Data stopping the callback to be triggered correctly when used with State( Datatable, 'data')?

Dash Python
,
1

So, I am looking for an explanation of a curious behavior.

I reduced it as much as i could. On my dashboard page i got two buttons and a dash datatable. Button 1 loads data from a file displaying it in the datatable. Button 2 triggers a computation with the data selected. Button 2 will be the problem later. The callback definition for button 2 looks like this:

@app.callback(
Output('outgoing-warnings','children'),
Input('simulation-order-button', 'n_clicks'),
State('datatable-simulation-order', 'selected_rows'),
State('datatable-simulation-order', 'data'),
prevent_initial_call = True
)
def callback_find_needed_cassettes(n, rows, orders):
    print(n)
    return 'test'

The following problem occured: When clicking button 2 the callback is not “triggered” correctly meaning that the code defined in the function is not triggered. However, the name/title of the chrome window changes to updating… One problem is that it kinda wasnt a 100% occurence problem. In my feeling it worked like only in 0.01% of the cases with many data but 80% of the times with small data until it stopped completely.

So the callback itself basically does nothing anymore. It is working when i do not load any data with button 1 into the datatable. When data is loaded it does not work anymore. This behavior started randomly yesterday and i was looking for a fix desperately. It does work when the last state is commented out. Thats why i completely make the state/data responsible for the problem. (The data did not change in last couple of months at all.)

As it seems i got it fixed now by changing the port of my app (i am confused by this). While writing this post i asked a colleague of mine to clone my repo and try it. Just to be sure. It worked. I was curious. Different browser didnt work on my pc but when i changed the port of my app it started working again.

Is someone out there that got any idea? Without a minimal example it will be rather hard too but did not had the time yet to write/test one. I dont even know if i would be able to find one as this dashboard also worked fine for like ~9 months and started to get problems this week.

Thanks in advance

EDIT: Changing my port only worked briefly. I restarted my pc againg and noticed something in my VS Code. As i work remote per ssh on our developing machine the ports need to be forwarded. They were shifted by one in my vs code. I dont know why. So 3000 was mapped to my local 3001. I changed that, no idea if this or the restart helped but at the moment its running a little bit longer than before.

2

Hey @korzi, do you run the app with debug=True? Do you get any errors?

3

Also, do any errors show in your browser developer tools window, in the console or network tabs?

4

App is run with debug=True but no errors occur. I see in vs code that nothing happens. The print is not displayed. The only thing i see that the chrome tab header changes to updating… on button click.

5

I had a look insight but i saw nothing that catched my attention or sounded like a problem.