To the other responses I'll add that very often the right model is to compose containers within a system, not processes within a container. Most of the OP's con

To the other responses I'll add that very often the right model is to compose containers within a system, not processes within a container. Most of the OP's concerns in this area stem from the basic misconception that containers are sort of like VMs, and so it's sort of wasteful to only run a single process in one. Containers are very lightweight jails to run a process in, and all the containers running on a system can communicate with each other over the docker bridge with one hop.