What is the proper way to disconnect a client from the server side?

Greetings, I am trying to disconnect a client from the server side. I use aiohttp with socketio.

I use:

class GlobalNamespaceServer(AsyncNamespace):
    # namespace for /
    async def on_disconnect(self, sid: str):
        await self.emit('disconnect', room=sid)

    async def on_connect(self, sid, environ):
        # I need to send event 'accessDenied'
        await self.emit('accessDenied', 'smth', room=sid)
        loop.create_task(self.disconnect(sid))
        return True

As far as I know, the problem is here:

            ret = await s.handle_get_request(environ)
            if s.closed:
                # websocket connection ended, so we are done (socket has already been deleted by `sio.disconnect()`)
                del self.sockets[sid]
            return ret

in _handle_connect function.

Logs

2019-10-23 17:46:33,558 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Sending packet OPEN data {'sid': 'e6c6d024dd41435084460bd42ffc93bb', 'upgrades': [], 'pingTimeout': 60000, 'pingInterval': 25000}
2019-10-23 17:46:33,559 [INFO] socketio.server: emitting event "accessDenied" to e6c6d024dd41435084460bd42ffc93bb [/]
2019-10-23 17:46:33,560 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Sending packet MESSAGE data 2["accessDenied",{"data":{"code":"notAuthorized","description":"text"},"headers":{}}]
2019-10-23 17:46:33,561 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Sending packet MESSAGE data 0
2019-10-23 17:46:33,561 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Received request to upgrade to websocket
2019-10-23 17:46:33,562 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Upgrade to websocket successful
2019-10-23 17:46:38,564 [INFO] socketio.server: emitting event "disconnect" to e6c6d024dd41435084460bd42ffc93bb [/]
2019-10-23 17:46:38,565 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Sending packet MESSAGE data 2["disconnect",null]
2019-10-23 17:46:38,565 [INFO] socketio.server: Disconnecting e6c6d024dd41435084460bd42ffc93bb [/]
2019-10-23 17:46:38,565 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Sending packet MESSAGE data 1
2019-10-23 17:46:38,565 [INFO] engineio.server: e6c6d024dd41435084460bd42ffc93bb: Sending packet CLOSE data None
2019-10-23 17:46:38,569 [ERROR] aiohttp.server: Error handling request
Traceback (most recent call last):
  File ".../lib/python3.7/site-packages/aiohttp/web_protocol.py", line 418, in start
    resp = await task
  File "...lib/python3.7/site-packages/aiohttp/web_app.py", line 458, in _handle
    resp = await handler(request)
  File "...lib/python3.7/site-packages/aiohttp/web_middlewares.py", line 119, in impl
    return await handler(request)
  File "...lib/python3.7/site-packages/aiohttp/web_middlewares.py", line 109, in impl
    return await handler(request)
  File "...lib/python3.7/site-packages/engineio/asyncio_server.py", line 234, in handle_request
    b64, jsonp_index)
  File "...lib/python3.7/site-packages/engineio/asyncio_server.py", line 388, in _handle_connect
    del self.sockets[sid]
KeyError: 'e6c6d024dd41435084460bd42ffc93bb'

Could you please give me advice, what is the proper way?

[miguelgrinberg]

It appears this issue is the same as the one reported in miguelgrinberg/python-engineio#179, which is now fixed.

[dskorykh]

Hello! I have the same problem but with socketio.Server (using eventlet as async_mode). I found this happening after upgrading python-socketio to v4.3.1 and I get an error what occurs when I call disconnect from the server side, it’s not persistent (exception is raised approx one time out of ten). It can be related to doing some stuff in the disconnect handler (cleaning hooks bound to client take a little time), but earlier I didn’t see this behavior.

I saw this PR https://github.com/miguelgrinberg/python-engineio/pull/146, and what do you think about adding the same logic to the engineio/server.py?

Error trace:

127.0.0.1 - - [13/Nov/2019 20:05:43] "POST /socket.io/?EIO=3&transport=polling&t=Mvbkc3Z&sid=6152cec661024233ad1108683dfea2ab HTTP/1.1" 200 219 0.000988
127.0.0.1 - - [13/Nov/2019 20:05:43] "GET /socket.io/?EIO=3&transport=polling&t=Mvbkc3a&sid=6152cec661024233ad1108683dfea2ab HTTP/1.1" 200 183 0.054349
reboot called
disconnect hooks
disconnect hooks ended
127.0.0.1 - - [13/Nov/2019 20:05:44] "GET /socket.io/?EIO=3&transport=websocket&sid=6152cec661024233ad1108683dfea2ab HTTP/1.1" 200 0 0.789681
Exception in thread Thread-26:
Traceback (most recent call last):
  File "../lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "../lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "../lib/python2.7/dist-packages/socketio/server.py", line 648, in _handle_event_internal
    r = server._trigger_event(data[0], namespace, sid, *data[1:])
  File "../lib/python2.7/dist-packages/socketio/server.py", line 677, in _trigger_event
    return self.handlers[namespace][event](*args)
  File "../lib/python2.7/dist-packages/flask_socketio/__init__.py", line 284, in _handler
    *args)
  File "../lib/python2.7/dist-packages/flask_socketio/__init__.py", line 698, in _handle_event
    ret = handler(*args)
  File "/home/dmitry/projects/Flask-SocketIO/test_disconnect/app_test.py", line 37, in reboot
    disconnect()
  File "../lib/python2.7/dist-packages/flask_socketio/__init__.py", line 922, in disconnect
    return socketio.server.disconnect(sid, namespace=namespace)
  File "../lib/python2.7/dist-packages/socketio/server.py", line 508, in disconnect
    self.eio.disconnect(sid)
  File "../lib/python2.7/dist-packages/engineio/server.py", line 292, in disconnect
    del self.sockets[sid]
KeyError: '6152cec661024233ad1108683dfea2ab'

Simplified server-side code

#!/usr/bin/env python
import eventlet
eventlet.monkey_patch()

from flask import Flask, render_template
from flask_socketio import SocketIO, disconnect


async_mode = 'eventlet'

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
socketio = SocketIO(app, async_mode=async_mode)


def do_some_stuff(): # if there is a some cpu-bound hook, chance of failure increases (just to reproduce)
    a = 0
    for i in range(10000000):
        a += i


@app.route('/')
def index():
    return render_template('index.html', async_mode=socketio.async_mode)


@socketio.on('disconnect')
def disconnect_handler():
    print("run disconnect hooks")
    do_some_stuff()
    print("disconnect hooks done")


@socketio.on('reboot')
def reboot():
    print("reboot called")
    disconnect()
    # reboot 


if __name__ == '__main__':
    socketio.run(app, host="0.0.0.0", port=2000, debug=True)