A QoS-Aware Middleware for Dynamic and Adaptive Service Execution ⋆
Chen Wang · 2011
Abstract. Service-Oriented Architecture (SOA) provides a flexible solution for building loosely coupled distributed applications. Complex applications can be designed by defining a business process that composes a set of independent software modules called services. In this scenario, each service can be selected and bound dynamically at run-time among a set of candidates that provide the same functionality but differs in quality of service (QoS). However, the QoS values advertised by partner services are not always ensured at run-time. In response to the dynamic execution environment, the execution of a business process has to be adapted onthe-fly in case that a global QoS violation is predicted. In this paper, we introduce a QoS-aware middleware system for dynamic and adaptive service execution. The run-time service selection is modeled as an optimization problem based on user’s end-to-end QoS constraints and preferences on the service composition level. In contrast to the centralized execution engine adopted by most of traditional approaches, the execution of a service composition is decentralized in the middleware. Moreover, Program Evaluation and Review Technique (PERT) and Heartbeat Failure Detector (HB) are introduced as effective approaches to predict global QoS violations and draw appropriate adaptation decisions. 1