Detecting Global Predicates in Distributed Systems with Clocks

. This paper proposes a framework for predicate detection in systems of processes with approximately-synchronized real-time clocks. Timestamps from these clocks are used to define two orderings on events: "definitely occurred before" and "possibly occurred before". These orderings lead naturally to definitions of 3 distinct detection modalities, i.e., 3 meanings of "predicate \Phi held during a computation", namely: PossT \Phi ("\Phi possibly held"), DefT \Phi ("\Phi definitely held"), and Inst \Phi ("\Phi definitely held at a specific instant"). This paper defines these modalities and gives efficient algorithms for detecting them; the algorithms are based on algorithms of Cooper and Marzullo, Garg and Waldecker, and Fromentin and Raynal. Keywords: global predicate detection, consistent global states, partiallysynchronous systems, distributed debugging, real-time monitoring 1 Introduction A history of a distributed system can be modeled as a sequence of events in their order of occ..