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xiongshengyao
V2EX  ›  Python

新手尝试用 aiohttp 写了个爬虫,但是目前因为 task 过多(超过 1000 个),报错 Too many open files,请问如何解决呢?

  •  
  •   xiongshengyao · 2018-03-19 09:49:10 +08:00 · 8553 次点击
    这是一个创建于 2442 天前的主题,其中的信息可能已经有所发展或是发生改变。

    完整代码

    import time
    import asyncio
    
    import aiohttp
    from bs4 import BeautifulSoup as bs
    
    BASE_URL = "http://www.biqudu.com"
    TITLE2URL = dict()
    CONTENT = list()
    
    
    async def fetch(url, callback=None, **kwarags):
        headers = {'User-Agent':'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'}
        sem = asyncio.Semaphore(5)  
        with (await sem):
            async with aiohttp.ClientSession() as session: 
                async with session.get(url, headers=headers) as res:
                    page = await res.text()
                    if callback:
                        callback(page, **kwarags)
                    else:
                        return page
    
    
    def parse_url(page):
        soup = bs(page, "lxml")
        dd_a_doc = soup.select("dd > a")
        for a_doc in dd_a_doc:
            article_page_url = a_doc['href']
            article_title = a_doc.get_text()
            if article_page_url:
                TITLE2URL[article_title] = article_page_url
    
    
    def parse_body(page, **kwarags):
        title = kwarags.get('title', '')
        print("{}".format(title))
        soup = bs(page, "lxml")
        content_doc = soup.find("div", id="content")
        content_text = content_doc.get_text().replace('readx();', '').replace('    ', "\r\n")
        content = "%s\n%s\n\n" % (title, content_text)
        CONTENT.append(content)
    
    
    def main():
        t0 = time.time()
        loop = asyncio.get_event_loop()
        loop.run_until_complete(fetch(BASE_URL+"/43_43074/", callback=parse_url))
        tasks = [fetch(BASE_URL + page_url, callback=parse_body, title=title) for title, page_url in TITLE2URL.items()]
        loop.run_until_complete(asyncio.gather(*tasks[:500]))
        loop.close()
        elapsed = time.time() - t0
        print("cost {}".format(elapsed))
    
    
    if __name__ == "__main__":
        main()
    

    错误信息

    Traceback (most recent call last):
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/connector.py", line 797, in _wrap_create_connection
        return (yield from self._loop.create_connection(*args, **kwargs))
      File "/usr/lib/python3.5/asyncio/base_events.py", line 695, in create_connection
        raise exceptions[0]
      File "/usr/lib/python3.5/asyncio/base_events.py", line 662, in create_connection
        sock = socket.socket(family=family, type=type, proto=proto)
      File "/usr/lib/python3.5/socket.py", line 134, in __init__
        _socket.socket.__init__(self, family, type, proto, fileno)
    OSError: [Errno 24] Too many open files
    
    The above exception was the direct cause of the following exception:
    
    Traceback (most recent call last):
      File "/home/xsy/Workspace/Self/aiotest/aiotest.py", line 58, in <module>
        main()
      File "/home/xsy/Workspace/Self/aiotest/aiotest.py", line 52, in main
        loop.run_until_complete(asyncio.gather(*tasks[:500]))
      File "/usr/lib/python3.5/asyncio/base_events.py", line 387, in run_until_complete
        return future.result()
      File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
        raise self._exception
      File "/usr/lib/python3.5/asyncio/tasks.py", line 239, in _step
        result = coro.send(None)
      File "/home/xsy/Workspace/Self/aiotest/aiotest.py", line 18, in fetch
        async with session.get(url, headers=headers) as res:
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/client.py", line 690, in __aenter__
        self._resp = yield from self._coro
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/client.py", line 267, in _request
        conn = yield from self._connector.connect(req)
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/connector.py", line 402, in connect
        proto = yield from self._create_connection(req)
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/connector.py", line 749, in _create_connection
        _, proto = yield from self._create_direct_connection(req)
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/connector.py", line 860, in _create_direct_connection
        raise last_exc
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/connector.py", line 832, in _create_direct_connection
        req=req, client_error=client_error)
      File "/usr/local/lib/python3.5/dist-packages/aiohttp/connector.py", line 804, in _wrap_create_connection
        raise client_error(req.connection_key, exc) from exc
    aiohttp.client_exceptions.ClientConnectorError: Cannot connect to host www.biqudu.com:443 ssl:True [Too many open files]
    

