Flask 2.x running on asyncio!
Is there a purpose for this, now that Flask 2.0 is out with support for async views? Yes! Flask's own support for async handlers is very limited, as the application still runs inside a WSGI web server, which severely limits scalability. With aioflask you get a true ASGI application, running in a 100% async environment.
WARNING: This is an experiment at this point. Not at all production ready!
To use async view functions and other handlers, use the aioflask package
instead of flask.
The aioflask.Flask class is a subclass of flask.Flask that changes a few
minor things to help the application run properly under the asyncio loop. In
particular, it overrides the following aspects of the application instance:
- The
route,before_request,before_first_request,after_request,teardown_request,teardown_appcontext,errorhandlerandcli.commanddecorators accept coroutines as well as regular functions. The handlers all run inside an asyncio loop, so when using regular functions, care must be taken to not block. - The WSGI callable entry point is replaced with an ASGI equivalent.
- The
run()method uses uvicorn as web server.
There are also changes outside of the Flask class:
- The
flask aioruncommand starts an ASGI application using the uvicorn web server. - The
render_template()andrender_template_string()functions are asynchronous and must be awaited. - The context managers for the Flask application and request contexts are async.
- The test client and test CLI runner use coroutines.
import asyncio
from aioflask import Flask, render_template
app = Flask(__name__)
@app.route('/')
async def index():
await asyncio.sleep(1)
return await render_template('index.html')