Detecting ENF Event Predicates in Distributed Systems

Abstract

Detection of global event predicates is an important issue for distributed systems, particularly for debugging and monitoring of such systems. This paper defines event normal form (ENF) event predicates, and then provides an on-line distributed algorithm to detect the first occurrence of such a predicate. We extend the algorithm to detect parameterized predicates, and develop a multithreaded matcher that will detect multiple instances of an ENF predicate. Measurements show that the algorithm is very fast, taking 10–20 μs to process each event message, depending upon the predicate complexity. We believe that this combination of speed and flexibility can make the algorithm very useful for on-line monitoring of distributed systems.