The LoadBalancingContext object

All DefaultBackgroundTaskLoadBalancingPlugin methods require that you pass a LoadBalancingContext object as you execute the method. Public interface LoadBalancingContext provides the following methods.

Method Returns Description
getAllComponents() List<ComponentInfo> Method returns a list of all components running in the cluster.
requestTransferToThisServer(component) Boolean Method requests the transfer of the given component to this server. Use the getAllComponents and the ComponentInfo.getServerId methods to obtain the current owner of a component.

The component transfer itself is an asynchronous process. This method returns true if the transfer request completed successfully, which does not mean the transfer itself completed successfully.
isAllowedToStartOnThisServer(component) Boolean Method returns true if it is possible to start the given component on the current server.
getTransferInfo(component, unit, timeout) TransferInfo Given a specific component (component), the method returns information on the component transfer or null if the transfer attempt timed out.

Parameters timeout and unit provide the time to wait before the transfer request times out.
scheduleComponentAvailabilityCheck(delay, unit) -- Method schedules a component availability check. If a component is available to start, this method calls either of the following methods on the BackgroundTaskLoadBalancingPlugin plugin:
  • selectMessageDestinationsToStartNow
  • selectStartablePluginsToStartNow

Parameters delay and unit provide the time to wait before performing the availability check.
The return TransferInfo object has two useful methods:
  • getCurrentOwner - Method returns the current owner of the component. If the method returns null, it means that the component is already stopped.
  • getTargetOwner - Method returns the owner of the target component. It cannot return null.