Log Structure 1 2 3 4 5 6 7 8 log index term leader Server 1 command y = 1 1 y = 9 2 x = 2 3 z = 0 3 y = 7 3 x = 5 3 z = 3 term leader Server 1 command 1 x = 3 1 y = 1 1 y = 9 2 x = 2 3 z = 0 Server 2 1 x = 3 1 y = 1 1 y = 9 2 x = 2 3 z = 0 3 y = 7 3 x = 5 3 z = 3 Server 3 followers 1 x = 3 1 y = 1 Server 4 1 x = 3 1 y = 1 1 y = 9 2 x = 2 3 z = 0 3 y = 7 3 x = 5 Server 5 committed entries CS 190 Lecture Notes: Raft

Log Inconsistencies term 1 1 1 4 4 5 5 6 6 6 Server 1 2 3 4 5 6 7 8 9 10 11 12 1 1 1 4 4 5 5 6 6 6 Server 1 leader for term 8 1 1 1 4 4 5 5 6 6 Server 2 1 1 1 4 Server 3 1 1 1 4 4 5 5 6 6 6 6 Server 4 followers 1 1 1 4 4 5 5 6 6 6 7 7 Server 5 1 1 1 4 4 4 4 Server 6 1 1 1 2 2 2 3 3 3 3 3 Server 7 CS 190 Lecture Notes: Raft

When Is It Safe To Commit? leader 1 2 1 2 1 2 3 1 2 1 2 3 1 2 1 2 1 2 4 1 3 1 2 4 S1 1 2 1 2 1 2 1 3 1 2 4 S2 1 1 1 2 1 3 1 2 4 S3 S4 1 1 1 1 3 1 1 1 3 1 3 1 3 1 3 S5 Term 2 Term 3 Term 4 Term 5 Term 4’ CS 190 Lecture Notes: Raft