app.py

#!/usr/bin/env python3
#
# Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
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# Software is furnished to do so, subject to the following conditions:
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import os
import dash
import http
import pprint
import traceback

import warnings  # supress dash_auth import warnings
warnings.filterwarnings("ignore", category=UserWarning)
import dash_auth

from dash import dcc, Input, Output
from dash.exceptions import PreventUpdate

from config import config, print_config
from server import Server

from layout import create_grid, create_navbar, create_alerts, create_stream_dialog, create_model_dialog, create_actions_dialog


# create the dash app
external_scripts = ['https://webrtc.github.io/adapter/adapter-latest.js']
external_stylesheets = ['https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css'] # 'https://use.fontawesome.com/releases/v5.8.1/css/all.css'

app = dash.Dash(__name__, 
                title=config['dash']['title'],
                update_title=None,
                external_scripts=external_scripts, 
                external_stylesheets=external_stylesheets, 
                suppress_callback_exceptions=True)
                
webserver = app.server

if len(config['dash']['users']) > 0:
    auth = dash_auth.BasicAuth(app, config['dash']['users'])


# define the default layout
app.layout = dash.html.Div([
    create_navbar(),
    create_grid(),
    create_alerts(),
    create_stream_dialog(),
    create_model_dialog(),
    create_actions_dialog(),
    dcc.Store(id='server_resources'),
    dcc.Interval(id='server_refresh_timer', interval=config['dash']['refresh'])
], className='dbc')


@app.callback(Output('server_resources', 'data'),
              Input('server_refresh_timer', 'n_intervals'),
              Input('server_resources', 'data'))
def on_refresh(n_intervals, previous_resources):
    """
    Get the latest resources config from the server.
    This can trigger updates to the clientside nav structure.
    """
    try:
        server_resources = Server.request('/resources').json()
    except Exception as error:
        traceback.print_exc()
        print(f"[dash]   error refreshing server resources")
        raise PreventUpdate

    if previous_resources is not None:
        if server_resources == previous_resources:
            raise PreventUpdate   # if the config hasn't changed, skip the update

    print(f"[dash]   received updated resources config from backend server:")
    pprint.pprint(server_resources, indent=4)
    return server_resources


if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser(epilog="see config.py or data/config.json for more settings")
    
    parser.add_argument("--host", default=None, type=str, help="interface for the webserver to use (default is all interfaces, 0.0.0.0)")
    parser.add_argument("--port", default=None, type=int, help="port used for webserver (default is 8050)")
    parser.add_argument("--ssl-key", default=os.getenv('SSL_KEY'), type=str, help="path to PEM-encoded SSL/TLS key file for enabling HTTPS")
    parser.add_argument("--ssl-cert", default=os.getenv('SSL_CERT'), type=str, help="path to PEM-encoded SSL/TLS certificate file for enabling HTTPS")
    parser.add_argument("--resources", default=None, type=str, help="path to JSON config file to load initial server resources from")
    
    args = parser.parse_args()

    if args.host:
        config['dash']['host'] = args.host
        
    if args.port:
        config['dash']['port'] = args.port

    if args.ssl_key:
        config['server']['ssl_key'] = args.ssl_key
        
    if args.ssl_cert:
        config['server']['ssl_cert'] = args.ssl_cert
        
    if args.resources:
        config['server']['resources'] = args.resources
        
    print_config(config)
    
    # check if HTTPS/SSL requested
    ssl_context = None
    
    if config['server']['ssl_cert'] and config['server']['ssl_key']:
        ssl_context = (config['server']['ssl_cert'], config['server']['ssl_key'])
        print(ssl_context)
        
    # start the backend server
    Server(**config['server']).start()

    # disable code reloading because it starts the app multiple times (https://dash.plotly.com/devtools)
    # https://community.plotly.com/t/dash-multi-page-app-functions-are-called-twice-unintentionally/46450
    app.run_server(host=config['dash']['host'], port=config['dash']['port'], ssl_context=ssl_context, debug=True, use_reloader=False)

else:
    # gunicorn instance
    # start/connect to the backend server
    Server(**config['server']).connect()