Beernet: RMI-free peer-to-peer networks

The key issue in distributed programming is partial failure: how to handle failures of part of the system. This unavoidable property causes uncertainty because we cannot know whether a remote object is ever going to reply to a message. It is also the reason why RMI/RPC is difficult to use. In this paper we describe the most convenient object-oriented mechanism we have found to develop peer-to-peer applications effectively, namely by using active objects that communicate via asynchronous message passing and fault streams for failure handling. We show that this works better than the usual approach of using RMI to communicate and distributed exceptions for failure handling. We define our peers as lightweight actors and we use them to build a highly dynamic peer-to-peer network that deals well with partial failure and non-transitive connectivity. We give many code examples to show the simplicity and naturalness of our approach.