Lesson 3: Time in Distributed Systems Flashcards
What is physical time? How is it different than logical time?
Physical Time is the time on an actual clock.
Logical Time keeps track of time in their own way, but they can be used to order events in a distributed system.
Why do we need time?
When we’re working with a single node it’s easy for us to determine the order of events based on timestamp.
Order is a requirement for:
- causality
- scheduling
- garbage collection
Why is measuring time hard in distributed systems?
Network delays and lost messages make it impossible for the receiver of events to make any guarantees about the order of events.
We could have each node timestamp its message and then order on the receiving node based on these timestamps. However, clocks are not guaranteed to be synchronized!
