dash-celery-app.py

from celery import Celery
import copy
import dash
from dash.dependencies import Input, Output
import dash_html_components as html
import dash_core_components as dcc
import datetime
from flask_caching import Cache
import numpy as np
import os
import pandas as pd
import time


app = dash.Dash(__name__)



def make_celery(server):
    celery = Celery(app.import_name,
                    backend=server.config['CELERY_RESULT_BACKEND'],
                    broker=server.config['CELERY_BROKER_URL'])
    celery.conf.update(server.config)
    TaskBase = celery.Task
    class ContextTask(TaskBase):
        abstract = True
        def __call__(self, *args, **kwargs):
            with server.app_context():
                return TaskBase.__call__(self, *args, **kwargs)
    celery.Task = ContextTask
    return celery


app.server.config.update(
    CELERY_BROKER_URL='redis://localhost:6379',
    CELERY_RESULT_BACKEND='redis://localhost:6379',
)
celery = make_celery(app.server)

df = pd.DataFrame({
    'category': (
        (['apples'] * 5) +
        (['oranges'] * 10) +
        (['figs'] * 20) +
        (['pineapples'] * 15)
    )
})
df['x'] = np.random.randn(len(df['category']))
df['y'] = np.random.randn(len(df['category']))

app.layout = html.Div([
    dcc.Dropdown(
        id='dropdown',
        options=[{'label': i, 'value': i} for i in df['category'].unique()],
        value='apples'
    ),
    html.Div([
        html.Div(dcc.Graph(id='graph-1'), className="six columns"),
        html.Div(dcc.Graph(id='graph-2'), className="six columns"),
    ], className="row"),
    html.Div([
        html.Div(dcc.Graph(id='graph-3'), className="six columns"),
        html.Div(dcc.Graph(id='graph-4'), className="six columns"),
    ], className="row")
])


@cache.memoize()
@celery.task()
def global_store(value):
    # simulate expensive query
    print('Computing value with {}'.format(value))
    time.sleep(5)
    return df[df['category'] == value]


def generate_figure(value, figure):
    fig = copy.deepcopy(figure)
    filtered_dataframe = global_store(value)
    fig['data'][0]['x'] = filtered_dataframe['x']
    fig['data'][0]['y'] = filtered_dataframe['y']
    fig['layout'] = {'margin': {'l': 20, 'r': 10, 'b': 20, 't': 10}}
    return fig


@app.callback(Output('graph-1', 'figure'), [Input('dropdown', 'value')])
def update_graph_1(value):
    return generate_figure(value, {
        'data': [{
            'type': 'scatter',
            'mode': 'markers'
        }]
    })


@app.callback(Output('graph-2', 'figure'), [Input('dropdown', 'value')])
def update_graph_2(value):
    return generate_figure(value, {
        'data': [{
            'type': 'scatter',
            'mode': 'lines',
            'line': {'shape': 'spline'}
        }]
    })


@app.callback(Output('graph-3', 'figure'), [Input('dropdown', 'value')])
def update_graph_3(value):
    return generate_figure(value, {
        'data': [{
            'type': 'bar',
        }]
    })


@app.callback(Output('graph-4', 'figure'), [Input('dropdown', 'value')])
def update_graph_4(value):
    return generate_figure(value, {
        'data': [{
            'type': 'histogram2dcontour',
        }]
    })


# Dash CSS
app.css.append_css({
    "external_url": "https://codepen.io/chriddyp/pen/bWLwgP.css"})
# Loading screen CSS
app.css.append_css({
    "external_url": "https://codepen.io/chriddyp/pen/brPBPO.css"})

if __name__ == '__main__':
    app.run_server(debug=True, processes=6)