An admission control scheme for predictable server response time for web accesses

The diversity in web object types and their resource requirements contributes to the unpredictability of web service provisioning. In this paper, an efficient admission control algorithm, PACERS, is proposed to provide different levels of services based on the server workload characteristics. Service quality is ensured by periodical allocation of system resources based on the estimation of request rate and service requirements of prioritized tasks. Admission of lower priority tasks is restricted during high load periods to prevent denial-of-services to high priority tasks. A double-queue structure is implemented to reduce the effects of estimation inaccuracy and to utilize the spare capacity of the server, thus increasing the system throughput. Response delays of the high priority tasks are bounded by the length of the prediction period. Theoretical analysis and experimental study show that the PACERS algorithm provides desirable throughput and bounded response delay to the prioritized tasks, without any significant impact on the aggregate throughput of the system under various workload.