Dash Long Callbacks Not Working

kev · February 11

Hi all,

I'm struggling to get long callbacks to work in Dataiku. When I initalize the app = dash.Dash() instance, the application does not run at all. When I remove it, the application runs but the callback does not work at all. Currently, it only works with a regular callback but I need it to work with a long callback. Thanks in advance!

Best,

import time

import dash

from dash import html, Input, Output, callback

from dash.long_callback import DiskcacheLongCallbackManager

# import dataiku


## Diskcache

import diskcache

import logging


### python-lib function

from long_callback_function import long_callback_function


# logger = logging.getLogger(__name__)



cache = diskcache.Cache("./cache")

long_callback_manager = DiskcacheLongCallbackManager(cache)

app = dash.Dash(__name__, long_callback_manager=long_callback_manager)





app.layout = html.Div(

    [

        html.Div([html.P(id="paragraph_id", children=["Button not clicked"])]),

        html.Button(id="button_id", children="Run Job!"),

        html.Button(id="cancel_button_id",children="Cancel Running Job")

    ]

)



@app.long_callback(

    Output("paragraph_id", "children"),

    Input("button_id", "n_clicks"),

    manager=long_callback_manager,

    running = [

        (Output("button_id","disabled"),True,False),

        (Output("cancel_button_id","disabled"),False,True),

    ],

    cancel=[Input("cancel_button_id","n_clicks")],

)

def long_callback(n_clicks):


    return long_callback_function(n_clicks)

######################### Long callback function
import time


def long_callback_function(n_clicks):

    time.sleep(10)

    return [f"Clicked {n_clicks} times PLEASE"]

Sarina · February 19

Hi @kev,

Thank you for your question about using long callbacks within a dash app! You'll want to use the following structure utilizing project libraries to define your long callbacks.

So in your webapp, you'll define your diskcache like so:

import diskcache
cache = diskcache.Cache(".")
long_callback_manager = DiskcacheLongCallbackManager(cache)

Now, in your project library you'll define your callback code instead of in your webapp code (as Python self-inspection capabilities require the code to be in a full-fledged file) like so:

attachment?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6MTE1Mzc2ODc0OSwiZG9tYWluIjoiZGF0YWlrdS5mcmVzaGRlc2suY29tIiwiYWNjb3VudF9pZCI6MTEyOTc5fQ.ojo5g6ZIM0NaZOsdJ8Tb1PQbexm3XDV6LmeixICk_yo

Then, in your webapp you can call the project library callback code. Here's a full example.

[webapp code]

import time
import dash
from dash import html, Input, Output
from dash.long_callback import DiskcacheLongCallbackManager
from my_dash.callbacks import define_callback

import diskcache
cache = diskcache.Cache(".")
long_callback_manager = DiskcacheLongCallbackManager(cache)

app.layout = html.Div(
[
html.Div([html.P(id="paragraph_id", children=["Button not clicked"])]),
html.Button(id="button_id", children="Run Job!"),
]
)

define_callback(app, long_callback_manager)

Project library code stored in a folder named my_dash and a file named callbacks.py [project library (lib > python > my_dash > callbacks.py)]

import time
import dash
from dash import Input, Output

def define_callback(app, long_callback_manager):
@app.long_callback(
output=Output("paragraph_id", "children"),
inputs=Input("button_id", "n_clicks"),
manager=long_callback_manager,
)
def callback(n_clicks):
time.sleep(20)
return [f"Clicked {n_clicks} times"]

I hope that's helpful!

Thank you,
Sarina

kev · February 20

It works, thank you Sarina!

Dash Long Callbacks Not Working

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