ROAFTS: a middleware architecture for real-time object-oriented adaptive fault tolerance support

A middleware architecture named ROAFTS (Real-time Object-oriented Adaptive Fault Tolerance Support) is presented. ROAFTS is designed to support adaptive fault-tolerant execution of not only conventional process-structured distributed real-time (RT) application software but also new-style object-structured distributed RT application software. While ROAFTS contains fault tolerance schemes devised for quantitatively guaranteed RT fault tolerance, it is also designed to relax that characteristic while the application is in a soft RT phase in order to reduce resource use. Through three different prototype implementation experiences using both commercial operating system kernels and home-grown RT kernels, the middleware architecture has been refined and its basic capabilities and effectiveness have been validated. The fault tolerance schemes supported and the integrating architecture are discussed in this paper. Implementation experiences and some future tasks are also discussed.