The complexity of adding failsafe fault-tolerance

S.S. Kulkarni, A. Ebnenasir
Proceedings 22nd International Conference on Distributed Computing Systems  
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
more » ... 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 atomic commitment. Finally, we argue that the restrictions on the specifications and programs are necessary to add failsafe faulttolerance in polynomial time; we prove that if only one of these conditions is satisfied, the addition of failsafe fault-tolerance is still NP-hard.
doi:10.1109/icdcs.2002.1022271 dblp:conf/icdcs/KulkarniE02 fatcat:kojmsv3ry5cnrhu7kasigmtjuu