SLA Based Profit Optimization in Web Systems

With the rapid growth of eBusiness, the Web services are becoming a commodity. To reduce the management cost for the IT infrastructure, companies often outsource their IT services to third party service providers. Large service centers have been set up to provide services to many customers by sharing the IT resources. This leads to the efficient use of resources and a reduction of the operating cost. The service provider and their customers often negotiate utility based Service Level Agreements (SLAs) to determine the cost and penalty based on the achieved performance level. The system is based on a centralized controller which can control the request volumes at various servers and the scheduling policy at each server. The controller can also decide to turn ON or OFF servers depending on the system load. This paper designs a resource allocation scheduler for such web environments so as to maximize the profits associated with multiple class SLAs. We consider a realistic utility function for the profits, which depends on the level of achieved service quality in a non-linear way. We show that the overall problem is NP-hard, and develop meta-heuristic solutions based on the tabu-search algorithm. Experimental results are presented to show the benefits of our approach.