    目前我能想到的方法是

    • 修改 linux 的最大文件打开数量限制
    • 对 task 切片多次运行

    但是这样解决都感觉太蠢了,请问有什么更好的方式吗?

    15 条回复    2018-09-21 10:46:49 +08:00
    WuMingyu
        1
    WuMingyu  
       2018-03-19 10:04:40 +08:00 via iPhone
    考虑下多个请求共同一个 client session,一个 clientsession 至少会占用一个链接的
    WuMingyu
        2
    WuMingyu  
       2018-03-19 10:07:33 +08:00 via iPhone
    xiongshengyao
        3
    xiongshengyao  
    OP
       2018-03-19 10:10:54 +08:00
    @WuMingyu 好哒,我试试
    janxin
        4
    janxin  
       2018-03-19 10:14:20 +08:00
    linux 打开文件句柄上限了解一下?
    zhengwenk
        5
    zhengwenk  
       2018-03-19 10:15:35 +08:00
    Too many open files 的话不是应该将最大文件数修改大一些么
    xiongshengyao
        6
    xiongshengyao  
    OP
       2018-03-19 10:16:30 +08:00
    @janxin 了解了,确实可以,但是觉得这种解决方式不优雅…
    ipwx
        7
    ipwx  
       2018-03-19 10:17:14 +08:00
    其实我对你这两句话表示疑惑:

    sem = asyncio.Semaphore(5)
    with (await sem):

    请问你是要靠 Semaphore 控制并发嘛?可是每个 fetch 用一个独立的 Semaphore 你靠什么去控制并发呢?
    xiongshengyao
        8
    xiongshengyao  
    OP
       2018-03-19 10:17:41 +08:00
    @zhengwenk 治标不治本呢…现在这个是链接是 1000 多…下次爬的假如是 10000 岂不是又要改…我按一楼的改好了…
    ipwx
        9
    ipwx  
       2018-03-19 10:18:57 +08:00
    另外 @WuMingyu 说的那一点也是,你为什么每一个 fetch 都用一个独立的 ClientSession 呢?

    事实上 Semaphore 或者 ClientSession 两者之中任何一个都能控制并发。Semaphore 可以控制同时运行的 task,而 ClientSession 可以控制最大连接数(当然你得加参数)。当然你必须用同一个对象才行。
    lfzyx
        10
    lfzyx  
       2018-03-19 10:19:37 +08:00
    这有什么优雅不优雅的,每个发行版的初始 open files 限制都不一样,而在云上的话,早就被云供应商改成 65535 甚至更高了
    xiongshengyao
        11
    xiongshengyao  
    OP
       2018-03-19 10:23:21 +08:00
    @ipwx
    @lfzyx
    @zhengwenk
    @janxin
    @WuMingyu
    感谢各位,已经有个解决的思路了,谢谢大家~~~
    CSM
        12
    CSM  
       2018-03-19 10:27:05 +08:00 via Android
    楼上说得对,aiohttp 文档中说一个 app 只需要一个 ClientSession 就够了。可以把 session 作为 fetch 的一个参数。
    bestehen
        13
    bestehen  
       2018-06-17 19:04:00 +08:00
    @xiongshengyao 我看你这里 task 是 500 个啊,怎么是 1000 个 *tasks[:500]))
    handan
        14
    handan  
       2018-09-20 17:50:30 +08:00
    可以问一下,你之前你这个问题有想到什么好的 解决方案么??
    xiongshengyao
        15
    xiongshengyao  
    OP
       2018-09-21 10:46:49 +08:00   ❤️ 1
    @handan   1 楼
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