KeyError in ui.log after client disconnected
#3028
Comments
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Hi @Thermaltech, thanks for reaching out! I'm struggling to reproduce the error. Your code is missing some imports like import logging
from time import localtime, strftime
from nicegui import ui
class LogElementHandler(logging.Handler):
def __init__(self, element: ui.log, level: int = logging.NOTSET) -> None:
self.element = element
super().__init__(level)
def emit(self, record: logging.LogRecord) -> None:
try:
msg = f'{strftime("%A, %B %d, %Y, %H:%M:%S", localtime(record.created))} - {record.levelname} - {record.name} - {record.message}'
self.element.push(msg)
except Exception:
self.handleError(record)
@ui.page('/')
def page():
ui_logger = logging.getLogger('wm')
log = ui.log(max_lines=10)
ui_logger.addHandler(LogElementHandler(log))
ui.button('Clear', on_click=log.clear)But I don't get any exception when closing the page. Maybe because there is no log happening? |
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Falko, Thanks for the quick reply. The ui_header and ui_footer didn't have anything to do with the problem at hand, so I didn't include them. Sorry if it caused any confusion. The logging events are happening all over the program in different modules, and are being monitored / displayed by this page by attaching to the global logger "wm" by name. So the LogElementHandler would still be registered with in the logging module, and would still be firing events... Honestly, what I think is happening is due to my software not being aware that the page is gone, and the logging handler is still trying to send / delete data for the nicegui logging element by way of the LogElementHandler, what I may have to do is add and remove the handler based on client connect disconnect, or just push a copy of the log file on demand. In short, I may be misguided in my thoughts as to how the nicegui log implementation is intended to be used. I am quite sure if all the logging is happening on the page that is pushing the data to the same page, all would be OK. This would mean that when the page is closed, the events inherently stop. Since the logging events are happening elsewhere within my program, and the logging handler is attempting to push / remove data from a now non-existent element, is where the problem lies.... What has me a little confused is that the logging events being pushed to a non-existent logging element does not cause an error, but when the following code executes to remove old items from the log element, all hell breaks loose... while self.max_lines is not None and len(self.default_slot.children) > self.max_lines:
self.remove(0)Is there some simple method that could be used to determine when the page is closed so that I can automatically remove the LogElementHandler instance? Cheers. |
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Just a FYI. Problem solved by addming client connect / disconnect handlers to automatically add and remove the LogElemenHandler to the logger. The nicegui Client class made this really easy. Thanks for making a great library! Revised code: import logging
from time import strftime, localtime
from nicegui import ui, Tailwind, Client
import modules.tts_config_loader as cfg
import ui_header
import ui_footer
logger = logging.getLogger('wm.ui.event_log')
class LogElementHandler(logging.Handler):
"""A logging handler that emits messages to a log element."""
def __init__(self, element: ui.log, level: int = logging.NOTSET) -> None:
self.element = element
super().__init__(level)
def emit(self, record: logging.LogRecord) -> None:
try:
msg = f'{strftime("%A, %B %d, %Y, %H:%M:%S", localtime(record.created))} - {record.levelname} - {record.name} - {record.message}'
self.element.push(msg)
except Exception:
self.handleError(record)
'''
UI - EVENT_LOG
'''
@ui.page('/event_log')
def content(client: Client):
wm_config = cfg.configs['wm'].config
def connected():
# Add log event handler
logging.getLogger('wm').addHandler(log_handler)
def disconnected():
# Remove log event handler
logging.getLogger('wm').removeHandler(log_handler)
def clear_log():
logger.debug(f'Client cleared local event log with id: {client.id}')
log_element.clear()
client.on_connect(connected)
client.on_disconnect(disconnected)
# Page Configuration
ui.page_title(f"{wm_config['SETTINGS']['TITLE']} - Event Log")
ui_header.content()
ui_footer.content()
with ui.card().classes('w-full'):
# Title
lbl_log = ui.label('Event Log')
lbl_log.tailwind('font-bold')
# Log viewer
log_element = ui.log(max_lines = 50)
log_element.tailwind('h-[500px]')
log_handler : LogElementHandler = LogElementHandler(log_element)
# Clear log button
ui.button('CLEAR EVENT LOG', on_click=lambda : clear_log()) |
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Thanks for the clarification, @Thermaltech! Just recently we ran into a similar problem. Let me explain: When you register some UI code (like adding a line of text to Since a memory leak can be pretty critical and it happens so easily, we should implement some safety net. We already experimented with detecting access to any client attribute after it disconnected, but this felt like a bit too strict. Something similar would be a useful feature though. |
falkoschindler
changed the title
ui.log after client disconnected
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@falkoschindler I saw this log on our https://nicegui.io website: |
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There is some other kind of log entries appearing which may be related: This seems to also make the server unstable (eg. not responding to health checks). I still don't know the real cause... |
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@rodja This clearly points to our "Attach to a logger" demo, which is exactly what we created this warning for. |
Description
Hey!
Not sure if this is a bug, or an issue with my code (see below), but it seems that when the ui.log element is used with the python logging module, the page / element throws an error under the following conditions:
If I set max_lines to None (default), then no error occurs. as this seems to be related to the nicegui codebase in log.py, line 28/29 where the LogeElementhandler in my code is attempting to log an event / trim the list, but nicegui has already cleaned up and deleted the log element, hence the error.
The Error:
My Code:
In any case, thanks so much for any help that can be provided. Cheers!
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