I am using CoreOS which uses systemd and docker.
One of the big issues with systemd and CoreOS is that it doesn't play 100% nice with docker. Or maybe docker doesn't play 100% nice either. Another issue I'm having with it is that log events that get logged in the journal appear to come from "docker" which is not true. They come from the process that docker runs. This wouldn't normally be a huge problem, but when you forward these logs onto another service like an ELK stack, you can't figure out what are nginx logs vs other service logs. Their source is all docker!
Is there a way of getting around this? I'm using docker 1.9 which is what CoreOS Stable has. So I do not have the privilege as yet of using json output from docker directly.