An interesting usage of this will be to deploy together with the HASingletonContoller that controls deployment of ./deploy-hasingleton, a BarrierController that subscribes for the singleton notifications in order to control an "HASingletonBarrier" mbean.

Ordinary mbean services, to be run as singletons, can then be made to <depend> on the barrier and be deployed normally to the ./farm (or ./deploy) directory. Those services will then be instated/created on all nodes, but only be started on the master node.

This provides an alternative to the deploy-hasingleton approach in that (a) we can use farming to distribute the service (b) the service will be live on all nodes, but only started on one, so it will need to make sure it does minimal or no work inside create(), rather it uses start() to do the work.