Graylog (graypy) + Docker
Docker is able to send logs from its standart output into graylog using gelf logger:
https://docs.docker.com/config/containers/logging/gelf/
When you dockerize your app, your app's localhost is not localhost of host machine. Simply remove all your fancy gelf-logger-libs from your python-code and put logs to stdout. Then docker will catch your logs and will send it to the graylog host.