Revenue Optimization of Service Compositions Using Conditional Request Retries

Due to the inherent stochastic nature of services execution environment within service oriented systems, a runtime adaptation of the given composition may be required. We address a runtime service adaptation mechanism based on conditional retries for the orchestrated web services. The conditional retry may be issued while a concrete service within composition is executed. The retry could either invoke the same concrete service or a functionally equivalent web service that implements the same task. We use dynamic programming to determine the optimal time instances at which the current request should be terminated before request replication. The calculation takes into account different QoS parameters like services´ response -- time distributions and cost - relating parameters, and the solution optimizes the expected revenue of composite service provider. We illustrate the benefits of our approach by numerical calculations, and discuss the impact of considered QoS parameters to the solution at hand.