Detecting global predicates in distributed systems with clocks [chapter]

Scott D. Stoller
1997 Lecture Notes in Computer Science  
This paper proposes a framework for detecting global state predicates in systems of processes with approximately-synchronized real-time clocks. Timestamps from these clocks are used to de ne two orderings on events: de nitely occurred before" and possibly occurred before". These orderings lead naturally to de nitions of 3 distinct detection modalities, i.e., 3 meanings of predicate held during a computation", namely: Poss db ! possibly held", Def db ! de nitely held", and Inst de nitely held in
more » ... a speci c global state". This paper de nes these modalities and gives e cient algorithms for detecting them. The algorithms are based on algorithms of Garg and Waldecker, Alagar and Venkatesan, Cooper and Marzullo, and Fromentin and Raynal. Complexity analysis shows that under reasonable assumptions, these real-time-clock-based detection algorithms are less expensive than detection algorithms based on Lamport's happened-before ordering. Sample applications are given to illustrate the bene ts of this approach.
doi:10.1007/bfb0030684 fatcat:xmg5ovmznffsjhbwj3ilidnlya