--autoreload preventing server launch in Flask web app

Panel
,
1

I don’t know if the title of the issue is accurate because it can be less obvious than it appears but I have no idea of what is causing that.

I’m trying to debug a single page web app developped with Flask and Panel. It has been containerized with Docker.

I’m using this command to launch it :

python -m panel serve --port=8080 --address=0.0.0.0 --websocket-max-message-size=100000000 app.py

and it works fine, i’m getting the output as expected:

2022-03-25 08:26:32,495 Starting Bokeh server version 2.4.2 (running on Tornado 6.1)
2022-03-25 08:26:32,496 Torndado websocket_max_message_size set to 100000000 bytes (95.37 MB)
2022-03-25 08:26:32,496 User authentication hooks NOT provided (default user enabled)
2022-03-25 08:26:32,498 Bokeh app running at: http://0.0.0.0:8080/app
2022-03-25 08:26:32,498 Starting Bokeh server with process id: 39

Issue
However when i add the --autoreload option to the panel serve command I get:

Launching server at http://localhost:38647

And nothing happens…

ALL software version info

  • python 3.8
    • matplotlib 3.5.1
    • panel 0.12.6
    • bokeh 2.4.2
    • holoviews 1.14.8
    • datashader 0.13.0
    • hvplot 0.7.3
    • shapely 1.8.1.post1
    • xarray 2022.3.0
    • h5netcdf 0.15.0
    • scipy 1.8.0
    • requests 2.27.1
    • spatialpandas 0.4.3
    • jinja2 3.0.2
  • Debian GNU/Linux 11

Dockerfile

FROM python:3.8

RUN apt-get update && apt-get install -y libgeos-dev

COPY requirements.*txt /tmp/
RUN pip install --no-cache-dir -r /tmp/requirements.txt

WORKDIR /usr/src/app
COPY app.py .

ENTRYPOINT python -m panel serve --port=8080 --address=0.0.0.0 --websocket-max-message-size=100000000 app.py

Do you have an idea of what is happening ?

Thank you for your help !

1 Like
2

The thing I notice is that the ports are different (38647 and 8080). The command running the container needs to open/ expose the relevant port. Did you do that?

3

Yes I’m building the app through a docker-compose.yml:

version: '3'
services:
  panel_app:
    build:
      context: .
      dockerfile: single_page_webapp.Dockerfile
    env_file: ${PANEL_CONFIG}
    expose: 
      - 8080
    ports:
      - "8080:8080"
    volumes:
      - .:/usr/src/app

And yes I don’t really understand why the app is deployed at port 38647

4

It could be because app.py has a “.show()” on one of the widgets.

5

I’m not using .show() in the app.py

6

It is hard to say without knowing what is inside app.py. Can you see if the problem is still there if you change app.py to:

import panel as pn
pn.panel("Hello").servable()
1 Like
7

Ok it works in this case with app.py:

import panel as pn
pn.panel("Hello").servable()

Thank you for your help, I need to investigate that

2 Likes