Clocks & Ordering

Time, Clocks, and the Ordering of Events in a Distributed System

Leslie Lamport

Defines happened-before and logical clocks, giving distributed systems a usable notion of order without shared time.

Assumes partial orders, and accepting that a shared "now" is not available; the rest is built in the paper

Virtual Time and Global States of Distributed Systems

Friedemann Mattern

Generalises Lamport's logical clocks into vector clocks, giving processes a way to determine precisely which events could and could not have influenced each other.

Logical Physical Clocks and Consistent Snapshots in Globally Distributed Databases

Sandeep S. Kulkarni et al.

Combines physical and logical clocks so causality tracking gets the compactness of physical timestamps without losing Lamport's ordering guarantee.