How to solve ValueError('Invalid async_mode specified') for flask-socketio? - socket.io

Question

I'm testing a flask-socketio server in bitbucket pipeline. It failed with the following messages:
Traceback (most recent call last):
File "/root/.local/share/virtualenvs/build-3vGKWv3F/lib/python3.7/site-packages/flask_failsafe.py", line 29, in wrapper
return func(*args, **kwargs)
File "/opt/atlassian/pipelines/agent/build/main.py", line 89, in create_app
return cell_data_api.create_app()
File "/opt/atlassian/pipelines/agent/build/cell_data_api/__init__.py", line 30, in create_app
socketio.init_app(app)
File "/root/.local/share/virtualenvs/build-3vGKWv3F/lib/python3.7/site-packages/flask_socketio/__init__.py", line 243, in init_app
self.server = socketio.Server(**self.server_options)
File "/root/.local/share/virtualenvs/build-3vGKWv3F/lib/python3.7/site-packages/socketio/server.py", line 127, in __init__
self.eio = self._engineio_server_class()(**engineio_options)
File "/root/.local/share/virtualenvs/build-3vGKWv3F/lib/python3.7/site-packages/engineio/server.py", line 145, in __init__
raise ValueError('Invalid async_mode specified')
ValueError: Invalid async_mode specified
Traceback (most recent call last):
File "/.pyenv/versions/3.7.4/lib/python3.7/runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "/.pyenv/versions/3.7.4/lib/python3.7/runpy.py", line 85, in _run_code
exec(code, run_globals)
File "/opt/atlassian/pipelines/agent/build/main.py", line 117, in <module>
socketio.run(APP, host='0.0.0.0', port=8080, debug=True, use_reloader=True)
File "/root/.local/share/virtualenvs/build-3vGKWv3F/lib/python3.7/site-packages/flask_socketio/__init__.py", line 564, in run
if app.debug and self.server.eio.async_mode != 'threading':
AttributeError: 'NoneType' object has no attribute 'eio'
My main.py file looks like:
import os
from cell_data_api import socketio
# Detect if we are running in App Engine
# Make sure this does NOT start if we are running a Cloud Function
if os.getenv('APP_ENGINE', '') == 'TRUE':
import cell_data_api
APP = cell_data_api.create_app()
if __name__ == '__main__':
from flask_failsafe import failsafe
#failsafe
def create_app():
# note that the import is *inside* this function so that we can catch
# errors that happen at import time
import cell_data_api
# If `entrypoint` is not defined in app.yaml, App Engine will look for an app
# called `app` in `main.py`.
return cell_data_api.create_app()
APP = create_app()
# This is used when running locally only. When deploying to Google App
# Engine, a webserver process such as Gunicorn will serve the app. This
# can be configured by adding an `entrypoint` to app.yaml.
socketio.run(APP, host='0.0.0.0', port=8080, debug=True, use_reloader=True)
Main.py imports from cell_data_api.py, which looks like:
import os
from flask import Flask
from flask_cors import CORS
# import eventlet
from engineio.async_drivers import eventlet
from flask_socketio import SocketIO
socketio = SocketIO(
always_connect=True,
logger=True,
async_mode=eventlet,
cookie=...,
ping_timeout=...
)
def create_app():
# create and configure the app
app = Flask(__name__)
CORS(app)
......
socketio.init_app(app)
# ensure the instance folder exists
try:
os.makedirs(app.instance_path)
except OSError:
pass
return app
My environment is Python 3.7 with installation packages:
[dev-packages]
alembic = "*"
flask_failsafe = "*"
wcwidth = "*"
[packages]
flask = "*"
absl-py = "*"
flask-cors = "*"
grpcio = "*"
transitions = "*"
sqlalchemy-json = "*"
sqlalchemy = "1.3.0"
flask_socketio='*'
eventlet='*'
Unlike the other two questions I found about the same error, I'm not using pyinstaller or cx_Freeze.

Answer 1

The async_mode parameter takes a string as an argument.
Instead of this:
async_mode=eventlet,
Do this:
async_mode='eventlet',