truetime

Tags: clocks (distributed systems), cloud

https://cloud.google.com/spanner/docs/true-time-external-consistency

• HA distributed clock service, similar to NTP

• True time provides an interval of time, and a way to tell if things were bfeore and after

  • TT.now() -> TTinterval: [earliest, latest]
  • TT.after(t) -> True if t has definitely passed
  • TT.before(t) -> True if t has definitely not arrived

• TrueTime error comes from round trip time to the clock server, clock drift, and time to sycnronize wit hother clocks

  

• truetime effectively allows us to do what vector clocks do but with much less space

• Gives Spanner it’s external consistency (linearizability).