    View full-size slide

  77. ͏͖ͦ͝͏ʂ
    ֲ׀ֹתׅ
    It might work!
    - and it does

    View full-size slide

  78. ͜͜ͷ·ͱΊ
    'JCFSָず劍ׅ׷׋׭ך➬穈׫׾⡲׏׋
    猘ך㥨ֹז؎ر؍ؔي׾荈䢧׃׋
    ה׶ִ֮׆SFTVNF
    遤ֹ鑥ת׏׋׵ZJFME
    Wrapping up
    Made a structure of synchronizing fibers
    Proudly presented my favorite idiom
    - just use resume
    - yield when you're stuck

    View full-size slide

  79. ͜͜ͷ·ͱΊ
    ず劍ך勴⟝嗚叨ח䱖➭ⵖ䖴ְ׵זְ
    农럀涸ח5ISFBEח㢌䳔ׁ׸׷ה㔭׷
    5ISFBE׾⢪׏גְ׋א׮׶ָ㹋כ'JCFS
    ׌׏׋ך倯ְְָה䙼ֲ
    Wrapping up
    We don't need exclusive control when sync-ing
    - Don't want it to be implicitly converted into Threads
    -- It's better off that it was actually Fiber when you thought you were
    using Threads

    View full-size slide

  80. ͠͹Β͓͘଴͍ͪͩ͘͞
    ✓ 'JCFSͷಉظͷ࣮૷
    ✓ 3EW
    ✓ ࣍͸ιέοτϓϩάϥϛ
    ϯά
    please wait for a moment
    - Done: Synchronization 

    - Next: Sockets

    View full-size slide

  81. ࣍ͷςʔϚ
    TPDLFUך؟٦غ٦فؚٗٓىؚٝ
    فٗز؝ٕךⳢ椚׾荈搫ח剅ֹ׋ְ׃ծ醱
    侧ך䱸竲׮䪔ְ׋ְ׿׌ֽו٦
    Next Topic
    - Socket server programming
    - Want to code protocol processes smartly and support multiple
    connections..

    View full-size slide

  82. ͢͢Ί͔ͨ
    E3VCZ؟٦غ٦ך毟⡂؝٦سד铡僇
    稆劰׌ֽו⚛遤ח⹛ַזְ׮ך
    5ISFBE׾欽ְג⚛遤ח⹛ֻ׮ך
    5ISFBE晛׾'JCFS晛ח׃׋׮ך؎و؎
    ث
    ׉ך何葺晛
    Table of Contents:
    explain with dRuby server pseudo code
    - Coding is simple, but doesn't move in parallel
    - Works in parallel with Threads
    - Code above rewritten to use Fiber (bit awkward)
    -- Better version using Fiber

    View full-size slide

  83. ૉ๿͚ͩͲҰ్
    ⽃秪ח♧湫简ח剅ְ׋׮ך
    *0כـٗحؙׅ׷ֽו孡ח׃זְ
    ؙٓ؎،ٝز׃ַ⹛ַזְ
    def main_loop
    loop do
    select
    fds.each do |fd|
    call_callback
    end
    end
    end
    def on_accept
    c = accept
    loop do
    read_request(c)
    do_it
    write_response(c)
    end
    end
    Simple but not parallel
    - Written straight forward
    - Ignore I/O blocks
    - Only works with one client
    def read_n(fd, sz)
    ...
    ...
    end

    View full-size slide

  84. Thread൛
    GE׀הח5ISFBE׾饯⹛ׅ׷
    ֿ׸׌ֽד⚛遤ח⹛ֻ
    def main_loop
    loop do
    select
    fds.each do |fd|
    call_callback
    end
    end
    end
    def on_accept
    c = accept
    Thread.new(c) do |fd|
    loop do
    read_request(fd)
    do_it
    write_response(fd)
    end
    end
    end
    Thread ver
    - Start a new thread on every fd
    - Add 2 columns and it works in parallel
    def read_n(fd, sz)
    ...
    ...
    end
    ௥Ճ͸͚ͩ͜͜
    ௥Ճ͸͚ͩ͜͜

    View full-size slide

  85. Fiber൛
    ظٝفٔؒٝفذ؍ـ
    ׉ךתתדכ⚛遤ח⹛ַזְ
    def main_loop
    loop do
    select
    fds.each do |fd|
    call_callback
    end
    end
    end
    def on_accept
    c = accept
    Fiber.new do
    loop do
    read_request(c)
    do_it
    write_response(c)
    end
    end.resume
    end
    Fiber ver
    - non-preemptive
    - Not quite parallel, yet
    def read_n(fd, sz)
    ...
    ...
    end
    Swapped
    with Fiber

