Friendly and Modern AsyncIO

AsyncIO is a powerful mechanism for building high-performance services, but it has long been thought of as “too complicated”. But it’s easier than you might think, and with Python 3.7, it’s easier than ever to get started using just the standard library! We'll cover the basics of AsyncIO, take a look at the latest features in 3.7, build friendly and expressive APIs, analyze best practices for third-party libraries, and discuss integrating async code with synchronous libraries and codebases.

Transcript

2. Friendly and Modern AsyncIO John Reese Production Engineer, Python Foundation @n7cmdr
 github.com / jreese
3. 1. What is AsyncIO 2. Why is it useful 3. High level concepts 4. Standard library basics 5. Building friendly, asynchronous APIs Topics
4. github.com/jreese/pycon
5. github.com/jreese/pycon $ git clone https://github.com/jreese/pycon $ cd pycon/friendly-asyncio $ python3.7 -m venv venv $ source venv/bin/activate $ pip install -Ur requirements.txt
6. What is AsyncIO
7. • Cooperative multitasking • Built around futures/promises • Single threaded • Optimized for concurrent I/O What is AsyncIO
8. • Cooperative multitasking • Built around futures/promises • Single threaded • Optimized for concurrent I/O What is AsyncIO
9. • Parallel execution • Multithreaded • Performance/speed improvement • Optimized for computation What AsyncIO is not
10. • Parallel execution • Multithreaded • Performance/speed improvement • Optimized for computation What AsyncIO is not
11. • Context switching • Thread safety • Control flow • “How many?” Why not threads?
12. • Context switching • Thread safety • Control flow • “How many?” Why not threads?
13. $ python3.7 1-threads.py 1299 runs of fib in 1.0s: 769.83 usec per run
15. 156 runs of fibs in 1.0s: 6.42 msec per run 151 runs of fibp in 1.0s: 6.65 msec per run
16. 156 runs of fibs in 1.0s: 6.44 msec per run 387 runs of fibp in 1.0s: 2.59 msec per run
17. But what about I/O?
18. • Simple TCP server • Accepts an upper bound k • “Thinks about it” • Returns a random integer [0,k] Randint-as-a-service $ python3.7 server.py listening on 8080...
19. $ echo 20 | nc ::1 8080 6 $ echo 20 | nc ::1 8080 17 $ echo 20 | nc ::1 8080 11
20. $ python3.7 2-thread-client.py got 19
21. 10 runs of get_random in 1.0s: 0.104 sec per run
22. 1 runs of many_random in 3.4s: 3.419 sec per run
23. 2 runs of many_random in 1.1s: 0.558 sec per run 1 runs of many_random in 1.4s: 1.351 sec per run 1 runs of many_random in 1.2s: 1.241 sec per run 0 0.001 0.002 0.003 0.004 32 64 128 256 512 1024
24. $ python3.7 3-asyncio-client.py 10 runs of get_random in 1.0s: 0.105 sec per run
25. 7 runs of async_random in 1.0s: 0.147 sec per run
26. 6 runs of async_random in 1.1s: 0.191 sec per run 4 runs of async_random in 1.1s: 0.280 sec per run 3 runs of async_random in 1.4s: 0.467 sec per run 0 0.001 0.002 0.003 0.004 32 64 128 256 512 1024 128 256 512 1024 AsyncIO Threads
27. How does AsyncIO work?
28. • Object that is not ready, or done • “done” means success or exception • Add callbacks, or periodically check state • Result yields final value, or raise exception Back to the futures
29. • Object that is not ready, or done • “done” means success or exception • Add callbacks, or periodically check state • Result yields final value, or raise exception Back to the futures
30. • Like futures, without polling or callbacks • Object with __await__ method • Must be “awaited” via await keyword • Yields value when completed Awaitables
31. • Asynchronous function • Dedicated async def syntax • Returns a coroutine object when called • Only executes when awaited Coroutines
32. • Event loop controls execution of pending tasks • Tasks wrap and await futures automatically • Tasks are awaitable, yield their wrapped futures Event loops and tasks
33. • Executes current task until done or blocked • Next task picked from queue • Tasks can “starve” other tasks Event loops and tasks
34. $ python3.7 4-asyncio-basics.py got coroutine: <coroutine object foo at 0x1017b64c8> running foo got 1 from coroutine
35. $ python3.7 4-asyncio-basics.py got coroutine: <coroutine object foo at 0x1017b64c8> running foo got 1 from coroutine
36. coro: <coroutine object sleep at 0x1049e84c8> task: <Task pending coro=<sleep() running at ...> task: <Task finished coro=<sleep() done, …> result=None>
37. coro: <coroutine object sleep at 0x1049e84c8> task: <Task pending coro=<sleep() running at ...> task: <Task finished coro=<sleep() done, …> result=None>
38. coro: <coroutine object sleep at 0x1049e84c8> task: <Task pending coro=<sleep() running at ...> task: <Task finished coro=<sleep() done, …> result=None>
39. gather two: [0, 11] gather ten: [1, 8, 13, 4, 19, 2, 5, 4, 20, 20]
40. gather two: [0, 11] gather ten: [1, 8, 13, 4, 19, 2, 5, 4, 20, 20]
41. $ python3.7 5-starvation.py getting food full now, took 0.1s
42. getting food nap time nap over full now, took 2.0s
