KeyError raised in handle_javascript_response method of Client

[ruiheng]

Description

This kind of exception as shown in the following logs, pops up from time to time in the logs of my app.

Task exception was never retrieved
future: <Task finished name='Task-1926' coro=<AsyncServer._handle_event_internal() done, defined at /home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/socketio/async_server.py:608> exception=KeyError('f4d16bd7-1174-443c-b90d-e46b099e27b5')>
Traceback (most recent call last):
  File "/home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/socketio/async_server.py", line 610, in _handle_event_internal
    r = await server._trigger_event(data[0], namespace, sid, *data[1:])
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/socketio/async_server.py", line 641, in _trigger_event
    ret = handler(*args)
          ^^^^^^^^^^^^^^
  File "/home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/nicegui/nicegui.py", line 203, in _on_javascript_response
    client.handle_javascript_response(msg)
  File "/home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/nicegui/client.py", line 269, in handle_javascript_response
    JavaScriptRequest.resolve(msg['request_id'], msg.get('result'))
  File "/home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/nicegui/javascript_request.py", line 20, in resolve
    request = cls._instances[request_id]
              ~~~~~~~~~~~~~~^^^^^^^^^^^^
KeyError: 'f4d16bd7-1174-443c-b90d-e46b099e27b5'

I don't know how to reproduce this issue. However theses errors usually occur on "slow" or complicate pages.

My guess is: after "await js_request" throws TimeoutError, the JavaScriptRequest instance gets deleted from JavaScriptRequest._instances dict. Subsequently, when the response of this JavaScriptRequest arrives, a KeyError is raised.

Alternatively there might be some requirements for using 'ui.run_javascript' that I am not aware of.

[rodja]

I don't know how to reproduce this issue. However theses errors usually occur on "slow" or complicate pages.

Are you using async/await properly? See https://github.com/zauberzeug/nicegui/wiki/FAQs#why-is-my-long-running-function-blocking-ui-updates

[ruiheng]

Thanks. I did not know the 'loop.set_debug' method.

After I add these code

def startup():
    loop = asyncio.get_running_loop()
    loop.set_debug(True)
    loop.slow_callback_duration = 0.05

app.on_startup(startup)

I have this new warning in logs:

Executing <Task pending name='....' coro=<run_coro_on_ui_loop.<locals>.wrapped() running at /.../utils.py:994> wait_for=<Future pending cb=[Protocol._on_waiter_completed(), Task.task_wakeup()] created at /home/ruiheng/.cache/pypoetry/virtualenvs/lyceum-NKmSERnC-py3.11/lib/python3.11/site-packages/asyncpg/connection.py:350> created at /home/ruiheng/lyceum/lyceum/page/utils.py:1001> took 0.415 seconds

It seems that something related to asyncpg takes a little longer time to run. I don't know if 0.4 sec is a big issue. Anyway, the KeyError exception still occurs.

I forgot to mention that my browser that I use to test, actually have some performance issues. I can notice poor performance on all web pages.

[falkoschindler]

@ruiheng Calling a function repeatedly that takes 0.4 sec can sum up and cause problems.

Can you, please, try to provide a minimum reproducible example? Or should we close this issue?