    View full-size slide

  86. Fiber൛վ
    *0ָـٗحؙ׃׉ֲזהֹծֿ׏׉׶؝ٝ
    ذؗأز׾ⴖ׶剏ִ׷⡲䨌
    ـٗحؙ괏ظٝـٗحؙ*0
    def main_loop
    loop do
    select
    fds.each do |fd|
    call_callback
    end
    end
    end
    def on_accept
    c = accept
    Fiber.new do
    loop do
    read_request(c)
    do_it
    write_response(c)
    end
    end.resume
    end
    Fiber ver Revisioned
    - Switch context before it I/O blocks
    -- Blocking-style non-blocking I/O
    def read_n(fd, sz)
    ...
    fd.read_nonblock(sz)
    rescue WaitReadable
    Fiber.yield
    retry
    end

    View full-size slide

  87. Block-ish non-block I/O
    ـٗحؙ׃׉ֲזהֹծ'JCFSZJFME׃ג
    NBJO@MPPQח׮ו׷
    ؝٦ٕغحؙדSFTVNFׅ׷
    def main_loop
    loop do
    select
    fds.each do |fd|
    call_callback
    end
    end
    end
    def on_accept
    c = accept
    Fiber.new do
    loop do
    read_request(c)
    do_it
    write_response(c)
    end
    end.resume
    end
    It Fiber.yields back to main_loop before it I/O blocks
    Resumes on call back
    def read_n(fd, sz)
    ...
    fd.read_nonblock(sz)
    rescue WaitReadable
    Fiber.yield
    retry
    end

    View full-size slide

  88. ίʔϧόοΫͰresume
    ֿך׋׭ח㼭ׁזٓ؎ـٓٔ׾剅ֹת׃׋
    Resumes on call back
    - I made a library to do this

    View full-size slide

  89. Bartender
    GEךSFBEBCMF XSJUBCMFח㼎䘔׃׋؝٦ٕ
    غحָؙ剅ֽ׷׌ֽך噰㼭ךٓ؎ـٓٔ
    https://github.com/seki/bartender
    A tiny callback library that corresponds to fd readable & writable

    View full-size slide

  90. Bartender::Context
    SFBEBCMF XSJUBCMFחז׏׋ֿהח孡בְ׋
    ׵؝٦ٕغحؙ
    ֿ׸׾⢪׏גCMPDLJTIOPOCMPDL*0׾
    Context#[]=(event, fd, callback)
    Πϕϯτछʢ:read, :writeʣͱfdͷ૊ʹίʔϧόοΫΛొ࿥
    Bartender::Context
    Callbacks when readable or writeable
    Use this to implement block-ish non-block I/O
    register callbacks for the combination of event types (:read, :write) and
    fd

    View full-size slide

  91. _read()
    SFBE@OPOCMPDLׅ׷կ⢽㢩ך㜥さכ
    SFBEBCMFחז׷ך׾䖉׏גַ׵SFUSZׅ׷
    䖉׏ג
    ׉ֿד䖉׏׍ׯتً
    ⴽך'JCFSח؝ٝذؗأزأ؎حثׅ׷
    def _read(fd, sz)
    return fd.read_nonblock(sz)
    rescue IO::WaitReadable
    wait_readable(fd)
    retry
    end
    def wait_readable(fd); wait_io(:read, fd); end
    def wait_io(event, fd)
    self[event, fd] = Fiber.current.method(:resume)
    Fiber.yield
    ensure
    delete(event, fd)
    end
    - read_nonblock. On exception, it waits to be readable before it retries.
    - Waits to be what?
    -- We need to context switch to another fiber

    View full-size slide

  92. read_nonblock
    ּׅ铣׭׷ر٦ةָ֮׸ל铣׿ד鵤ׅ
    T[劢弫ך؛٦أ׮״ֻ֮׷
    ּׅח铣׭׷ر٦ةָזְ㜥さחכ⢽㢩
    *08BJU3FBEBCMF
    def _read(fd, sz)
    return fd.read_nonblock(sz)
    rescue IO::WaitReadable
    wait_readable(fd)
    retry
    end
    def wait_readable(fd); wait_io(:read, fd); end
    def wait_io(event, fd)
    self[event, fd] = Fiber.current.method(:resume)
    Fiber.yield
    ensure
    delete(event, fd)
    end
    If there are any readable data, it reads and returns
    - There are cases when it's below sz
    Excepts when there is no readable data
    - IO::WaitReadable

