An availability system is provided that includes a hierarchy of controllers for providing event notifications relating to availability of components of a scalable MPP system. A controller receives a subscription from a child controller that identifies an event type and a generator. The controller stores in a subscription store an indication that the subscription has been received from the child controller. When a parent controller has not yet been notified of a subscription with a matching event type and generator as indicated by the subscription store, the controller sends the subscription to the parent controller. When the parent controller has already been notified of a subscription with a matching event type and generator as indicated by the subscription store, the controller suppresses the sending of the subscription to the parent controller.