What service replication middleware can learn from object replication middleware

Replication is a well-known technique to enhance dependability and performance in distributed systems. A plethora of replication middleware for distributed object systems has been proposed in the past decade. However, replication in service-oriented systems is still in its infancy. In this paper, we analyze some of the proposed service replication middleware solutions and compare them on an architectural level with object replication middleware. In particular, we focus on replication middleware that allows for (but is not limited to) strict consistency of replicas since this is required by many real-life applications. We identify six major infrastructure components and present a generalized architecture for both distributed object and service-oriented replication middleware. The result of our comparison is unambiguous: Replication middleware for service-oriented systems and distributed object systems (such as FT-CORBA) share many commonalities and only subtle differences caused by the different granularity of the replicated entity, or different transaction models.