I am opening a file which has 100,000 URL's. I need to send an HTTP request to each URL and print the status code. I am using Python 2.6, and so far looked at the many confusing ways Python implements threading/concurrency. I have even looked at the python concurrence library, but cannot figure out how to write this program correctly. Has anyone come across a similar problem? I guess generally I need to know how to perform thousands of tasks in Python as fast as possible - I suppose that means 'concurrently'.
当前回答
线程绝对不是这里的答案。它们将提供进程和内核瓶颈,以及吞吐量限制,如果总体目标是“最快的方式”,这些限制是不可接受的。
稍微扭曲一点,它的异步HTTP客户端会给你更好的结果。
其他回答
创建epoll对象, 打开许多客户端TCP套接字, 调整他们的发送缓冲区比请求头多一点, 发送一个请求头-它应该是即时的,只是放置到缓冲区, 在epoll对象中注册套接字 在epoll obect上做。poll, 从.poll中读取每个套接字的前3个字节, 将它们写入sys。Stdout后面跟着\n(不刷新), 关闭客户端套接字。
限制同时打开的套接字数量-在创建套接字时处理错误。只有当另一个套接字关闭时才创建新的套接字。 调整操作系统限制。 尝试分成几个(不是很多)进程:这可能有助于更有效地使用CPU。
我知道这是一个老问题,但在Python 3.7中,您可以使用asyncio和aiohttp来做到这一点。
import asyncio
import aiohttp
from aiohttp import ClientSession, ClientConnectorError
async def fetch_html(url: str, session: ClientSession, **kwargs) -> tuple:
try:
resp = await session.request(method="GET", url=url, **kwargs)
except ClientConnectorError:
return (url, 404)
return (url, resp.status)
async def make_requests(urls: set, **kwargs) -> None:
async with ClientSession() as session:
tasks = []
for url in urls:
tasks.append(
fetch_html(url=url, session=session, **kwargs)
)
results = await asyncio.gather(*tasks)
for result in results:
print(f'{result[1]} - {str(result[0])}')
if __name__ == "__main__":
import pathlib
import sys
assert sys.version_info >= (3, 7), "Script requires Python 3.7+."
here = pathlib.Path(__file__).parent
with open(here.joinpath("urls.txt")) as infile:
urls = set(map(str.strip, infile))
asyncio.run(make_requests(urls=urls))
你可以阅读更多关于它的内容,并在这里看到一个例子。
使用线程池是一个很好的选择,这将使这相当容易。不幸的是,python并没有一个标准库来简化线程池。但这里有一个不错的图书馆,你应该开始: http://www.chrisarndt.de/projects/threadpool/
来自他们网站的代码示例:
pool = ThreadPool(poolsize)
requests = makeRequests(some_callable, list_of_args, callback)
[pool.putRequest(req) for req in requests]
pool.wait()
希望这能有所帮助。
(下一个项目的自我提示)
Python 3解决方案只使用请求。它是最简单且快速的,不需要多处理或复杂的异步库。
最重要的方面是重用连接,特别是对于HTTPS (TLS需要额外的往返才能打开)。注意,连接是特定于子域的。如果在多个域上抓取多个页面,则可以对url列表进行排序,以最大化连接重用(它有效地按域进行排序)。
当给定足够的线程时,它将与任何异步代码一样快。(请求在等待响应时释放python GIL)。
[带有日志记录和错误处理的生产等级代码]
import logging
import requests
import time
from concurrent.futures import ThreadPoolExecutor, as_completed
# source: https://stackoverflow.com/a/68583332/5994461
THREAD_POOL = 16
# This is how to create a reusable connection pool with python requests.
session = requests.Session()
session.mount(
'https://',
requests.adapters.HTTPAdapter(pool_maxsize=THREAD_POOL,
max_retries=3,
pool_block=True)
)
def get(url):
response = session.get(url)
logging.info("request was completed in %s seconds [%s]", response.elapsed.total_seconds(), response.url)
if response.status_code != 200:
logging.error("request failed, error code %s [%s]", response.status_code, response.url)
if 500 <= response.status_code < 600:
# server is overloaded? give it a break
time.sleep(5)
return response
def download(urls):
with ThreadPoolExecutor(max_workers=THREAD_POOL) as executor:
# wrap in a list() to wait for all requests to complete
for response in list(executor.map(get, urls)):
if response.status_code == 200:
print(response.content)
def main():
logging.basicConfig(
format='%(asctime)s.%(msecs)03d %(levelname)-8s %(message)s',
level=logging.INFO,
datefmt='%Y-%m-%d %H:%M:%S'
)
urls = [
"https://httpstat.us/200",
"https://httpstat.us/200",
"https://httpstat.us/200",
"https://httpstat.us/404",
"https://httpstat.us/503"
]
download(urls)
if __name__ == "__main__":
main()
(工具)
Apache Bench是您所需要的全部。—用于测量HTTP web服务器性能的命令行计算机程序
给你一篇不错的博客文章:https://www.petefreitag.com/item/689.cfm(来自Pete Freitag)
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