Docker Hub's rate limits are so low now that they've started to affect
my home lab. Deploying a caching proxy and directing all pull requests
through it should prevent exceeding the limit. It will also help
prevent containers from starting if access to the Internet is down, as
long as their images have been cached recently.
The `site.yml` playbook imports all of the other playbooks, providing a
way to deploy _everything_. Normally, this would only be done for a
single host, as part of its initial provisioning, to quickly apply all
common configuration and any application-specific configuration for
whatever roles the host happens to hold.
The `host-setup.yml` playbook provides an entry point for configuring
all common configuration. Basically anything we want to do to _every_
machine, regardless of its location or role.
Dustin