Database admission control and request scheduling for dynamic content Web servers
Elnikety, Sameh Mohamed
Master of Science thesis
This thesis presents a method to do admission control and request scheduling for database-bound dynamic content Web servers. Our method is both transparent, requiring no modification to the software components, and external, permitting an implementation in a separate proxy. Admission control prevents overloading the database server. We implement admission control by estimating the amount of work that each request imposes on the system. A request is admitted only when it does not drive the system into overload. Request scheduling improves average response time. We exploit the variability in the workload by using shortest job first scheduling, which reorders the pending requests to reduce the average response time. We evaluate these techniques experimentally using the TPC-W benchmark. We show consistent performance during overload. Moreover, the average response time improves by up to a factor of 14, and peak throughput increases up to 10 percent.