Architectural Availability Analysis of Software Decomposition for Local Recovery

Non-functional properties, such as timeliness, resource consumption and reliability are of crucial importance for today’s software systems. Therefore, it is important to know the non-functional behavior before the system is put into operation. Preferably, such properties should be analyzed at design time, at an architectural level, so that changes can be made early in the system development process. In this paper, we present an efficient and easy-to-use methodology to predict – at design time – the availability of systems that support local recovery. Our analysis techniques work at the architectural level, where the software designer simply inputs the software modules’ decomposition annotated with failure and repair rates. From this decomposition we automatically generate an analytical model (i.e. a continuous-time Markov chain), from which various performance and dependability measures are then computed, in a way that is completely transparent to the user. A crucial step is the use of intermediate models in the Input/Output Interactive Markov Chain formalism, which makes our techniques, efficient, mathematically rigorous, and easy to adapt. In particular, we use aggressive minimization techniques to keep the size of the generated state spaces small. We have applied our methodology on a realistic case study, namely the MPlayer open source software. We have investigated four different decomposition alternatives and compared our analytical results with the measured availability on a running MPlayer. We found that our predicted results closely match the measured ones.