MakeProgressTracker initializes a ProgressTracker.

NewInflights sets up an Inflights that allows up to 'size' inflight messages.

StateProbe indicates a follower whose last index isn't known.

StateReplicate is the state steady in which a follower eagerly receives log entries to append to its log.

StateSnapshot indicates a follower that needs log entries not available from the leader's Raft log.

Config reflects the configuration tracked in a ProgressTracker.

Inflights limits the number of MsgApp (represented by the largest index contained within) sent to followers but not yet acknowledged by them.

Progress represents a follower’s progress in the view of the leader.

ProgressTracker tracks the currently active configuration and the information known about the nodes and learners in it.

ProgressMap is a map of *Progress.

StateType is the state of a tracked follower.