Running Apps using JupyterLab Proxy AND as App not working since 'port in use'

Environment

This should work on Domino 4 and Domino 5 Environments. Tested on Domino 5.

Issue

The example code for Dash works as an App but when I try to use it inside a Workspace, it doesn't work!

Can you help me run App inside a Workspace? This does not work smoothly.

Can we combine the code for Apps to work both as App and inside a Workspace?

Resolution

Since the URL for Apps and JupyterLab Proxy is slightly different, and the port 8888 is already used by a Workspace, the code would need to be constantly changed between testing and deployment OR you'll use the environment or try: commands in Python.

One code which would work if you use JupyterLab:

from dash import Dash, dash_table
import pandas as pd
import os

# Configure Dash to recognize the URL of the container
user = os.environ.get("DOMINO_PROJECT_OWNER")
project = os.environ.get("DOMINO_PROJECT_NAME")
runid = os.environ.get("DOMINO_RUN_ID")
jupyter = os.environ.get("JUPYTER_SERVER_ROOT")

# If this variable exists, we're running a Workspace
if jupyter == '/':
    debug=False
    port=8889
    runurl = '/' + user + '/' + project + '/notebookSession/' + runid + '/proxy/8889/'
else:
    debug=True
    port=8888
    runurl = '/' + user + '/' + project + '/r/notebookSession/' + runid + '/'

df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/solar.csv')

app = Dash(__name__, routes_pathname_prefix='/', requests_pathname_prefix=runurl)
app.layout = dash_table.DataTable(df.to_dict('records'), [{"name": i, "id": i} for i in df.columns])
if __name__ == '__main__':
    app.run_server(port=port, host='0.0.0.0', debug=debug)

A separate method would be to separate into try: and except: which also allows you to split up the execution code depending on App/Workspace:

from dash import Dash, dash_table
import pandas as pd
import os

# Configure Dash to recognize the URL of the container
user = os.environ.get("DOMINO_PROJECT_OWNER")
project = os.environ.get("DOMINO_PROJECT_NAME")
runid = os.environ.get("DOMINO_RUN_ID")

df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/solar.csv')

try:
    runurl = '/' + user + '/' + project + '/r/notebookSession/' + runid + '/'
    app = Dash(__name__, routes_pathname_prefix='/', requests_pathname_prefix=runurl)
    app.layout = dash_table.DataTable(df.to_dict('records'), [{"name": i, "id": i} for i in df.columns])
    if __name__ == '__main__':
        app.run_server(port=8888, host='0.0.0.0', debug=True)
except:
    runurl2 = '/' + user + '/' + project + '/notebookSession/' + runid + '/proxy/8889/'
    app2 = Dash(__name__, routes_pathname_prefix='/', requests_pathname_prefix=runurl2)
    app2.layout = dash_table.DataTable(df.to_dict('records'), [{"name": i, "id": i} for i in df.columns])
    if __name__ == '__main__':
        app2.run_server(port=8889, host='0.0.0.0', debug=False)

Important note

Using debug=False when running inside a Workspace appears needed in Domino 5.