Cluster Controls

A raft cluster may be controlled in various ways using the API methods of the Raft type. This allows the application to influence the raft behavior.

There are several concepts related to cluster control:

• Voter: a raft node that is responsible to vote, elect itself for leadership(Candidate), become Leader or Follower

• Candidate: a node tries to elect itself as the Leader.

• Leader: the only node in a cluster that deals with application request.

• Follower: a node that believes there is a legal leader and just receives replicated logs.

• Learner: a node that is not allow to vote but only receives logs.

Voter state transition:

                         vote granted by a quorum
          .--> Candidate ----------------------> Leader
heartbeat |     |                                  |
timeout   |     | seen a higher Leader             | seen a higher Leader
          |     v                                  |
          '----Follower <--------------------------'