* {@link ClusterSingletonService} by service group identifier. Services could be Applications or RPCs.
* Provider provides a functionality which allows to have only one fully instantiated service instance
* in a cluster at one time and service group means to have all service instances for the same group
* {@link ClusterSingletonService} by service group identifier. Services could be Applications or RPCs.
* Provider provides a functionality which allows to have only one fully instantiated service instance
* in a cluster at one time and service group means to have all service instances for the same group
* closed prior to relinquishing service group ownership. To achieve ownership of the service group,
* a service group candidate must hold ownership of both these entities.
*/
* closed prior to relinquishing service group ownership. To achieve ownership of the service group,
* a service group candidate must hold ownership of both these entities.
*/