Python Asynchronous I/Oasynchronous landscape refresher

Photo by Jake Brown used under CC BY 2.0/“Mono+Balance”

19 Dec 2013 @lukmdo

Agenda 10 minutes

!

• Background (can skip)

• Problem statement

• “Current state”

• Python 3 async horizon (by examples)

⏰

Warmup !

• CPU IO (CPU bound)

• Pure IO (IO bound)

• C10k

• Concurrency vs. parallelism

Warmup !

• Lazy schedule a task for later

• Avoid waiting for IO (i.e. 2x DB queries)

• Solve embarrassingly parallel problems

• Control and manage status of task

PEP index briefPEP Name Status Doc

PEP 255 Simple Generators 2.2 ✔ » »

PEP 342 Coroutines via Enhanced Generators 2.5 ✔ »

PEP 380 Syntax for Delegating to a Subgenerator 3.3 ✔ »

PEP 3148 Futures - execute computations asynchronously 3.2 ✔ »

PEP 3153 Asynchronous IO support 3.3 ✔ »

PEP 3156 Asynchronous IO Support Rebooted: the "asyncio" Module

3.4 ✔ »

PEP Name Status

PEP 219 Stackless Python ❙❙

PEP 220 Coroutines, Generators, Continuations ✗

PEP 319 Python Synchronize/Asynchronize Block ✗

PEP 3145 Asynchronous I/O For subprocess.Popen ❙❙

PEP 3152 Cofunctions ❙❙

PEP index brief

gevent

threading

asyncore

subpocesscelerypyuv

tornado

stackless

asynciotwistedeventlet

In the Class

greenlet

shed

concurrent.futures

asyncio

In the Class

gevent

threading

asyncore

subpocesscelerypyuv

tornado

stackless

asynciotwistedeventlet

In the Class

greenlet

shed

concurrent.futures

threadingsubpocess

celery

tornado

asynciotwisted

In the Classconcurrent.futures

Slang*• future ~ result wrapper

• coro != generator function (but close)

• task = coro wrapped in Future

• result = yield from future/coro (to wait for result)

new* old style concurrency

def update_foo(data): data1 = run_query1(data) data2 = run_query2(data) ! data3 = process(data1, data2) run_update_query(data3) run_update_cache(data3) ! return ["OK"]

new* old style concurrency

def update_foo(data): data1 = run_query1(data) data2 = run_query2(data) ! data3 = process(data1, data2) run_update_query(data3) run_update_cache(data3) ! return ["OK"]

new* old style concurrency

new* old style concurrency

new* old style concurrency

@asyncio.coroutine def update_foo(data, loop): data1 = yield from run_query1(data) data2 = yield from run_query2(data) ! data3 = yield from process(data1, data2) yield from run_update_query(data3) loop.call_soon(update_cache, data3) ! return ["OK"]

new* old style concurrency

@asyncio.coroutine def update_foo(data, loop): data1 = yield from run_query1(data) data2 = yield from run_query2(data) ! data3 = yield from process(data1, data2) yield from run_update_query(data3) loop.call_soon(update_cache, data3) ! return ["OK"]

new* old style concurrency

@asyncio.coroutine def update_foo(data, loop): data1 = yield from run_query1(data) data2 = yield from run_query2(data) ! data3 = yield from process(data1, data2) yield from run_update_query(data3) loop.call_soon(update_cache, data3) ! return ["OK"]

new* old style concurrency

new* old style concurrency

new* old style concurrency

new* old style concurrency

@asyncio.coroutine def update_foo(data, loop): future1 = asyncio.async(run_query1(data)) future2 = asyncio.async(run_query2(data)) ! results = yield from asyncio.gather( future1, future2) data3 = yield from process(*results) yield from run_update_query(data3) ! loop.call_soon(update_cache, data3) ! return ["OK"]

new* old style concurrency

@asyncio.coroutine def update_foo(data, loop): future1 = asyncio.async(run_query1(data)) future2 = asyncio.async(run_query2(data)) ! results = yield from asyncio.gather( future1, future2) data3 = yield from process(*results) yield from run_update_query(data3) ! loop.call_soon(update_cache, data3) ! return ["OK"]

new* old style concurrency

@asyncio.coroutine def update_foo(data, loop): future1 = asyncio.async(run_query1(data)) future2 = asyncio.async(run_query2(data)) ! results = yield from asyncio.gather( future1, future2) data3 = yield from process(*results) yield from run_update_query(data3) ! loop.call_soon(update_cache, data3) ! return ["OK"]

new* old style concurrency

new* old style concurrency

new* old style concurrency

new* old style concurrency

def api_calls(): data1 = call_api1() data2 = call_api2() data3 = call_api3() ! return [data1, data2, data3]

new* old style concurrency

def api_calls(): data1 = call_api1() data3 = call_api2() data3 = call_api3() ! return [data1, data2, data3]

new* old style concurrency

new* old style concurrency

new* old style concurrency

@asyncio.coroutine def api_calls(): future1 = asyncio.Task(call_api1()) future2 = asyncio.Task(call_api2()) future3 = asyncio.Task(call_api3()) ! return ( yield from asyncio.gather( future1, future2, future3) )

new* old style concurrency

@asyncio.coroutine def api_calls(): future1 = asyncio.Task(call_api1()) future2 = asyncio.Task(call_api2()) future3 = asyncio.Task(call_api3()) ! return ( yield from asyncio.gather( future1, future2, future3) )

new* old style concurrency

new* old style concurrency

new* old style concurrency

new* old style concurrency

from aiohttp import request !@asyncio.coroutine def call_api(): url = "URL" response = yield from request('GET', url) return (yield from response.read())

Takeaways

• concurrency patterns

• asyncio bootstrap

• early adopters

Links

Photo by Jake Brown used under CC BY 2.0/“Mono+Tile”

• Video by BDFL Tulip: Async I/O for Python 3

• Video by BDFL PyCon US 2013 Keynote

• Code by Nikolay Kim aiohttp

• Code by google appengine-pipeline

• Code by google ndb tasklets