return returnBehavior;
}
+ /**
+ * Attempts to transfer leadership to a follower as per the raft paper (ยง3.10) as follows:
+ * <ul>
+ * <li>Start a timer (Stopwatch).</li>
+ * <li>Send an initial AppendEntries heartbeat to all followers.</li>
+ * <li>On AppendEntriesReply, check if the follower's new match Index matches the leader's last index</li>
+ * <li>If it matches, </li>
+ * <ul>
+ * <li>Send an additional AppendEntries to ensure the follower has applied all its log entries to its state.</li>
+ * <li>Send an ElectionTimeout to the follower to immediately start an election.</li>
+ * <li>Notify {@link RaftActorLeadershipTransferCohort#transferComplete}.</li>
+ * </ul>
+ * <li>Otherwise if the election time out period elapses, notify
+ * {@link RaftActorLeadershipTransferCohort#abortTtransfer}.</li>
+ * </ul>
+ *
+ * @param leadershipTransferCohort
+ */
public void transferLeadership(@Nonnull RaftActorLeadershipTransferCohort leadershipTransferCohort) {
- if(!context.hasFollowers()) {
- leadershipTransferCohort.transferComplete();
- return;
- }
-
LOG.debug("{}: Attempting to transfer leadership", logName());
leadershipTransferContext = new LeadershipTransferContext(leadershipTransferCohort);
}
long lastIndex = context.getReplicatedLog().lastIndex();
+ boolean isVoting = context.getPeerInfo(followerId).isVoting();
- LOG.debug("{}: tryToCompleteLeadershipTransfer: followerId: {}, matchIndex: {}, lastIndex: {}",
- logName(), followerId, followerInfo.getMatchIndex(), lastIndex);
+ LOG.debug("{}: tryToCompleteLeadershipTransfer: followerId: {}, matchIndex: {}, lastIndex: {}, isVoting: {}",
+ logName(), followerId, followerInfo.getMatchIndex(), lastIndex, isVoting);
- if(followerInfo.getMatchIndex() == lastIndex) {
+ if(isVoting && followerInfo.getMatchIndex() == lastIndex) {
LOG.debug("{}: Follower's log matches - sending ElectionTimeout", logName());
// We can't be sure if the follower has applied all its log entries to its state so send an
- // additional AppendEntries.
+ // additional AppendEntries with the latest commit index.
sendAppendEntries(0, false);
// Now send an ElectionTimeout to the matching follower to immediately start an election.