distributed-systemraft

Why current term in raft consensus algorithm must be monotonic

I am watching MIT 6.824 courses (47'23'' inside https://www.youtube.com/watch?v=h3JiQ_lnkE8)

Prof mentioned current term needs to be persistent in disk, because current term must be monotonic. Why current term in raft consensus algorithm must be monotonic? If not, what will happen?

Solution

  • Aren't they talk about log being persistent? Since every log entry has a term associated with it, the term is persistent as well.

    As for monotonic term, it has to be increasing with each next round so participants could detect and reject messages from older leaders (if a leader freeze, new one being elected and old one comes back to life).