Registration is a process where an agent on the server sends out a message on to the collective.registration.agent topic every registerinterval period. The default registration agent AgentList sends out a list of the MCollective agents installed and running in mcollectived .
In a default installation, every server publishes these registration messages, but no listener subscribes to them. I believe the original use was intended to simply keep the TCP connection alive in the presence of connection-tracking firewalls. Now that this is handled by the heartbeat support in STOMP 1.1+ protocol, registration ... well, ithas found its own reason to live.
Many people have started doing useful things with the registration agent. Let’s show you how to build your own agent and your own collector to grab that data and do something with it.