The selection notification allows you to register a callback method for a BrokerClusterPublisher that will be invoked whenever a Broker client needs to be chosen from the Broker cluster publisher pool for executing the operation. In the absence of any registered selection callback, BrokerClusterPublisher employs a round robin algorithm to choose Broker client from the Broker cluster publisher pool. If you want to enforce a certain order or an algorithm for choosing a Broker client, you can register a selection callback object that will be invoked just before choosing a Broker client for a publish/deliver operation.