On interacting control loops in self-adaptive systems

Abstract

Control loops in self-adaptive systems are typically conceived as a sequence of four computations: Monitor-Analyze-Plan-Execute (MAPE). During the development of a traffic monitoring system with support for self-healing, we have noticed that simple MAPE loops are not sufficient to deal with the more complex failure scenarios. To manage the adaptations in these scenarios, we extend MAPE loops with support for two types of coordination. First, we introduce support for intra-loop coordination enabling MAPE computations within one loop to coordinate with one another. Intra-loop coordination allows the execution of multiple sub-loops within one control loop. Second, we introduce support for inter-loop coordination enabling MAPE computations across multiple loops to coordinate with one another. Inter-loop coordination allows the MAPE computations of different loops to coordinate the various phases of adaptations. We show how we used the extensions to support self-healing in the traffic monitoring system. We discuss an implementation framework that supports coordination of MAPE loops, and from our experiences offer recommendations for future research in this area.