QoS-aware fully decentralized service assembly

Large distributed software systems are increasingly common in today geographically distributed IT infrastructures. A key challenge for the software engineering community is how to efficiently and effectively manage such complex systems. Extending software services with autonomic capabilities has been suggested as a possible way to address this challenge. Ideally, self-management capabilities should be based on fully distributed, peer-to-peer (P2P) architectures in order to try to overcome the scalability and robustness problems of centralized solutions. Within this context, we propose an approach for the adaptive self-assembly of distributed services, based on a simple epidemic protocol. Our approach is based on the three-layer reference model for adaptive systems, and is centered on the use of a gossip protocol to achieve decentralized information dissemination and decision making. The goal of our system is to build and maintain an assembly of services that, besides functional requirements, is able to fulfill global quality of service (QoS) and structural requirements. A set of simulation experiments is used to assess the effectiveness of our approach in terms of convergence speed towards the optimal solution, and resilience to failures.