Leader Failover — Promoting a Follower, Fencing the Old Leader

Leader Failover — Promoting a Follower, Fencing the Old Leader A sequence diagram generated by Archify. write request replicate, wait for ack replicate, no waiting write request — no response failure detected only by timeout elect the most up-to-date follower consensus problem — Chapter 10 I am the new leader — send writes here old leader rejoins the cluster may still believe it is leader step down — fencing rejects your writes unreplicated writes are discarded Normal operation Leader failure and failover Old leader rejoins Client · Sequence participant Client Leader (old) · crashes mid-write · Sequence participant Leader (old) crashes mid-write Follower 1 · most up-to-date · Sequence participant Follower 1 most up-to-date Follower 2 · falling behind · Sequence participant Follower 2 falling behind Legend main request return async trace message