43. getting food nap time nap over full now, took 2.0s
44. getting food nap time full now, took 0.1s nap over
47. 0: counting to 100000 0: ... 99999 ... 100000 1: counting to 100000 1: ... 99999 ... 100000 2: counting to 100000 2: ... 99999 ... 100000 3: counting to 100000 3: ... 99999 ... 100000
50. 0: counting to 100000 1: counting to 100000 2: counting to 100000 3: counting to 100000 0: ... 99999 ... 100000 1: ... 99999 ... 100000 2: ... 99999 ... 100000 3: ... 99999 ... 100000
51. Making AsyncIO useful
59. $ curl http://0.0.0.0:8080/randint/25 15 $ curl http://0.0.0.0:8080/randint/2500 2318 $ python 6-aiohttp-server.py ======== Running on http://0.0.0.0:8080 ======== (Press CTRL+C to quit)
60. $ python3.7 7-aiohttp-client.py got (200, 14)
61. $ python3.7 7-aiohttp-client.py got (200, 14)
67. $ python3.7 8-aiosqlite.py sender> Bob recipient> Alice message> I need your help. inserted row id 1
68. row #1 from Bob to Alice: I need your help. row #2 from Janet to Nina: What time is the developer sync? row #3 from Nina to Janet: I think it's after the design review.
69. Designing Friendly APIs
70. • Focus on common use cases • Make interfaces feel natural • Use the most obvious syntax features • Support multiple styles if possible Obvious and natural
71. • Common, asynchronous actions • Initializing async objects • Preparing or fetching resources Awaitables
72. • Implement the __await__ special method Awaitables
74. $ python3.7 9-awaitables.py 7
75. $ python3.7 9-awaitables.py 23 5
76. • For use in async for loops • Each iteration is an async coroutine • Useful for iteration before all data is ready • Iterate large, async datasets without blocking Async Iterables
77. • Similar to normal iterables • Use __aiter__ to create an iterator • Use __anext__ to return the next value • Raise StopAsyncIteration when exhausted Async Iterables
81. 19 15 1 10 20
82. [34, 9, 28]
83. 0 20 19
84. • Ephemeral actions, connections, transactions • Async coroutines at enter and exit • Ensure clean up on exit or exception Async Context Managers
85. • Same pattern as regular context managers • __aenter__ called when entering • __aexit__ called at exit or exception Async Context Managers
87. $ python3.7 10-contexts.py row #4 from Jack to Jill: I'm out of water. row #5 from Jack to Terry: Do you know where my pail is?
89. Mix Paradigms
90. Phew...
91. Read the [3.7] docs
92. Experimentation is key
93. Consider your workload
94. Don't be afraid to benchmark
95. Don't cross the streams
96. Don't cross the streams
97. Don't cross the streams
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99. ai o uvloop ai ess aioredis aiobot am aiofiles aiosqlite aiopg s aiounittest aioslack trio uvloop omysql aiohttp aiomultiprocess aioredis lack trio uvloop aioitertools aiostream aiofiles a ltiprocess aioredis aiobotocore aiodns aiounittest aiosl aiostream aiofiles aiosqlite aiopg aiomysql aiohttp aiomultipro e aiodns aiounittest aioslack trio uvloop aioitertools aiostream aiof iopg aiomysql aiohttp aiomultiprocess aioredis aiobotocore aiodns ack trio uvloop aioitertools aiostream aiofiles aiosqlite aiopg s aioredis aiobotocore aiodns aiounittest aioslack tr s aiosqlite aiopg aiomysql aiohttp aiomultipr slack trio uvloop aioitertools aiostrea iprocess aioredis aiobotocore stream aiofiles aiosqli aiounittest aio http aio a
100. ai o uvloop ai ess aioredis aiobot am aiofiles aiosqlite aiopg s aiounittest aioslack trio uvloop omysql aiohttp aiomultiprocess aioredis lack trio uvloop aioitertools aiostream aiofiles a ltiprocess aioredis aiobotocore aiodns aiounittest aiosl aiostream aiofiles aiosqlite aiopg aiomysql aiohttp aiomultipro e aiodns aiounittest aioslack trio uvloop aioitertools aiostream aiof iopg aiomysql aiohttp aiomultiprocess aioredis aiobotocore aiodns ack trio uvloop aioitertools aiostream aiofiles aiosqlite aiopg s aioredis aiobotocore aiodns aiounittest aioslack tr s aiosqlite aiopg aiomysql aiohttp aiomultipr slack trio uvloop aioitertools aiostrea iprocess aioredis aiobotocore stream aiofiles aiosqli aiounittest aio http aio a
101. ai o uvloop ai ess aioredis aiobot am aiofiles aiosqlite aiopg s aiounittest aioslack trio uvloop omysql aiohttp aiomultiprocess aioredis lack trio uvloop aioitertools aiostream aiofiles a ltiprocess aioredis aiobotocore aiodns aiounittest aiosl aiostream aiofiles aiosqlite aiopg aiomysql aiohttp aiomultipro e aiodns aiounittest aioslack trio uvloop aioitertools aiostream aiof iopg aiomysql aiohttp aiomultiprocess aioredis aiobotocore aiodns ack trio uvloop aioitertools aiostream aiofiles aiosqlite aiopg s aioredis aiobotocore aiodns aiounittest aioslack tr s aiosqlite aiopg aiomysql aiohttp aiomultipr slack trio uvloop aioitertools aiostrea iprocess aioredis aiobotocore stream aiofiles aiosqli aiounittest aio http aio a
102. github.com/jreese/pycon
103. github.com/jreese/pycon John Reese Production Engineer, Python Foundation @n7cmdr
 github.com / jreese