Gnocchi is a multi-tenant timeseries, metrics and resources database. It provides an HTTP REST interface to create and manipulate the data. It is designed to store metrics at a very large scale while providing access to metrics and resources information to operators and users.
Gnocchi is part of the OpenStack project. While Gnocchi has support for OpenStack, it is fully able to work stand-alone.
You can read the full documentation online at http://gnocchi.xyz.