Approaches for increasing availability of component-based traffic management software

For today´s traffic management and control systems, availability (defined as the degree to which a system is operable at any given point in time) is of increasing importance. This concerns on one hand hardware and on the other hand software. While in case of a failure in a hardware circuit, a watchdog resets the faulty control-unit, for the monitoring of software, patterns like the Watchdog Pattern, the Safety Executive Pattern or improvements to them might be applied. As these patterns primarily target the monitoring of a single software component running on one node, extensions are necessary that allow supervising complex, multi-threaded components and, thus, fully distributed applications. This paper presents two approaches applicable to the domain of Variable Message Signs (VMS). Both solutions make use of the Web-Based Enterprise Management (WBEM) technology to acquire status information of the underlying multi-threaded components, and to start-up the system whenever necessary. For a proof-of-concept implementation the Windows Management Instrumentation (WMI) has been applied.