为什么asyncio不总是使用执行程序？

我必须发送很多HTTP请求，一旦它们全部返回，程序就可以继续。听起来像是完美的搭配asyncio。天真地，我将to的调用包装requests在一个async函数中，然后将它们交给asyncio。这行不通。

在网上搜索后，我发现了两种解决方案：

• 使用像aiohttp这样的库，该库可以与asyncio
• 将阻塞代码包装为 run_in_executor

为了更好地理解这一点，我编写了一个小型基准。服务器端是一个Flask程序，它在响应请求之前等待0.1秒。

from flask import Flask
import time

app = Flask(__name__)


@app.route('/')
def hello_world():
    time.sleep(0.1) // heavy calculations here :)
    return 'Hello World!'


if __name__ == '__main__':
    app.run()

客户是我的基准

import requests
from time import perf_counter, sleep

# this is the baseline, sequential calls to requests.get
start = perf_counter()
for i in range(10):
    r = requests.get("http://127.0.0.1:5000/")
stop = perf_counter()
print(f"synchronous took {stop-start} seconds") # 1.062 secs

# now the naive asyncio version
import asyncio
loop = asyncio.get_event_loop()

async def get_response():
    r = requests.get("http://127.0.0.1:5000/")

start = perf_counter()
loop.run_until_complete(asyncio.gather(*[get_response() for i in range(10)]))
stop = perf_counter()
print(f"asynchronous took {stop-start} seconds") # 1.049 secs

# the fast asyncio version
start = perf_counter()
loop.run_until_complete(asyncio.gather(
    *[loop.run_in_executor(None, requests.get, 'http://127.0.0.1:5000/') for i in range(10)]))
stop = perf_counter()
print(f"asynchronous (executor) took {stop-start} seconds") # 0.122 secs

#finally, aiohttp
import aiohttp

async def get_response(session):
    async with session.get("http://127.0.0.1:5000/") as response:
        return await response.text()

async def main():
    async with aiohttp.ClientSession() as session:
        await get_response(session)

start = perf_counter()
loop.run_until_complete(asyncio.gather(*[main() for i in range(10)]))
stop = perf_counter()
print(f"aiohttp took {stop-start} seconds") # 0.121 secs

因此，具有的直观实现asyncio无需处理阻塞io代码。但是，如果使用asyncio正确，它与特殊aiohttp框架一样快。协程和任务的文档并没有真正提到这一点。仅当您阅读loop.run_in_executor（）时，它才会说：

# File operations (such as logging) can block the
# event loop: run them in a thread pool.

我对此行为感到惊讶。异步的目的是加快阻塞io调用。为什么需要一个额外的包装器run_in_executor来做到这一点？

的整个卖点aiohttp似乎是对的支持asyncio。但据我所知，requests只要您将其包装在执行程序中，该模块就可以完美运行。是否有理由避免将某些东西包装在执行器中？