Using QoS Contracts to Drive Architecture-Centic Self-Adaptation

Abstract : Self-adaptation is now a promising approach to maximize the satisfaction of requirements under changing environmental conditions. One of the key challenges for such self-adaptive systems is to automatically find a relevant architectural configuration. Existing approaches requires a set of adaptation strategies and the rough estimation of their side-effects. However, due to the lack of validation methods for such strategies and side-effects, existing approaches may lead to erroneous adaptations. Instead of side-effects, our solution leverages quality contracts whose accuracy can be separately established and which can be dynamically composed to get a quality prediction of any possible architectural configurations. To support self-adaptation, we propose a reactive planning algorithm which exploits quality contracts to dynamically discover unforeseen architectural configurations. We illustrate our approach using a running HTTP server adapting its architecture with respect to the number and the similarity of incoming requests.