Long Live Continuous Consensus

Abstract

Fault-tolerant systems often require a means by which independent processes or processors can arrive at an exact mutual agreement of some kind. The work announced in this note studies the continuous consensus problem, which is a general tool for enabling actions that are performed at the same time at different sites of the system to be consistent with one another (e.g., mutual exlusion, firing squad etc). Suppose that we are interested in maintaining a simultaneously consistent view regarding a set of events E in the system. These are applicationdependent, but will typically record inputs that processes receive at various times, values that certain variables have at a given time, and faulty behavior in the form of failed or inconsistent message deliveries. A continuous consensus (CC) protocol maintains at all times k ≥ 0 a core M _i [k] of events of ε at every site i. In every run of this protocol the following three properties are required to hold, for all nonfaulty processes i and j.