Python并发编程队列与多线程最快发送http请求方式

编辑: admin 分类: python 发布时间: 2021-12-03 来源:互联网

队列+多线程

定义一个大小为 400 的队列，然后开启 200 个线程，每个线程都是不断的从队列中获取 url 并访问。

主线程读取文件中的 url 放入队列中，然后等待队列中所有的元素都被接收和处理完毕。代码如下：

from threading import Thread
import sys
from queue import Queue
import requests
concurrent = 200 
def doWork():
    while True:
        url = q.get()
        status, url = getStatus(url)
        doSomethingWithResult(status, url)
        q.task_done()
def getStatus(ourl):
    try:
        res = requests.get(ourl)
        return res.status_code, ourl
    except:
        return "error", ourl
def doSomethingWithResult(status, url):
    print(status, url) 
q = Queue(concurrent * 2)
for i in range(concurrent):
    t = Thread(target=doWork)
    t.daemon = True
    t.start() 
try:
    for url in open("urllist.txt"):
        q.put(url.strip())
    q.join()
except KeyboardInterrupt:
    sys.exit(1)

运行结果如下：

有没有 get 到新技能？

线程池

如果你使用线程池，推荐使用更高级的 concurrent.futures 库：

import concurrent.futures
import requests
out = []
CONNECTIONS = 100
TIMEOUT = 5
urls = []
with open("urllist.txt") as reader:
    for url in reader:
        urls.append(url.strip())
def load_url(url, timeout):
    ans = requests.get(url, timeout=timeout)
    return ans.status_code
with concurrent.futures.ThreadPoolExecutor(max_workers=CONNECTIONS) as executor:
    future_to_url = (executor.submit(load_url, url, TIMEOUT) for url in urls)
    for future in concurrent.futures.as_completed(future_to_url):
        try:
            data = future.result()
        except Exception as exc:
            data = str(type(exc))
        finally:
            out.append(data)
            print(data)

协程 + aiohttp

协程也是并发非常常用的工具了：

import asyncio
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 sys
    assert sys.version_info >= (3, 7), "Script requires Python 3.7+."
    with open("urllist.txt") as infile:
        urls = set(map(str.strip, infile))
    asyncio.run(make_requests(urls=urls))

grequests

这是个第三方库，目前有 3.8K 个星，就是 Requests + Gevent，让异步 http 请求变得更加简单。Gevent 的本质还是协程。

使用前：

pip install grequests

使用起来那是相当的简单：

import grequests
urls = []
with open("urllist.txt") as reader:
    for url in reader:
        urls.append(url.strip())
rs = (grequests.get(u) for u in urls)
for result in grequests.map(rs):
    print(result.status_code, result.url)

注意 grequests.map(rs) 是并发执行的。运行结果如下：

也可以加入异常处理：

>>> def exception_handler(request, exception):
...    print("Request failed")
>>> reqs = [
...    grequests.get('http://httpbin.org/delay/1', timeout=0.001),
...    grequests.get('http://fakedomain/'),
...    grequests.get('http://httpbin.org/status/500')]
>>> grequests.map(reqs, exception_handler=exception_handler)
Request failed
Request failed
[None, None, <Response [500]>]

最后的话

今天分享了并发 http 请求的几种实现方式，有人说异步（协程）性能比多线程好，其实要分场景看的，没有一种方法适用所有的场景，笔者就曾做过一个实验，也是请求 url，当并发数量超过 500 时，协程明显变慢。

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Python并发编程队列与多线程最快发送http请求方式

目录

队列+多线程

线程池

协程 + aiohttp

grequests

最后的话