Kubernetes log not showing output of python print method

Question

I've a python application in which I'm using print() method tho show text to a user. When I interact with this application manually using kubectl exec ... command I can see the output of prints.

However, when script is executed automatically on container startup with CMD python3 /src/my_app.py (last entry in Dockerfile) then, the prints are gone (not shown in kubectl logs). Ayn suggestin on how to fix it?

Crou · Accepted Answer · 2020-01-29 16:06:18Z

5

This is because stdout and stderr streams are buffered in Python.

You can set the Environment variable to PYTHONUNBUFFERED=1 or True

Also you could use -u option in your Dockerfile.

-u

Force the stdout and stderr streams to be unbuffered. This option has no effect on the stdin stream.

Changed in version 3.7: The text layer of the stdout and stderr streams now is unbuffered.

answered Jan 29, 2020 at 16:06

Crou

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Lukasz Dynowski · Accepted Answer · 2020-01-29 15:00:21Z

3

It turned out to be a problem of python environment. Setting, these two environment variables PYTHONUNBUFFERED=1 and PYTHONIOENCODING=UTF-8 fixed the issue.

answered Jan 29, 2020 at 15:00

Lukasz Dynowski

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