— Managing the performance of multiple-tiered Web sites under high client loads is a critical problem with the advent of dynamic content and database-driven servers on the Internet. This paper presents a control-theoretic approach for admission control in multi-tiered Web sites that both prevents overload and enforces absolute client response times, while still maintaining high throughput under load. We use classical control theoretic techniques to design a Proportional Integral (PI) controller for admission control of client HTTP requests. In addition, we present a processor-sharing model that is used to make the controller self-tuning, so that no parameter setting is required beyond a target response time. Our controller is implemented as a proxy, called Yaksha, which operates by taking simple external measurements of the client response times. Our design is non-invasive and requires minimal operator intervention. We evaluate our techniques experimentally using a 3-tiered dynamic c...
Abhinav Kamra, Vishal Misra, Erich M. Nahum