Lightweight Fault Tolerance in CORBA

Although fault-tolerant implementations of CORBA have been available for several years, the standard specification of fault-tolerant CORBA (FT-CORBA) has been finalized only recently. This specification defines simple, minimal mechanisms for regular clients to deal with fault-tolerant servers, as well as a wide spectrum of services and APIs for implementing replicated, fault-tolerant servers. While extremely powerful, these advanced server-side mechanisms come with significant complexity both for the FT-CORBA implementor and the application developer. This paper proposes an alternative, lightweight approach to fault tolerance for applications that do not have strong requirements in terms of data consistency. This approach builds on the client-side mechanisms of FT-CORBA and takes advantage of semantic knowledge of the server objects to mediate distributed interactions in an efficient and fault-tolerant manner. Although the approach proposed in this paper is not applicable to any application, it can be deployed in existing systems to transparently increase their reliability and availability without requiring any re-engineering.