I want to serve my Flask app with a ASGI server called Uvicorn. Turns out when I convert my app from wsgi to asgi (following instructions here https://flask.palletsprojects.com/en/2.0.x/deploying/asgi/) suddently app.logger function is undefined. But I really need the logging functionality to develop my app.
Please follow the steps below to reproduce the problem.
I wrote this basic app
from flask import Flask
from asgiref.wsgi import WsgiToAsgi
app = Flask(__name__)
@app.route("/")
def hello_world():
app.logger.info("hey I am your favourite log message")
return "<p>Hello, World!</p>"
app = WsgiToAsgi(app)
I installed uvicorn
pip install uvicorn
Ran my app
uvicorn app:app
And I get this error when the app tries to log using app.logger
ERROR: Exception in ASGI application
Traceback (most recent call last):
File "f:\projects\logger-flask\venv\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 373, in run_asgi
result = await app(self.scope, self.receive, self.send)
File "f:\projects\logger-flask\venv\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 75, in __call__
return await self.app(scope, receive, send)
File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\wsgi.py", line 21, in __call__
await WsgiToAsgiInstance(self.wsgi_application)(scope, receive, send)
File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\wsgi.py", line 51, in __call__
await self.run_wsgi_app(body)
File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\sync.py", line 444, in __call__
ret = await asyncio.wait_for(future, timeout=None)
File "C:\Users\Tamjid\AppData\Local\Programs\Python\Python38\lib\asyncio\tasks.py", line 455, in wait_for
return await fut
File "C:\Users\Tamjid\AppData\Local\Programs\Python\Python38\lib\concurrent\futures\thread.py", line 57, in run
result = self.fn(*self.args, **self.kwargs)
File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\sync.py", line 486, in thread_handler
return func(*args, **kwargs)
File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\wsgi.py", line 140, in run_wsgi_app
for output in self.wsgi_application(environ, self.start_response):
File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 2088, in __call__
return self.wsgi_app(environ, start_response)
File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 2073, in wsgi_app
response = self.handle_exception(e)
File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 2070, in wsgi_app
response = self.full_dispatch_request()
File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 1515, in full_dispatch_request
rv = self.handle_user_exception(e)
File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 1513, in full_dispatch_request
rv = self.dispatch_request()
File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 1499, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
File ".\app.py", line 8, in hello_world
app.logger.info("hey I am your favourite log message")
AttributeError: 'WsgiToAsgi' object has no attribute 'logger'
An instance of Flask supports the WSGI protocol, and it also adds a number of conveniences, such as a logger. If you wrap the Flask instance and lose the reference to it, you lose those convenience methods.
Instead of
app = WsgiToAsgi(app)
try
wsgi = WsgiToAsgi(app)
then
uvicorn app:wsgi