PARSY: Performance Aware Reconfiguration of Software Systems

Dynamic reconfiguration of component-based systems is recognized as a viable way to meet quality requirements in a mutable operating environment. In this paper we consider the problem of maintaining the overall response time of a component-basedsystem below a given threshold, as the system is subject to variable workload. We assume that the system components can be dynamically reconfigured to provide a degraded service with lower response time. Each component operating at one of the available quality levels is assigned a utility, with higher quality levels associated to higher utilities. The main contribution of this paper is an on-line algorithm for performance-aware reconfiguration of degradable software systems called PARSY (Performance Aware Reconfiguration of software SYstems). PARSY tunes individual components in order to maximize the system utility with the constraint of keeping the system response time below a specific threshold. PARSY drives the runtime dynamic reconfiguration step with the help of a Queueing Network performance model. Numerical experiments are used to illustrate the effectiveness of the proposed approach.