Socket handshake error when using gunicorn

Question

I have a flask app that processes a web socket stream of audio from Twilio.

The app works fine without gunicorn but when I start it with gunicorn I get only the first message of the socket (connect) and an unsuccessful handshake. Here is how the app looks:

from flask import Flask
from flask_sockets import Sockets
from geventwebsocket.handler import WebSocketHandler
from gevent import pywsgi
...

app = Flask(__name__)
sockets = Sockets(app)
...
@sockets.route('/media')
def media(ws):
    ...
if __name__ == '__main__':
    server = pywsgi.WSGIServer(('', HTTP_SERVER_PORT), app, handler_class=WebSocketHandler)
    server.serve_forever()

When I start the app directly using python flaskapp.py it works ok.

When I start it using gunicorn by writing:

gunicorn -k flask_sockets.worker --bind 0.0.0.0:5055 --log-level=bug flaskapp:app

this is where the connection "hangs" and carries no further than the initial connection, apparently due to the handshake failing.

It's important to note that I haven't "gevent monkey patched" the code, but I'm not sure if it has anything to do with the problem.

Any idea will much be appreciated!

score 0 · Answer 1 · answered Jan 03 '21 at 15:19

Don't have the ability to test this right now, but perhaps try with:

from flask import Flask
from flask_sockets import Sockets
from geventwebsocket.handler import WebSocketHandler
from gevent import pywsgi
...

app = Flask(__name__)
sockets = Sockets(app)
...
@sockets.route('/media')
def media(ws):
    ...

server = pywsgi.WSGIServer(('', HTTP_SERVER_PORT), app, handler_class=WebSocketHandler)

if __name__ == '__main__':
    server.serve_forever()

Then change the launch command to:

gunicorn -k flask_sockets.worker --bind 0.0.0.0:5055 --log-level=bug flaskapp:server

(Gunicorn should be importing the server object, which can't live within that final if statement, as that code only runs when launched with python directly).

Socket handshake error when using gunicorn

1 Answers1