raft.go
func (r *Raft) checkLeaderLease() time.Duration {
	// Track contacted nodes, we can always contact ourself
	contacted := 1

	// Check each follower
	var maxDiff time.Duration
	now := time.Now()
	for peer, f := range r.leaderState.replState {
		diff := now.Sub(f.LastContact())
		if diff <= r.conf.LeaderLeaseTimeout {
			contacted++
			if diff > maxDiff {
				maxDiff = diff
			}
		} else {
			// Log at least once at high value, then debug. Otherwise it gets very verbose.
			if diff <= 3*r.conf.LeaderLeaseTimeout {
				r.logger.Warn(fmt.Sprintf("Failed to contact %v in %v", peer, diff))
			} else {
				r.logger.Debug(fmt.Sprintf("Failed to contact %v in %v", peer, diff))
			}
		}
		metrics.AddSample([]string{"raft", "leader", "lastContact"}, float32(diff/time.Millisecond))
	}

	// Verify we can contact a quorum
	quorum := r.quorumSize()
	if contacted < quorum {
		r.logger.Warn("Failed to contact quorum of nodes, stepping down")
		r.setState(Follower)
		metrics.IncrCounter([]string{"raft", "transition", "leader_lease_timeout"}, 1)
	}
	return maxDiff
}
func (r *Raft) checkLeaderLease() time.Duration {
	// Track contacted nodes, we can always contact ourself
	contacted := 1

	// Check each follower
	var maxDiff time.Duration
	now := time.Now()
	for peer, f := range r.leaderState.replState {
		diff := now.Sub(f.LastContact())
		if diff <= r.conf.LeaderLeaseTimeout {
			contacted++
			if diff > maxDiff {
				maxDiff = diff
			}
		} else {
			// Log at least once at high value, then debug. Otherwise it gets very verbose.
			if diff <= 3*r.conf.LeaderLeaseTimeout {
				r.logger.Warn(fmt.Sprintf("Failed to contact %v in %v", peer, diff))
			} else {
				r.logger.Debug(fmt.Sprintf("Failed to contact %v in %v", peer, diff))
			}
		}
		metrics.AddSample([]string{"raft", "leader", "lastContact"}, float32(diff/time.Millisecond))
	}

	// Verify we can contact a quorum
	quorum := r.quorumSize()
	if contacted < quorum {
		r.logger.Warn("Failed to contact quorum of nodes, stepping down")
		r.setState(Follower)
		metrics.IncrCounter([]string{"raft", "transition", "leader_lease_timeout"}, 1)
	}
	return maxDiff
}
// checkLeaderLease is used to check if we can contact a quorum of nodes
// within the last leader lease interval. If not, we need to step down,
// as we may have lost connectivity. Returns the maximum duration without
// contact. This must only be called from the main thread.