message received but the handle was not triggered

[lylanfree]

I used the class namespace-based method to register a handle to the event, and I encountered the following problem when using it

After starting the server first, and then accessing from the web page, I saw from the server logs that the message had arrived at the server, but its corresponding handler was not triggered, and after I restarted the server, I was able to trigger the handler corresponding to the event, and once I refreshed the webpage and re-established the websocket connection, server could not trigger the handler, which has been bothering me for several days

Code snippets

# socket.py
class TerminalNamespace(Namespace):
    def __init__(self, path):
        super().__init__(path)
        self.path = path
        self.sessionmanager = SessionManager(path)
    
    def on_connect(self, socket):
        if socket and socket.get('Authorization'):
            token = socket.get('Authorization')
            try:
                t = decode_token(token[7:])['sub']
                if check_admin_role(t):
                    print('check passed')
                    return
            except Exception as e:
                print(e)
        SessionManager.error({'code': 403, 'msg': 'Invalid token'}, path = self.path, to = request.sid)
 
    def on_error(self, e):
        print(e)
        
    def on_shell(self, data: dict):
        action = data.get('action')
        pid = data.get('pid')
        cid = data.get('cid')
        print('on shell', data)
        if action == 'start':
            self.sessionmanager.new_shell(request.sid, pid, cid)
        elif action == 'stop':
            self.sessionmanager.remove_shell(pid)
    def on_message(self, data: dict):
        msg = data.get('msg')
        pid = data.get('pid')
        shell = self.sessionmanager.get_shell(pid)
        if shell:
            shell.pty_input(msg)

    def on_resize(self, data: dict):
        pid = data.get('pid')
        msg = data.get('msg')
        shell = self.sessionmanager.get_shell(pid)
        if shell:
            shell.resize(msg)

# app.py
from flask import Flask
from flask_socketio import SocketIO
app = Flask('MYAPP')
socketio = SocketIO()
socketio.init(app)
socketio.on_namespace(TerminalNamespace('/terminal'))

Some logs

The logs that are properly handled are as follows

e1guDYwAPdZLnEDQAAAA: Sending packet OPEN data {'sid': 'e1guDYwAPdZLnEDQAAAA', 'upgrades': [], 'pingTimeout': 20000, 'pingInterval': 25000}
e1guDYwAPdZLnEDQAAAA: Received request to upgrade to websocket
e1guDYwAPdZLnEDQAAAA: Upgrade to websocket successful
e1guDYwAPdZLnEDQAAAA: Received packet MESSAGE data 0/terminal,{"Authorization":"Bearer xxxxxxxxx"}
check passed
e1guDYwAPdZLnEDQAAAA: Sending packet MESSAGE data 0/terminal,{"sid":"O877ogJUcP8FClXhAAAB"}
e1guDYwAPdZLnEDQAAAA: Received packet MESSAGE data 2/terminal,["shell",{"action":"start","cid":"d026bb907fa5","pid":"1721288587434"}]
on shell {'action': 'start', 'cid': 'd026bb907fa5', 'pid': '1721288587434'}
e1guDYwAPdZLnEDQAAAA: Received packet MESSAGE data 2/terminal,["resize",{"pid":"1721288587434","msg":{"rows":22,"cols":75}}]
e1guDYwAPdZLnEDQAAAA: Sending packet MESSAGE data 2/terminal,["message","{\"pid\": \"1721288587434\", \"msg\": \"Connection established\\r\\n\", \"new_id\": \"cdab99d1-8a29-4e3b-8ac8-452836ea9681\"}"]
e1guDYwAPdZLnEDQAAAA: Sending packet MESSAGE data 2/terminal,["message","{\"pid\": \"cdab99d1-8a29-4e3b-8ac8-452836ea9681\", \"msg\": \"root@d026bb907fa5:/# \"}"]
e1guDYwAPdZLnEDQAAAA: Received packet MESSAGE data 2/terminal,["shell",{"action":"stop","pid":"cdab99d1-8a29-4e3b-8ac8-452836ea9681"}]
on shell {'action': 'stop', 'pid': 'cdab99d1-8a29-4e3b-8ac8-452836ea9681'}

