Python Websockets Handle login errors elegantly

w.murray

Hi,

I am trying to make the samples more production ready by handling error conditions. Testing an incorrect password, I am receiving the following text:

ERROR:root:LOGIN STATUS: {

"Domain":"Login",

"ID":1,

"Key":{

"Name":"rateserverss"

},

"State":{

"Code":"UserUnknownToPermSys",

"Data":"Suspect",

"Stream":"Closed",

"Text":"rateserverss, unknown to system."

},

"Type":"Status"

}

I am detecting this, however how do I terminate the loop in the main program?

logger.error("LOGIN STATUS: %s", json.dumps(message_json, sort_keys=True, indent=2, separators=(',', ':')))
if message_json['State']['Stream'] != "Open" or message_json['State']['Data'] != "Ok":
    logger.error("Login Request rejected / failed:"+message_json['State']['Text'])
    shutdown_app = True
    exit(5000)

The routine exits, however the main code is never executed and the program just hangs, processing additional callbacks.

Note I am using threading and the run_forever version of the web socket app:

ws_address = "ws://{}:{}/WebSocket".format(host, port)
print("Connecting to WebSocket " + ws_address + " ...")
logger.info("Connecting to WebSocket " + ws_address + " ...")
web_socket_app = websocket.WebSocketApp(ws_address, header=['User-Agent: Python'],
                                        on_message=on_message,
                                        on_error=on_error,
                                        on_close=on_close,
                                        subprotocols=['tr_json2'])
web_socket_app.on_open = on_open

# Event loop
wst = threading.Thread(target=web_socket_app.run_forever)

Jirapongse

@w.murray

I found a solution on StackOverflow.

In the callback method, you can call the ws.close() method to close the websocket connection.

    if message_type == "Status" and message_json['State']['Stream']=="Closed" and message_json['Domain']=="Login":
        print("Login Closed")
        ws.close()

In the main thread, you can call wst.is_alive() method to check whether a thread is alive.

    try:
        while True:
            time.sleep(1)
            if wst.is_alive() == False:
                exit(0)

w.murray

Note that the code works perfectly with correct login credentials

w.murray

The problem was not in the callback...it was in the main routine where there was a loop waiting for a successful login.

My code:

while not logged_in:
time.sleep(1)

This would lead to an endless loop when login fails.

Sample code on github:

while not logged_in and (not shutdown_app):
    time.sleep(1)

shutdown_app also needs to be set in the callback routine:

else:
    logger.error("LOGIN STATUS: %s", json.dumps(message_json, sort_keys=True, indent=2, separators=(',', ':')))
    if message_json['State']['Stream'] != "Open" or message_json['State']['Data'] != "Ok":
        logger.error("Login Request rejected / failed:"+message_json['State']['Text'])
shutdown_app = True

w.murray

Thanks for the response - turns out the callback was working OK and the problem was actually in the main code - see my posted response for details