Why Flask logger does not log in docker when using UWSGI in front?

Question

I have a Flask application inside of Docker that was logging into docker logs when it was running without UWSGI in front. Now

Answer 1

I had a similar problem (Special: I wanted to use the syslog). First I had to add a rule to the Dockerfile:

RUN apt-get install -y rsyslog
service rsyslog start

Flask comes with build-in logging, so I just had to add some twigs

from flask import Flask
import logging
import logging.handlers

handler = logging.handlers.SysLogHandler(address = '/dev/log')
handler.setFormatter(logging.Formatter('flask [%(levelname)s] %(message)s'))

app = Flask(__name__)
app.logger.addHandler(handler)

Additional settings can be handled through the syslog-daemon