I have one nginx container to just route traffic to the other web and worker containers. As I have 16 of those in total. 8 web processes with 4 puma workers in each and then 8 sidekiq processes with a bunch of workers in those.
Just saw this now :)
We actually don't have one application process. But that's beside the point. Using docker at the time for us was absolutely overkill and you could easily do this with vms.
However, the main reason for doing this was to get ready for situations in the future when this would change. And this situation happened two months ago and at that point I was really happy we were on a solution like this.
DCHQ provides me with a managed building platform that allow me to manage everything in a web interface, but it is absolutely overkill for our use of the system as they are capable of so much more.
I hope that explains it better.