The following is a log where the handler was not triggered

YQiFEOQc1cHhuPLSAAAC: Sending packet OPEN data {'sid': 'YQiFEOQc1cHhuPLSAAAC', 'upgrades': [], 'pingTimeout': 20000, 'pingInterval': 25000}
YQiFEOQc1cHhuPLSAAAC: Received request to upgrade to websocket
YQiFEOQc1cHhuPLSAAAC: Upgrade to websocket successful
YQiFEOQc1cHhuPLSAAAC: Received packet MESSAGE data 0/terminal,{"Authorization":"Bearer xxxxxxx"}
YQiFEOQc1cHhuPLSAAAC: Sending packet MESSAGE data 0/terminal,{"sid":"ROpPs___EGVGm32uAAAD"}
YQiFEOQc1cHhuPLSAAAC: Received packet MESSAGE data 2/terminal,["shell",{"action":"start","cid":"3940d07c61dc","pid":"1721288606588"}]
YQiFEOQc1cHhuPLSAAAC: Received packet MESSAGE data 2/terminal,["resize",{"pid":"1721288606588","msg":{"rows":22,"cols":75}}]
YQiFEOQc1cHhuPLSAAAC: Received packet MESSAGE data 2/terminal,["shell",{"action":"stop","pid":"1721288606588"}]

[miguelgrinberg]

Try registering the namespace before you initialize the extension. If that does not help, then please create a runnable version of your application demonstrating the problem so that I can debug this further.

[lylanfree]

Here is basic information of my application

➜  python -V
Python 3.10.12
 ➜  pip freeze | grep Flask
Flask==3.0.3
Flask-Cors==4.0.1
Flask-JWT-Extended==4.6.0
Flask-SocketIO==5.3.6
Flask-SQLAlchemy==3.1.1

buggy-code

I might find why it happens, below is the version of the code with the bug

# app.py
def create_app(config_name = None):
    app = Flask('MYAPP')

    app.config.from_object(config[config_name])
    app.static_folder = app.config['STATIC_FOLDER']
    app.static_url_path = app.config['STATIC_URL_PATH']

    register_extensions(app)

    return app

def register_socketio(app):
    socketio.on_namespace(TerminalNamespace('/terminal'))
    if app.config["CORS_ENABLE"]:
        socketio.init_app(app, cors_allowed_origins=app.config['CROSS_ORIGIN'], engineio_logger = app.config['DEBUG'])
    else:
        socketio.init_app(app, engineio_logger = app.config['DEBUG'])

def register_extensions(app):
    db.init_app(app)
    jwt.init_app(app)
    if app.config["CORS_ENABLE"]:
        CORS(app, resources={r"/*": {"origins": app.config['CROSS_ORIGIN']}})
    register_socketio(app)

flask_app = create_app()

if __name__ == '__main__': 
    socketio.run(flask_app, host = flask_app.config['HOST'], port = flask_app.config['PORT'], debug = flask_app.config['DEBUG'])

when I run code above, the output of cmd is as below, client connects to server and send message but not trigger handle

