Adaptive Admission Control for Web Applications With Variable Capacity

The system capacity available to a multi-tier Web based application is often a dynamic quantity. Most static threshold-based overload control mechanisms are best suited to situations where the system's capacity is constant or the bottleneck resource is known. However, with varying capacity, the admission control mechanism needs to adapt dynamically. The authors propose and implement an adaptive admission control mechanism that adjusts the admitted load to compensate for changes in system capacity. The proposed solution is implemented as a proxy server between clients and front-end Web servers. The proxy monitors 'Black-box' performance metrics - response time and rate of successfully completed requests (good-put).