如何防止 raise asyncio.TimeoutError 并继续循环

Question

我正在使用带有 limited_as_completed 方法的 aiohttp 来加速抓取（大约 1 亿个静态网站页面）。但是，代码在几分钟后停止，并且 returns TimeoutError。我尝试了几种方法，但仍然无法阻止加注 asyncio.TimeoutError。请问如何忽略错误，继续？

我运行的代码是：

N=123
import html
from lxml import etree
import requests
import asyncio 
import aiohttp
from aiohttp import ClientSession, TCPConnector
import pandas as pd
import re 
import csv 
import time
from itertools import islice
import sys
from contextlib import suppress

start = time.time()
data = {}
data['name'] = []
filename = "C:\Users\xxxx"+ str(N) + ".csv"

def limited_as_completed(coros, limit):
    futures = [
        asyncio.ensure_future(c)
        for c in islice(coros, 0, limit)
    ]
    async def first_to_finish():
        while True:
            await asyncio.sleep(0)
            for f in futures:
                if f.done():
                    futures.remove(f)
                    try:
                        newf = next(coros)
                        futures.append(
                            asyncio.ensure_future(newf))
                    except StopIteration as e:
                        pass
                    return f.result()
    while len(futures) > 0:
        yield first_to_finish()

async def get_info_byid(i, url, session):
    async with session.get(url,timeout=20) as resp:
        print(url)
        with suppress(asyncio.TimeoutError):
            r = await resp.text()
            name = etree.HTML(r).xpath('//h2[starts-with(text(),"Customer Name")]/text()')
            data['name'].append(name)
            dataframe = pd.DataFrame(data)
            dataframe.to_csv(filename, index=False, sep='|')

limit = 1000
async def print_when_done(tasks):
    for res in limited_as_completed(tasks, limit):
        await res

url = "http://xxx.{}.html"
loop = asyncio.get_event_loop()

async def main():
    connector = TCPConnector(limit=10)
    async with ClientSession(connector=connector,headers=headers,raise_for_status=False) as session:
        coros = (get_info_byid(i, url.format(i), session) for i in range(N,N+1000000))
        await print_when_done(coros)

loop.run_until_complete(main())
loop.close()
print("took", time.time() - start, "seconds.")

错误日志为：

Traceback (most recent call last):
  File "C:\Users\xxx.py", line 111, in <module>
    loop.run_until_complete(main())
  File "C:\Users\xx\AppData\Local\Programs\Python\Python37-32\lib\asyncio\base_events.py", line 573, in run_until_complete
    return future.result()
  File "C:\Users\xxx.py", line 109, in main
    await print_when_done(coros)
  File "C:\Users\xxx.py", line 98, in print_when_done
    await res
  File "C:\Users\xxx.py", line 60, in first_to_finish
    return f.result()
  File "C:\Users\xxx.py", line 65, in get_info_byid
    async with session.get(url,timeout=20) as resp:
  File "C:\Users\xx\AppData\Local\Programs\Python\Python37-32\lib\site-packages\aiohttp\client.py", line 855, in __aenter__
    self._resp = await self._coro
  File "C:\Users\xx\AppData\Local\Programs\Python\Python37-32\lib\site-packages\aiohttp\client.py", line 391, in _request
    await resp.start(conn)
  File "C:\Users\xx\AppData\Local\Programs\Python\Python37-32\lib\site-packages\aiohttp\client_reqrep.py", line 770, in start
    self._continue = None
  File "C:\Users\xx\AppData\Local\Programs\Python\Python37-32\lib\site-packages\aiohttp\helpers.py", line 673, in __exit__
    raise asyncio.TimeoutError from None
concurrent.futures._base.TimeoutError

我试过了 1）添加期望asyncio.TimeoutError：通过。不工作

async def get_info_byid(i, url, session):
    async with session.get(url,timeout=20) as resp:
        print(url)
        try:
            r = await resp.text()
            name = etree.HTML(r).xpath('//h2[starts-with(text(),"Customer Name")]/text()')
            data['name'].append(name)
            dataframe = pd.DataFrame(data)
            dataframe.to_csv(filename, index=False, sep='|')
        except asyncio.TimeoutError:
            pass

2) 抑制(asyncio.TimeoutError)如上所示。不工作

我昨天刚学了aiohttp，所以我的代码可能还有其他问题导致几分钟后才出现超时错误运行？如果有人知道如何处理，非常感谢！

Answer 1

简单示例（不是很好，但工作正常）：

import asyncio
from aiohttp.client import ClientSession


class Wrapper:

    def __init__(self, session):
        self._session = session

    async def get(self, url):
        try:
            async with self._session.get(url, timeout=20) as resp:
                return await resp.text()
        except Exception as e:
            print(e)


loop = asyncio.get_event_loop()
wrapper = Wrapper(ClientSession())

responses = loop.run_until_complete(
    asyncio.gather(
        wrapper.get('http://google.com'),
        wrapper.get('http://google.com'),
        wrapper.get('http://google.com'),
        wrapper.get('http://google.com'),
        wrapper.get('http://google.com')
    )
)

print(responses)

Answer 2

@Yurii Kramarenko 所做的肯定会引发 未关闭的客户端会话异常，因为会话从未正确关闭过。我推荐的是这样的：

import asyncio
import aiohttp

async def main(urls):
    async with aiohttp.ClientSession(timeout=self.timeout) as session:
        tasks=[self.do_something(session,url) for url in urls]
        await asyncio.gather(*tasks)

Answer 3

我喜欢@jbxiaoyu 的回答，但是 timeout kwarg 似乎需要一个特殊的对象，所以我想我会添加你需要创建一个 ClientTimeout 对象，然后将它传递给 Session，如下所示：

from aiohttp import ClientSession, ClientTimeout
timeout = ClientTimeout(total=600)
async with ClientSession(timeout=timeout) as session:
    tasks=[self.do_something(session,url) for url in urls]
    await asyncio.gather(*tasks)

如何防止 raise asyncio.TimeoutError 并继续循环

How to prevent raise asyncio.TimeoutError and continue the loop

python

exception-handling

python-asyncio

aiohttp

timeoutexception