Safety

Once a log entry has been applied to a state machine, no other state machine must apply a different value for that log entry.

Raft safety property

• If a leader has decided that a log entry is committed, that entry will be present in the logs of all future leaders

This guarantees the safety requirement

• Leaders never overwrite entries in their logs

• Only entries in the leader’s log can be committed

• Entries must be committed before applying to state machine