emit() does not work sometimes

[LostInDarkMath]

Hi there,
I try to call emit() in a socketio.start_background_task(), but it does not work with the client. My code is based on https://github.com/miguelgrinberg/Flask-SocketIO-Chat and looks like this:

from flask import Flask
from flask_socketio import SocketIO, emit

socketio = SocketIO()


def _background():
    while True:
        print('cycle sync')
        time.sleep(5)
        socketio.emit(event='message', data={"msg": f"Bot:FOOOO!"})

def create_app() -> Flask:
    app = Flask(__name__)
    app.debug = True
    app.config['SECRET_KEY'] = 'secret'

   # ...

    socketio.init_app(
        app=app,
        path="/ws/socket.io",
        cors_allowed_origins="*",
        logger=True,
        engineio_logger=True,
        async_mode='gevent_uwsgi',
    )
    socketio.start_background_task(_background)
    return app

events.py:

from flask import session
from flask_socketio import emit, join_room, leave_room
from .. import socketio


@socketio.on('joined', namespace='/chat')
def joined(message) -> None:
    """
        Sent by clients when they enter a room.
        A status message is broadcast to all people in the room.
    """

    print(f'JOINED: {message}')
    room = session.get('room')
    join_room(room)
    emit('status', {'msg': session.get('name') + ' has entered the room.'}, room=room)


@socketio.on('text', namespace='/chat')
def text(message) -> None:
    """
        Sent by a client when the user entered a new message.
        The message is sent to all people in the room.
    """

    room = session.get('room')
    print('TEXT', room, message)
    emit('message', {'msg': session.get('name') + ':' + message['msg']}, room=room)


@socketio.on('left', namespace='/chat')
def left(message) -> None:
    """
        Sent by clients when they leave a room.
        A status message is broadcast to all people in the room.
    """

    room = session.get('room')
    leave_room(room)
    emit('status', {'msg': session.get('name') + ' has left the room.'}, room=room)


@socketio.on_error()
def on_error_default(message) -> None:
    print(f'ON ERROR: {message}')

run.py:

from gevent import monkey
monkey.patch_all()

from websockets.app import create_app

app = create_app()

Description

The chat works completly fine, but the SockeIO events that are emitted from the background task are not received in the frontend. But the library debug logs of your library tell me, that those events were emitted correctly.

Logs

websocket_gateway_1  | nz74-cLL-jKeFmM2AAAC: Received packet MESSAGE data 2/chat,["text",{"msg":"dsfghg"}]  <-- manual chat message works
websocket_gateway_1  | received event "text" from Dfxa1C4rUAHH3sOXAAAD [/chat]
websocket_gateway_1  | TEXT 1 {'msg': 'dsfghg'}
websocket_gateway_1  | emitting event "message" to 1 [/chat]
websocket_gateway_1  | nz74-cLL-jKeFmM2AAAC: Sending packet MESSAGE data 2/chat,["message",{"msg":"Willi:dsfghg"}]
websocket_gateway_1  | emitting event "message" to all [/]
websocket_gateway_1  | cycle sync
websocket_gateway_1  | emitting event "message" to all [/]  <-- background chat message does not work
websocket_gateway_1  | cycle sync

Do you have an idea what's the issue here?

[miguelgrinberg]

The emit is working fine, but you are using a different namespace. Try adding the correct namespace:

socketio.emit(event='message', data={"msg": f"Bot:FOOOO!"}, namespace='/chat')

[LostInDarkMath]

Oh my god, thank you!