The Complexity of Adding Failsafe Fault-Tolerance

In this paper, we focus our attention on the problem of automating the addition of failsafe fault-tolerance where fault-tolerance is added to an existing (fault-intolerant) program. A failsafe faulttolerant program satisfies its specification (including safety and liveness) in the absence of faults. And, in the presence of faults, it satisfies its safety specification. We present a somewhat unexpected result that, in general, the problem of adding failsafe fault-tolerance in distributed programs is NP-hard. Towards this end, we reduce the 3-SAT problem to the problem of adding failsafe fault-tolerance. We also identify a class of specifications, monotonic specifications and a class of programs, monotonic programs. Given a monotonic specification and a monotonic program, we show that failsafe fault-tolerance can be added in polynomial time. We note that the monotonicity restrictions are met for commonly encountered problems such as Byzantine agreement, distributed consensus, and...

• Type: Conference
• Year: 2002
• Where: ICDCS
• Authors: Sandeep S. Kulkarni, Ali Ebnenasir
• Keywords: Distributed And Parallel Computing, Distributed Programs, Failsafe Fault-tolerance, Failsafe Faulttolerant Program, ICDCS 2002