Fault tolerance AOP approach1

Object oriented systems are composed by a collection of interacting objects. Distributed object oriented systems consider that all these objects can be located at different computers connected through a network. Reliability and availability are very important trends in the development process of these kinds of systems. In order to improve these features, object replication mechanisms have been introduced. Programming replication policies for a given application is not an easy task, and this is the reason why transparency for the programmer has been one of the most important properties offered by all replication models. However, this transparency for the programmer is not always desirable. There are situations in which programmers need to manipulate by hand the replication properties. In this paper we present a replication model, JReplica, based on Aspect Oriented Programming (AOP). JReplica allows the separated specification of the replication code from the functional behaviour of objects, providing not only a high degree of transparency, as done by previous models, but also the possibility for programmers to introduce new behaviour to specify different fault tolerance requirements. Derived from the use of AOP, JReplica also obtains two important added benefits: the possibility of obtaining an ORB independent replication and the possibility of reusing entire replication policies. Moreover, the replication aspect has been introduced at design time, and in this way, UML has been extended in order to consider replication issues separately at the moment of designing fault tolerance systems.