Designing Autonomic Management Systems by Using Reactive Control Techniques

The ever growing complexity of software systems has led to the emergence of automated solutions for their management. The software assigned to this work is usually called an Autonomic Management System (AMS). It is ordinarily designed as a composition of several managers, which are pieces of software evaluating the dynamics of the system under management through measurements (e.g., workload, memory usage), taking decisions, and acting upon it so that it stays in a set of acceptable operating states. However, careless combination of managers may lead to inconsistencies in the taken decisions, and classical approaches dealing with these coordination problems often rely on intricate and ad hoc solutions. To tackle this problem, we take a global view and underscore that AMSs are intrinsically reactive, as they react to flows of monitoring data by emitting flows of reconfiguration actions. Therefore we propose a new approach for the design of AMSs, based on synchronous programming and discrete controller synthesis techniques. They provide us with high-level languages for modeling the system to manage, as well as means for statically guaranteeing the absence of logical coordination problems. Hence, they suit our main contribution, which is to obtain guarantees at design time about the absence of logical inconsistencies in the taken decisions. We detail our approach, illustrate it by designing an AMS for a realistic multi-tier application, and evaluate its practicality with an implementation.