Flask asyncio aiohttp - RuntimeError: There is no current event loop in thread 'Thread-2'

Question

最近一直在阅读 python 并发性 realpython - python concurrency

我的主要关注点asyncio所以还很新。

使用 asyncio 和 aiohttp 运行执行异步活动的代码块在直接运行时没问题。

然而，当我将代码添加到我的烧瓶蓝图时，它引发了这个错误：

RuntimeError: There is no current event loop in thread 'Thread-2'

出于演示目的，我制作了一个演示烧瓶应用程序。以防有人想测试一下。

main.py

from flask import Flask
from my_blueprint import my_blueprint

#Define flask app
app = Flask(__name__)

#load blueprints
app.register_blueprint(my_blueprint,url_prefix='/demo')

#start flask
if __name__ == '__main__':
    app.run(debug=True)

my_blueprint.py

from flask import Blueprint,request, jsonify,abort,make_response
from flask import make_response
import asyncio
import time
import aiohttp

my_blueprint = Blueprint('my_blueprint', __name__)

@my_blueprint.route('/',methods=['GET'])
def home():
    #code block
    async def download_site(session, url):
        async with session.get(url) as response:
            print("Read {0} from {1}".format(response.content_length, url))


    async def download_all_sites(sites):
        async with aiohttp.ClientSession() as session:
            tasks = []
            for url in sites:
                task = asyncio.ensure_future(download_site(session, url))
                tasks.append(task)
            await asyncio.gather(*tasks, return_exceptions=True)

    sites = ["https://www.jython.org","http://olympus.realpython.org/dice"]*20
    start_time = time.time()
    asyncio.get_event_loop().run_until_complete(download_all_sites(sites))
    duration = time.time() - start_time
    return jsonify({"status":f"Downloaded {len(sites)} sites in {duration} seconds"})
    #end of code block

Answer 1

编辑：看起来你的代码是正确的。我习惯写不同的。但是你大概是运行windows和python3.8。刚刚更改了 python 3.8 和 windows 中的默认事件循环策略，而且它有很多错误。您可以改回旧的事件循环策略：

变化：

asyncio.get_event_loop().run_until_complete(download_all_sites(sites))

进入：

asyncio.set_event_loop(asyncio.SelectorEventLoop())
asyncio.get_event_loop().run_until_complete(download_all_sites(sites))

Flask asyncio aiohttp - RuntimeError: There is no current event loop in thread 'Thread-2'

Flask asyncio aiohttp - RuntimeError: There is no current event loop in thread 'Thread-2'

python

multithreading

flask

python-asyncio

aiohttp