如何使用asyncio添加连接超时？

Question

我想非常快地连接到很多不同网站的列表.我使用asyncio以异步方式执行此操作,现在想要添加超时,以便在需要花费太长时间来响应时忽略连接.

我该如何实现？

import ssl
import asyncio
from contextlib import suppress
from concurrent.futures import ThreadPoolExecutor
import time


@asyncio.coroutine
def run():
    while True:
        host = yield from q.get()
        if not host:
            break

        with suppress(ssl.CertificateError):
            reader, writer = yield from asyncio.open_connection(host[1], 443, ssl=True) #timout option?
            reader.close()
            writer.close()


@asyncio.coroutine
def load_q():
    # only 3 entries for debugging reasons
    for host in [[1, 'python.org'], [2, 'qq.com'], [3, 'google.com']]:
        yield from q.put(host)
    for _ in range(NUM):
        q.put(None)


if __name__ == "__main__":
    NUM = 1000
    q = asyncio.Queue()

    loop = asyncio.get_event_loop()
    loop.set_default_executor(ThreadPoolExecutor(NUM))

    start = time.time()
    coros = [asyncio.async(run()) for i in range(NUM)]
    loop.run_until_complete(load_q())
    loop.run_until_complete(asyncio.wait(coros))
    end = time.time()
    print(end-start)

(旁注:有人知道如何优化这个吗？)

Answer 1

您可以将调用包装到open_connectionin中asyncio.wait_for,这允许您指定超时:

    with suppress(ssl.CertificateError):
        fut = asyncio.open_connection(host[1], 443, ssl=True)
        try:
            # Wait for 3 seconds, then raise TimeoutError
            reader, writer = yield from asyncio.wait_for(fut, timeout=3)
        except asyncio.TimeoutError:
            print("Timeout, skipping {}".format(host[1]))
            continue

请注意,在TimeoutError引发时,open_connection协程也会被取消.如果您不希望它被取消(虽然我认为您确实希望在这种情况下取​​消它),您已将呼叫包裹起来asyncio.shield.