A Model for Worldwide Tracking of Distributed Objects

We describe a service for locating distributed objects identified by location-independent object identifiers. An object in our model is physically distributed, with multiple active copies on different machines. Processes must bind to an object in order to invoke its methods. Part of the binding protocol is concerned with contacting the object, which offers one or more contact points. A contact point is associated with an active part of the distributed object, and describes exactly how and where initial communication should take place. An object can change its contact points in the course of time, thus exhibiting migration behavior. Finding an object’s contact points is the essence of our location service. Our model is based on a worldwide distributed search tree, capable of handling trillions of distributed objects. The tree adapts dynamically to individual migration patterns. By exploiting an object’s relative stability with respect to a region, combined with the use of pointer caches, an object can be contacted through a search path of only length two. We present the architecture of our location service, including its update and lookup mechanism, and discuss its scalability.