Coarse Grained Web Service Availability, Consistency, and Durability

In this paper we investigate the problem of providing consistency, availability and durability for Web Service-transactions. We consider each transaction as a black box, with only the corresponding metadata, expressed as UML specifications, as transaction semantics. We refer to these WS transactions as coarse-grained WS-transactions. We propose an approach that guarantees the availability of the popular lazy replica update propagation method while increasing the durability and consistency. In our previous work, we proposed a replica update propagation method, called Buddy System, which required that updates are preserved synchronously in two replicas. In this paper we extend the Buddy System to handle course grained WS transactions, using UML stereotypes that allow scheduling semantics to be embedded into the design model. This design model is then exported and consumed by a service dispatcher to provide: 1.) High availability by distributing service requests across all available clusters. 2.) Consistency by performing the complete transaction on a single set of clusters. 3.) Durability by updating two clusters synchronously.