Implementation of a Customizable Fault Tolerance Framework

While there has been signiicant advances in fault tolerance research, the eeort has focused on the design of individual fault-tolerant systems or methodologies. Recently, some research has been initiated to develop fault tolerance paradigms that can be used to provide a spectrum of fault tolerance levels. In this paper, we present the design of a fault tolerance framework that can be used to support a wide spectrum of applications with various fault tolerance requirements, various criticality levels, and various system models. The framework is designed to be parameterizable so that the user can conngure it to obtain the desired features. Also, the framework is designed to be an oo-the-shelf component such that application programs can be integrated within it easily to obtain the fault-tolerant version of the application system. A specialized N-modular redundancy (SNMR) scheme has been developed to serve as the primary approach for achieving eecient and cost-eeective fault tolerance for the framework. In most cases, the SNMR scheme yields better performance and lower cost in providing fault tolerance as compared with conventional NMR schemes. It also enhances the scalability and customizability of the general replication method. This paper discusses the major concept of the SNMR framework and the main issues in the design and implementation of the framework, including an object-oriented overall system design and the interface protocol class hierarchy. The interface protocol class hierarchy provides a nice paradigm for the implementation of customizable, highly reusable, and easily extensible SNMR framework.