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
2. ~ Matthias Endler ~ 2
3. ~ Matthias Endler ~ Backend engineer at trivago 2
4. ~ Matthias Endler ~ Backend engineer at trivago Mostly Go, Rust, Python 2
5. ~ Matthias Endler ~ Backend engineer at trivago Mostly Go, Rust, Python Interested in low level stuff 2
6. ~ Matthias Endler ~ Backend engineer at trivago Mostly Go, Rust, Python Interested in low level stuff endler.dev and Hello-rust.show 2
9. 4 move
10. 4 move
11. 4 move
12. 4 move
13. ~ Python ~ 5
21. Python's asyncio * coroutines * tasks * event loop * select 11
24. 13 coroutine
25. 14 coroutine asyncio.gather( )
26. 14 coroutine Task
27. 15 asyncio.run( )
28. 15 Task
32. 18 select kernel userspace
33. 18 select kernel userspace
34. 18 select kernel userspace
35. 18 select kernel userspace
36. 18 select kernel userspace
37. 18 select kernel userspace
38. 18 select kernel userspace
39. 18 select kernel userspace
44. ~ JavaScript ~ 22
45. Async JavaScript * Callbacks * Promises * async/await 23
46. JavaScript Callbacks * The problem * The solution 24
50. 26 v8
51. 26 v8 Spidermonkey
52. 26 v8 Spidermonkey Chakra core
53. 27 Heap Stack Web apis setTimeout dom ajax callback queue Event
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54. 28 Heap Stack Web apis setTimeout dom ajax callback queue Event
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55. 28 Heap Stack Web apis setTimeout dom ajax callback queue Event
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56. 29 Heap Stack Web apis setTimeout dom ajax callback queue Event
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57. 29 Heap Stack Web apis setTimeout dom ajax callback queue Event
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58. 30 Heap Stack Web apis setTimeout dom ajax callback queue Event
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59. 30 Heap Stack Web apis setTimeout dom ajax callback queue Event
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60. 31 Heap Stack Web apis setTimeout dom ajax callback queue Event
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61. 31 Heap Stack Web apis setTimeout dom ajax callback queue Event
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62. 32 Stack Web apis setTimeout dom ajax callback queue Event
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63. 33 Stack Web apis setTimeout dom ajax callback queue Event
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64. 34 Stack Web apis setTimeout dom ajax callback queue Event
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65. 35 Stack Web apis setTimeout dom ajax callback queue Event
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66. 36 Stack Web apis setTimeout dom ajax callback queue Event
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67. 37 Stack Web apis setTimeout dom ajax callback queue Event
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68. 37 Stack Web apis setTimeout dom ajax callback queue Event
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69. 38 Stack Web apis setTimeout dom ajax callback queue Event
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70. 39 Stack Web apis setTimeout dom ajax callback queue Event
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71. 40 Stack Web apis setTimeout dom ajax callback queue Event
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72. 40 Stack Web apis setTimeout dom ajax callback queue Event
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73. 41 Stack Web apis setTimeout dom ajax callback queue Event
 loop One three two
74. 42 v8 Spidermonkey Chakra core
75. 42 v8 Spidermonkey Chakra core Node.js
77. 44 Everything You Need to Know About Node.js Event Loop
81. ~ Rust ~ 48
82. What is Rust? Empowering everyoneto build
 reliable and efficient software. 49
83. What is Rust? * Systems programming language * Started at Mozilla (firefox) * used by Amazon/Microsoft/Dropbox... * Main goals: safety, performance * fearless concurrency 50
85. 52 Future
89. 56 start open print error
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)
92. Futures in Rust 59 mio tokio futures async/await select/epoll/kqueue Operating system external crates standard library
93. Summary * asyncio in Python is based on coroutines * async in javascript is based on callbacks * Rust's futures are zero-cost 60
94. Credits * Pixel backgrounds by slance.com * Truck and engine logos by Pixelart maker * Jake Archibald - in the loop 61