Lamport: Time Clock and the Ordering of Distributed Systems

Tags: papers, computers

• https://lamport.azurewebsites.net/pubs/time-clocks.pdf

• Uses “happens before” - partial ordering of events

  • Introduces a way to sync the total ordering
  • provides for clocks, how to translate it to actual clocks

• is time subjective? is it independent of observers?

• is there a way to capture “happen before” without clocks?

  • can we determine if a single event preceded another without the measurement of objective time?
  • on differing nodes
  • total ordering of events cannot be done, only partial ordering on specific nodes
    • 1: a-b-c
    • 2: x-y-z
    • a comes before b and c, but a does not come before x, y, or z

• “happens before”

  • a and b are in the same process, and a comes before b, a happens before b
  • if a sends a message and b receives it, a must happen before b
  • if a -> t and t -> b then a -> b
    • transitivity