Optimal Deployment of Eventually-Serializable Data Services

Replication is a fundamental technique for increasing throughput and achieving fault tolerance in distributed data services. However, its implementation may induce significant communication costs to maintain consistency between the replicas. Eventually-Serializable Data Service (ESDS) has been proposed to reduce these costs and enable fast operations on data, while still providing guarantees that the replicated data will eventually be consistent. This paper reconsiders the deployment phase of ESDS, in which a particular implementation of communicating software components must be mapped onto a physical architecture. This deployment aims at minimizing the overall communication costs, while satisfying the constraints imposed by the protocol. Both MIP and CP models are presented and applied to realistic ESDS instances. The experimental results indicate that both models can find optimal solutions and prove optimality; The CP model, however, provides orders of magnitude improvements in efficiency. The limitations of the MIP model and the critical aspects of the CP model are discussed. Symmetry breaking and parallel computing are also shown to bring significant benefits.