Problem with logging in docker when using fluentd for logging of three flask apps running in a docker network behind an nginx
I finally found out the problem: the fluent container needs some time to start up; because it's started with --detach the subsequent containers try to connect before fluentd is actually running, only the 3rd instance of the flask application connects when fluentd is already up. So, delaying the startup of the remaining containers solves my problem.