    View full-size slide

  93. wait_io()
    ؝٦ٕغحؙה׃גSFTVNF׾涫ꐮ
    ׉׃ג'JCFSZJFME
    剑穄涸חً؎ٕٝ٦فח䨱׶TFMFDUׅ׷
    SFTVNFׁ׸׋הֹSFBEBCMFחז׏ג׷
    def _read(fd, sz)
    return fd.read_nonblock(sz)
    rescue IO::WaitReadable
    wait_readable(fd)
    retry
    end
    def wait_readable(fd); wait_io(:read, fd); end
    def wait_io(event, fd)
    self[event, fd] = Fiber.current.method(:resume)
    Fiber.yield
    ensure
    delete(event, fd)
    end
    Register resume as callback
    Fiber.yield
    - Goes back to mainloop and selects at the end
    readable when resumed

    View full-size slide

  94. 㹋ꥷך،فٔ؛٦ءّٝד铡僇׃תׅ
    I'll show this to you on an actual application

    View full-size slide

  95. tiny_drbͷൈਮ
    ًحإ٦آ铣׿ד穈׫甧ג׷鿇ⴓדׅ
    ـٗحؙ׾孡חׇ׆⽃秪זSFBE׾⚛ץג׷
    ـٗحؙׅ׷㜥さחכ农럀涸ח؝ٝذؗأ
    ز׾أ؎حث׃תׅ
    def req_drb(reader)
    ref = load(reader, false)
    msg = load(reader)
    argc = load(reader)
    argv = argc.times.collect {load(reader)}
    block = load(reader, false)
    [ref, msg, argv]
    end
    def load(reader, marshal=true)
    sz = reader.read(4)
    sz = sz.unpack('N')[0]
    data = reader.read(sz)
    return data unless marshal
    begin
    Marshal.load(data)
    rescue
    DRb::DRbUnknown.new($!, data)
    end
    end
    extracted from tiny_drb
    - Where it constructs with the read messages
    - Just lining up reads, blocks are ignored
    - When blocked, it context switches implicitly.

    View full-size slide

  96. צҧ͍
    ❌ SFBEBCMFז׵ًحإ٦آ׾ּׅחⰋ鿇铣׭׷
    ❌ XSJUBCMFז׵ًحإ٦آ׾ּׅחⰋ鿇剅ֽ׷
    misinterpretation
    Can read all messages when it's readable
    Can write all messages when its writeable

    View full-size slide

  97. ੲΑ͘ݟͨόά
    TFMFDU
    ך֮הծًحإ٦آ׾铣׿ד穈׫甧
    ג׷ꟼ侧׾؝٦ٕ
    鹼䒀ծꥺ㹱ָ֮׷הةأؙأ؎حثדֹ
    ׆ח㔿ת׷
    Bugs in the good Ol' days (in C)
    - Call functions that read & construct messages after select()
    -- Cannot switch tasks when there is latency and/or incident, and
    freezes

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  98. σϞʢ͸͋Γ·ͤΜʣ
    醱侧ךؙٓ؎،ٝزָ⹛ֻ圫㶨ָTBNQMFח
    剅ְג֮׶תָׅ
    ⹛ַ׃ג׮鋅ג׻ַ׵זַ׏׋ךד
    (There is no) DEMO
    - You can see how multiple clients work in the sample..
    -- But you couldn't really *see* it moving

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  99. tiny_drb.rb
    irb -r drb irb -r drb
    tiny_drb.rb
    Rdv
    https://github.com/seki/bartender/tree/master/sample
    Skip!

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  100. tiny_drbͷ͓΋͠Ζ͍ͱ͜Ζ
    CMPDLJTIOPOCMPDL*0
    僇爙涸זأ؛آُ٦ָٓזְ
    ♧אך'JCFSָ醱侧ך➬穈׫TFMFDU겲ה
    3EWהַהֲתֻ⹛ְגְ׷
    Interesting stuff about tiny_drb
    - block-ish nonblock I/O
    - No written scheduler
    -- One Fiber is working around well with multiple nodes (select, Rdv,
    etc.)

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  101. ଞʹࢼ࡞ͨ͠΋ͷ
    'JCFS晛3JOEB5VQMF4QBDF
    'JCFS晛8SJDL
    '%׾ⵃ欽׃׋5ISFBEהך䖉׍さ׻ׇ
    Other prototypes
    - Rinda::TupleSpace - Fiber edition
    - WEBrick - Fiber edition
    - Synchronize Threads with FD
    Skip!

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  102. Threadͱͷ଴ͪ߹Θͤ
    5ISFBEWBMVFׅ׷ה姺ת׏ג׃תֲ
    *0QJQFךDMPTF׾⢪׏ג穄✪׾鸐濼ׅ׷
    class ThreadTask
    def initialize(*args, &block)
    left, @right = IO.pipe
    @task = Thread.new do
    begin
    block.call(*args)
    ensure
    left.close
    end
    end
    end
    def value
    if @right
    Bartender.wait_readable(@right)
    @right.close
    end
    @task.value
    ensure
    @right = nil
    end
    end
    Sync Threads with FD
    - Stops on Thread.value
    - Notifies stop with IO.pipe close
    Skip!

