Having fun with Etcd
Etcd is a distributed, consistent key-value store for shared configuration and service discovery, with a focus on being. Etcd is very useful in DevOps context because today Immutable Infrastructure is one of the core principles. Often what people do is store the configs into a K/V store like Etcd and them just export OS_VARS into the OS level that could be an Amazon AMI, Linux or Bare metal, Mesos or even a Docker container. One of the cool things about Etcd is that you have a pretty simple REST interface to operate over the K/V store. When you are doing provisioning sometimes you need store IPs, IDS, Tags, etc... and this is very viable solution.