The Corosync Cluster Engine is a Group Communication System with
additional features for implementing high availability within
applications. The project provides four C Application Programming
Interface features:

 * A closed process group communication model with virtual synchrony
   guarantees for creating replicated state machines.
 * A simple availability manager that restarts the application process
   when it has failed.
 * A configuration and statistics in-memory database that provide the
   ability to set, retrieve, and receive change notifications of
   information.
 * A quorum system that notifies applications when quorum is achieved
   or lost.