This paper presents a framework to support dynamic adaptation of applications, which consists of a reusable infrastructure with standard elements to monitor and adapt running applications, and a contract-based adaptation language to enable one to express high-level adaptation policies. The proposed framework is used to introduce dynamic adaptation capabilities into a server cluster infrastructure, intended to address power and performance management concerns. By experimental evaluation, we demonstrate that our approach is useful and effective in providing the required support for describing and deploying typical power management contracts.