Distributed Programming using Object-Groups

Many of today's object-oriented distributed toolkits focus on transactions to synchronize distributed applications. Transaction mechanisms are well suited for synchronizing data-oriented applications. In contrast directly distributed systems, like various kinds of failure tolerant client-server applications, often require a much finer degree of synchronization. Such a fine degree of synchronization is realizable by means of reliable process-group multicast, causal communication, and message passing mechanisms. However, toolkits offering these capabilities, for example Isis or Horus, are often lowlevel and therefore difficult to program. Therefore, we propose three object-oriented abstraction mechanisms, namely object groups, Remote Method Calling, and Smart Proxies. We argue that the abstractions are powerful enough to encapsulate processgroups, reliable multicast, and asynchronous message passing. Examples of how the abstractions are being realized in a prototype toolkit called Elect..