CloudKitty is a Rating-as-a-Service project for OpenStack and more. The project aims at being a generic solution for the chargeback and rating of a cloud. Historically, it was only possible to operate it inside of an OpenStack context, but it is now possible to run CloudKitty in standalone mode.
CloudKitty allows to do metric-based rating: it polls endpoints in order to retrieve measures and metadata about specific metrics, applies rating rules to the collected data and pushes the rated data to its storage backend.
CloudKitty is highly modular, which makes it easy to add new features.