private boolean updateFollowerLogInformation(
FollowerLogInformation followerLogInformation, AppendEntriesReply appendEntriesReply) {
boolean updated = followerLogInformation.setMatchIndex(appendEntriesReply.getLogLastIndex());
updated =
followerLogInformation.setNextIndex(appendEntriesReply.getLogLastIndex() + 1) || updated;
if (updated && LOG.isDebugEnabled()) {
LOG.debug(
"{}: handleAppendEntriesReply - FollowerLogInformation for {} updated: matchIndex: {}, nextIndex: {}",
logName(),
followerLogInformation.getId(),
followerLogInformation.getMatchIndex(),
followerLogInformation.getNextIndex());
}
return updated;
}
@Override
protected RaftActorBehavior handleAppendEntriesReply(
ActorRef sender, AppendEntriesReply appendEntriesReply) {
if (LOG.isTraceEnabled()) {
LOG.trace("{}: handleAppendEntriesReply: {}", logName(), appendEntriesReply);
}
// Update the FollowerLogInformation
String followerId = appendEntriesReply.getFollowerId();
FollowerLogInformation followerLogInformation = followerToLog.get(followerId);
if (followerLogInformation == null) {
LOG.error("{}: handleAppendEntriesReply - unknown follower {}", logName(), followerId);
return this;
}
if (followerLogInformation.timeSinceLastActivity()
> context.getConfigParams().getElectionTimeOutInterval().toMillis()) {
LOG.warn(
"{} : handleAppendEntriesReply delayed beyond election timeout, "
+ "appendEntriesReply : {}, timeSinceLastActivity : {}, lastApplied : {}, commitIndex : {}",
logName(),
appendEntriesReply,
followerLogInformation.timeSinceLastActivity(),
context.getLastApplied(),
context.getCommitIndex());
}
followerLogInformation.markFollowerActive();
followerLogInformation.setPayloadVersion(appendEntriesReply.getPayloadVersion());
boolean updated = false;
if (appendEntriesReply.isSuccess()) {
updated = updateFollowerLogInformation(followerLogInformation, appendEntriesReply);
} else {
LOG.debug(
"{}: handleAppendEntriesReply: received unsuccessful reply: {}",
logName(),
appendEntriesReply);
long followerLastLogIndex = appendEntriesReply.getLogLastIndex();
ReplicatedLogEntry followersLastLogEntry =
context.getReplicatedLog().get(followerLastLogIndex);
if (appendEntriesReply.isForceInstallSnapshot()) {
// Reset the followers match and next index. This is to signal that this follower has
// nothing
// in common with this Leader and so would require a snapshot to be installed
followerLogInformation.setMatchIndex(-1);
followerLogInformation.setNextIndex(-1);
// Force initiate a snapshot capture
initiateCaptureSnapshot(followerId);
} else if (followerLastLogIndex < 0
|| (followersLastLogEntry != null
&& followersLastLogEntry.getTerm() == appendEntriesReply.getLogLastTerm())) {
// The follower's log is empty or the last entry is present in the leader's journal
// and the terms match so the follower is just behind the leader's journal from
// the last snapshot, if any. We'll catch up the follower quickly by starting at the
// follower's last log index.
updated = updateFollowerLogInformation(followerLogInformation, appendEntriesReply);
} else {
// TODO: When we find that the follower is out of sync with the
// Leader we simply decrement that followers next index by 1.
// Would it be possible to do better than this? The RAFT spec
// does not explicitly deal with it but may be something for us to
// think about.
followerLogInformation.decrNextIndex();
}
}
// Now figure out if this reply warrants a change in the commitIndex
// If there exists an N such that N > commitIndex, a majority
// of matchIndex[i] ≥ N, and log[N].term == currentTerm:
// set commitIndex = N (§5.3, §5.4).
for (long N = context.getCommitIndex() + 1; ; N++) {
int replicatedCount = 1;
for (FollowerLogInformation info : followerToLog.values()) {
if (info.getMatchIndex() >= N) {
replicatedCount++;
}
}
if (replicatedCount >= minReplicationCount) {
ReplicatedLogEntry replicatedLogEntry = context.getReplicatedLog().get(N);
if (replicatedLogEntry != null && replicatedLogEntry.getTerm() == currentTerm()) {
context.setCommitIndex(N);
} else {
break;
}
} else {
break;
}
}
// Apply the change to the state machine
if (context.getCommitIndex() > context.getLastApplied()) {
if (LOG.isDebugEnabled()) {
LOG.debug(
"{}: handleAppendEntriesReply from {}: applying to log - commitIndex: {}, lastAppliedIndex: {}",
logName(),
followerId,
context.getCommitIndex(),
context.getLastApplied());
}
applyLogToStateMachine(context.getCommitIndex());
}
if (!context.getSnapshotManager().isCapturing()) {
purgeInMemoryLog();
}
// Send the next log entry immediately, if possible, no need to wait for heartbeat to trigger
// that event
sendUpdatesToFollower(followerId, followerLogInformation, false, !updated);
return this;
}