Opa is a concise and elegant language for writing distributed web applications.

CloudStack is open source software written in java that is designed to deploy and and manage large networks of virtual machines, as a highly available, scalable cloud computing platform. CloudStack current supports the most popular open source hypervisors VMware, Oracle VM, KVM, XenServer and Xen Cloud Platform. CloudStack offers three ways to manage cloud computing environments: a easy-to-use web interface, command line and a full-featured RESTful API.