DIS-Broker

Introduction

This DIS-Broker is a WSRF service that adopts the singleton pattern. It provides subscription-brokering capability allowing to a client (i.e. the client part of a service) to subscribe to a topic without knowing the location of the notification producer (the Endpoint Reference identifying it). Moreover, the DIS-Broker service supports the subscription to a topic that the producer has not yet exposed. In this case, it maintains the pending subscription until the notification producer registers its topic. The implementation of this service is not based on the brokered notification schema since the DIS-Broker subscribes the consumer directly to the notification producer. In that way there is not a central service that is in charge to receive notifications from producers and to deliver them to the right client (as in the brokered notification architecture). However, the DIS-Broker continues its mediation even after the brokerage of the subscription. In fact, the DIS-Broker automatically manages the relocation of notification producers by forwarding the client subscription requests to the new instances of the producers. This service implementation supports the transparent subscription/re-subscription of the client to the new producer instances that comes up after the initial request of subscription.