Near-optimal configuration of service pool size in service composition

To improve the reliability of service composition, service pools with redundant services are often registered in advance. Increasing the number of redundant services in a pool could improve the reliability while decreasing the performance or increasing unnecessary cost. Aiming at minimizing the overall cost or response time under certain reliability constraint, this paper proposed a service pool size choosing method from the point of view of service composition. It started with the reliability and performance evaluation of single service pool with multiple services and then employed architecture-based model to obtain the overall reliability/performance model for service composition with multiple service pools. These models were used as the utility function and constraint function to optimize service pool size combination. Two sensitivity-based algorithms were proposed to solve the optimization problem, which assigned more redundant services to those service pools that have higher impact on reliability change and lower impact on performance change. Empirical studies results showed that these algorithms could find the near-optimal size combination of service pools using much less time than the exhaustive iteration method.