Multi-class Latency Bounded Web Services

Abstract

Two recent advances have resulted in significant improvements in web server quality-of-service. First, both centralized and distributed web servers can provide isolation among service classes by fairly distributing system resources. Second, session admission control can protect classes from performance degradation due to overload. The goal of this thesis is to design a general "front-end" algorithm that uses these two building blocks to support a new web service model, namely, multi-class services which control response latencies to within pre-specified targets. Our key technique is to devise a general service abstraction to adaptively control not only the latency of a particular class, but also to assess the inter-class relationships. In this way, we capture the extent to which classes are isolated or share system resources (as determined by the server architecture and system internals) and hence their effects on each other's QoS. We validate the scheme with trace driven simulations.