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  103. Multiplexerͷ·ͱΊ
    ⽃秪ח♧湫简ח剅ֹ׋ְWT⚛遤Ⳣ椚
    5ISFBE⤑ⵃ
    'JCFSד⚛遤䏝♳־׷ךꨇ׃ְ
    CMPDLJTIOPOCMPDL*0׾⡲׏׋
    Multiplexer Wrap-up
    - Simple coding vs parallelism
    - Threads are useful
    - Hard to implement perfect parallel with Fiber
    -- made block-ish non-block I/O

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  104. Fiberೖ໳ͷ·ͱΊ
    'JCPOBDDJ&OVNFSBUPS
    3EW4J[FE2VFVF DIBOOFM
    .VMUJQMFYFS
    ꨇ׃ְ״י
    Fiber 101 Wrap-up
    - Difficult, ain't it?

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  105. ͠͹Β͓͘଴͍ͪͩ͘͞
    ✓ ࣌ؒ͋Δ͔ͳʁ
    ✓ ͓·͚
    please wait for a moment

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  106. ͓·͚
    'JCFSכꨇ׃ְהֿ׹ָ꬗涯ְ
    ➙㔐כֲתְֻ׏׋ֽו㣟侁׃׋鑧
    Digression
    - Fiber is hard, and fun
    - It went well this time, but a story about it *not* working
    Skip?

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  107. ࠓճͷྫ͸
    农鎸דֹ׷ֻ׵ְ㼭ְׁ➬穈׫׌׏׋
    ➬穈׫חさ׻ׇג،فٔ؛٦ءّٝ׾剅
    ֽ׷
    如ך״ֲז縐׾鼘ֽ׵׸׋
    This example
    - Was pretty small, small enough to memorize it all
    -- Can code & adapt according to a particular application
    - Didn't get stuck in the following traps:

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  108. 'JCFSך⚥ד鹼ְⳢ椚׾׃גـٗحؙ
    ㄎ׿׌⯓ד5ISFBE⡲׏גְג'JCFS&SSPS
    ׌׸ַךHFNךזַדְֲֲֿֿהװ׏ג
    ׷ַ׮
    Traps:
    - Get blocked inside Fiber by processing something slow in it
    - Read some place that used a thread and FiberError
    - Somebody might have already done this in gem somewhere

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  109. ͭ·Γ
    ،فٔ؛٦ءّٝך⢪ֲٓ؎ـٓٔךׅ׫
    ׆׫תד㹋鄲׾椚鍑׃גזְהعو׷
    عو׷׏ג鋙ִגֶֽל㣐♱㣗
    㹋כ'JCFSׄׯזֻג׮عو׷
    The point is
    - that you need to understand everything about the library or you'll get
    stuck
    -- If you know that you'll get stuck, you're okay
    --- (Actually, it doesn't need to be Fiber to get stuck)

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  110. ϋϚΔྫ
    'JCFS晛ך5XJUUFSךة؎يٓ؎ٝך铣׫鴥׫
    ⡲׹ֲ
    +40/QBSTFכأزٔ٦ي׾Ⰻ鿇铣׿ד
    4USJOHח׃׍ׯֲ̔تً
    أزٔ٦يַ׵铣׬+40/QBSTFזְ
    Examples of getting stuck
    - Making a Fiber version of Twitter timeline reading
    -- JSON.parse reads and puts everything into a string →Won't work
    - Is there JSON.parse that reads from streams?

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  111. ϋϚΓͦ͏ͳྫ
    3%#.4ךسٓ؎غהַ
    㔿ת׵זְך
    More examples of places to get stuck
    - RDBMS drivers...?
    -- Do they freeze?

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  112. ͠͹Β͓͘଴͍ͪͩ͘͞
    ✓ ͓ΘΓ
    please wait for a moment
    - Almost the end

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  113. ·ͱΊ
    5ISFBEכꨇ׃ְָ'JCFSכ׮׏הꨇ׃ְ
    'JCFSך"1*הず劍ծ*0ך䘔欽⢽׾爙׃׋
    剑鵚㥨ֹז؎ر؍ؔي׾稱➜׃׋
    Summary
    - Threads are hard, but Fibers are even harder
    - Explained Fiber API, synchronization, I/O Multiplexer application
    - Introduced my favorite idiom

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  114. Process ↔ Thread ↔ Fiber
    'JCFS
    荈⹛涸חأ؎حث׃ג״
    5ISFBE
    ًٌٔ⥂隊׃גֻ׸זְה㔭׷׿׌
    1SPDFTT
    ----- Fiber
    ---- Why won't it switch automatically?
    --- Thread
    -- Can't code if it doesn't protect memory!
    - Process

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