Streamlit app running inside Docker doesn't show logs

Summary

I can’t seem to manage to get logging working when running a streamlit app inside Docker. Neither logging calls nor prints are not shown on console or with docker logs.

Steps to reproduce

1. Clone [e-mail]:danimateos/streamlitdockerlog.git, cd into directory

2. Docker build

docker build -t strtest:latest .

1. Docker run

docker run -p 80:8501  strtest:latest

1. Go to localhost on browser.

2. Watch docker logs:

docker logs [your_container_name]

Expected behavior:

Three lines appear in the docker logs each time the browser tab is reloaded because of the following code in app.py:

logging.info('info')
logging.error('error')
print('print')

Actual behavior:

Nothing appears with docker logs. When the app is run with streamlit run app.py, the three lines do appear.

Is this a regression?

Not that I know.

Debug info

• Streamlit version: 0.58
• Python version: 3.8.2
• Using Conda? Yes, as described in the Dockerfile
• OS version: Ubuntu 20.04
• Browser version: Chrome version 81.0.4044.122 (Official Build) (64-bit)

Additional information

Possibly related to #1321 or #447

[MarcSkovMadsen]

Do you have

ENV PYTHONUNBUFFERED=1

in your Dockerfile @danimateos ? You will need that. I don’t exactly understand why but I once spent a lot of time investigating why “kubernetes did not give me logs back” from a Python docker image 😃

Maybe you need to add

ENV PYTHONIOENCODING=UTF-8

[danimateos]

Hi! Any news on this! I would really like to be able to keep track of how people are using my web app…