Server initialized for eventlet.
 * Restarting with stat
Server initialized for eventlet.
 * Debugger is active!
 * Debugger PIN: 244-574-081
(1432961) wsgi starting up on http://192.168.31.14:5000
BU1HuN3QJFuUOjxXAAAA: Sending packet OPEN data {'sid': 'BU1HuN3QJFuUOjxXAAAA', 'upgrades': ['websocket'], 'pingTimeout': 20000, 'pingInterval': 25000}
BU1HuN3QJFuUOjxXAAAA: Received packet MESSAGE data 0/socket.io,{"Authorization":"Bearer xxxxx"}
BU1HuN3QJFuUOjxXAAAA: Sending packet MESSAGE data 0/socket.io,{"sid":"KEsW0AdJ9x6i686IAAAB"}
BU1HuN3QJFuUOjxXAAAA: Received request to upgrade to websocket
BU1HuN3QJFuUOjxXAAAA: Upgrade to websocket successful
BU1HuN3QJFuUOjxXAAAA: Received packet MESSAGE data 2/socket.io,["shell",{"action":"start","cid":"e7527b69597e","pid":"e7527b69597e"}]
BU1HuN3QJFuUOjxXAAAA: Received packet MESSAGE data 2/socket.io,["resize",{"pid":"e7527b69597e","msg":{"rows":22,"cols":75}}]
BU1HuN3QJFuUOjxXAAAA: Sending packet PING data None
BU1HuN3QJFuUOjxXAAAA: Received packet PONG data 
BU1HuN3QJFuUOjxXAAAA: Received packet MESSAGE data 2/socket.io,["shell",{"action":"stop","pid":"e7527b69597e"}]

normal code

After adjusting the order of the codes as below, The handle can be triggered normally, and the output is as follows

def register_extensions(app):
    db.init_app(app)
    jwt.init_app(app)
    if app.config["CORS_ENABLE"]:
        CORS(app, resources={r"/*": {"origins": app.config['CROSS_ORIGIN']}})

if __name__ == '__main__': 
    register_socketio(app)
    socketio.run(flask_app, host = flask_app.config['HOST'], port = flask_app.config['PORT'], debug = flask_app.config['DEBUG'])

FINuDC44d23jXiPBAAAA: Sending packet OPEN data {'sid': 'FINuDC44d23jXiPBAAAA', 'upgrades': ['websocket'], 'pingTimeout': 20000, 'pingInterval': 25000}
FINuDC44d23jXiPBAAAA: Received packet MESSAGE data 0/socket.io,{"Authorization":"Bearer xxxxx"}
FINuDC44d23jXiPBAAAA: Sending packet MESSAGE data 0/socket.io,{"sid":"0S4--749klZPj3X8AAAB"}
FINuDC44d23jXiPBAAAA: Received request to upgrade to websocket
FINuDC44d23jXiPBAAAA: Upgrade to websocket successful
FINuDC44d23jXiPBAAAA: Received packet MESSAGE data 2/socket.io,["shell",{"action":"start","cid":"da4945135f36","pid":"da4945135f36"}]
DEBUG in socket: /socket.io-0S4--749klZPj3X8AAAB-on shell:{'action': 'start', 'cid': 'da4945135f36', 'pid': 'da4945135f36'}
FINuDC44d23jXiPBAAAA: Sending packet MESSAGE data 2/socket.io,["message",{"pid":"da4945135f36","msg":"Connection established\r\n","new_id":"e88e9f60-f8b8-40ca-a7f6-ef53b674992b"}]
FINuDC44d23jXiPBAAAA: Received packet MESSAGE data 2/socket.io,["resize",{"pid":"da4945135f36","msg":{"rows":22,"cols":75}}]
FINuDC44d23jXiPBAAAA: Sending packet MESSAGE data 2/socket.io,["message",{"pid":"e88e9f60-f8b8-40ca-a7f6-ef53b674992b","msg":"root@da4945135f36:/# "}]
FINuDC44d23jXiPBAAAA: Received packet MESSAGE data 2/socket.io,["shell",{"action":"stop","pid":"e88e9f60-f8b8-40ca-a7f6-ef53b674992b"}]
DEBUG in socket: /socket.io-0S4--749klZPj3X8AAAB-on shell:{'action': 'stop', 'pid': 'e88e9f60-f8b8-40ca-a7f6-ef53b674992b'}

But why is this happening !!!

[miguelgrinberg]

I can't really tell from snippets. This is likely a bug in your application. If you prepare a complete and runnable example that I can debug I'll be able to tell you what's going on.