Why Logical Clocks Are Easy

Tracking causality should not be ignored. It is important in the design of many distributed algorithms. And not respecting causality can lead to strange behaviors for users. The most commonly used mechanisms for tracking causality, vector clocks and version vectors, are simply optimized representations of causal histories, which are easy to understand. By building on the notion of causal histories, users can begin to see the logic ehind these mechanisms, to identify how they differ, and even consider possible optimizations. When confronted with an unfamiliar causality tracking mechanism, or when trying to design a new system that requires it, readers should ask two simple questions, which events need tracking and how does the mechanism translate back to a simple causal history.