The Merlin project, or Module for Effortless Redundancy and Loadbalancing In Nagios, was initially started to create an easy way to set up distributed Nagios installations, allowing Nagios processes to exchange information directly as an alternative to the standard nagios way using NSCA. When starting the Ninja project we realised that we could continue the work on Merlin and adopt the project to function as backend for Ninja by adding support for storing the status information in a database, fault tolearance and some other cool things. This means that Merlin now are responsible for providing status data, acting as a backend, for the Ninja GUI.
merlin-mod: Responsible for jacking into the NEBCALLBAC_* calls and send them to a socket. If the socket is not available the events are written to a backlog and sent when the socket is available again.
merlind: The Merlin deamon listens to the socket that merlin-mod writes to and sends all events received either to a database of your choise (using libdbi) or to another merlin daemon. If the daemon is unsuccessful in this it writes to a backlog and sends the data later.
merlin database: This is a database that includes Nagios object status and status changes. It also contains comments, scheduled downtime etc.
It is easy to get involved in the Merlin project and to contribute!
Here is the available information about the Merlin project