Status Updates From Docker in Action

Docker handles configs of an application in an interesting way. In a Docker stack, they are treated as resources, just like networks, services, and volumes. So they can vary independent of the main application, giving it flexibility in different deployment environments.
There's also secrets that are just like configs, except they're only accessible by the appropriate services. This way, you can manage them safely.

A "compose file" is like a full declarative description of the environment you want to build, and then you can use "docker stack" to build it. Docker will take care of the rest.
Also, the use of dedicated internal networks to abstract services as an interface of replicated containers was very interesting.

Docker services are very interesting. You can abstract a number of containers into a service, and then Docker Swarm takes care of all the stuff, like replication or rolling out to a new version.