How Does Async Work?

If you work with Node.js or Python you might have heard of asynchronous programming a.k.a. async/await.
It lets you do something else while you wait on some work to be done in the background - like reading a file or sending some data over the network.
But what is it, really? And are there differences between the programming languages?
Let's go on a trip through async-land and discover callbacks, event loops, and state machines.
We will look at Node's, Python's, and Rust's async features and how they work under the hood.

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1. How does

   Async 

   work?
   1
   

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2. ~ Matthias Endler ~
   2
   

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3. ~ Matthias Endler ~
   Backend engineer at trivago
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4. ~ Matthias Endler ~
   Backend engineer at trivago
   Mostly Go, Rust, Python
   2
   

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5. ~ Matthias Endler ~
   Backend engineer at trivago
   Mostly Go, Rust, Python
   Interested in low level stuff
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6. ~ Matthias Endler ~
   Backend engineer at trivago
   Mostly Go, Rust, Python
   Interested in low level stuff
   endler.dev and Hello-rust.show
   2
   

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9. 4
   move
   

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10. 4
    move
    

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11. 4
    move
    

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12. 4
    move
    

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13. ~ Python ~
    5
    

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21. Python's asyncio
    * coroutines
    * tasks
    * event loop
    * select
    11
    

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24. 13
    coroutine
    

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25. 14
    coroutine
    asyncio.gather( )
    

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26. 14
    coroutine
    Task
    

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27. 15
    asyncio.run( )
    

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28. 15
    Task
    

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32. 18
    select
    kernel
    userspace
    

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33. 18
    select
    kernel
    userspace
    

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34. 18
    select
    kernel
    userspace
    

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35. 18
    select
    kernel
    userspace
    

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36. 18
    select
    kernel
    userspace
    

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37. 18
    select
    kernel
    userspace
    

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38. 18
    select
    kernel
    userspace
    

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39. 18
    select
    kernel
    userspace
    

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44. ~ JavaScript ~
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45. Async JavaScript
    * Callbacks
    * Promises
    * async/await
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46. JavaScript Callbacks
    * The problem
    * The solution
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50. 26
    v8
    

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51. 26
    v8 Spidermonkey
    

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52. 26
    v8 Spidermonkey Chakra core
    

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53. 27
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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54. 28
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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55. 28
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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56. 29
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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57. 29
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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58. 30
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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59. 30
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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60. 31
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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61. 31
    Heap Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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62. 32
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    

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63. 33
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    main
    

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64. 34
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    main
    console.log
    

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65. 35
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    main
    

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66. 36
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    main
    SetTimeout
    

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67. 37
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    main cb
    One
    

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68. 37
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    main cb
    One
    

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69. 38
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    main cb
    console.log
    

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70. 39
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    three
    cb
    

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71. 40
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    three
    cb
    

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72. 40
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    three
    cb
    

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73. 41
    Stack
    Web apis
    setTimeout
    dom
    ajax
    callback queue
    Event

    loop
    One
    three
    two
    

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74. 42
    v8 Spidermonkey Chakra core
    

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75. 42
    v8 Spidermonkey Chakra core
    Node.js
    

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77. 44
    Everything You Need to Know About Node.js Event Loop
    

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81. ~ Rust ~
    48
    

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82. What is Rust?
    Empowering everyoneto build

    reliable and efficient software.
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83. What is Rust?
    * Systems programming language
    * Started at Mozilla (firefox)
    * used by Amazon/Microsoft/Dropbox...
    * Main goals: safety, performance
    * fearless concurrency
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85. 52
    Future
    

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89. 56
    start open
    print
    error
    

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90. requests/s
    57
    2.000.000
    1.500.000
    1.000.000
    500.000
    0
    Rust

    (minihttp)
    java

    (rapidoid)
    go

    (fasthttp)
    go

    (stdlib)
    node.js

    (stdlib)
    

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92. Futures in Rust
    59
    mio
    tokio
    futures
    async/await
    select/epoll/kqueue
    Operating system
    external crates
    standard library
    

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93. Summary
    * asyncio in Python is based on coroutines
    * async in javascript is based on
    callbacks
    * Rust's futures are zero-cost
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94. Credits
    * Pixel backgrounds by slance.com
    * Truck and engine logos by Pixelart maker
    * Jake Archibald - in the loop
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