kaijchen commented on code in PR #845:
URL: https://github.com/apache/ratis/pull/845#discussion_r1138087986
##########
ratis-server/src/main/java/org/apache/ratis/server/impl/TransferLeadership.java:
##########
@@ -93,49 +132,76 @@ boolean isSteppingDown() {
}
void onFollowerAppendEntriesReply(LeaderStateImpl leaderState, FollowerInfo
follower) {
- final Optional<RaftPeerId> transferee = getTransferee();
// If the transferee has just append some entries and becomes up-to-date,
// send StartLeaderElection to it
- if (transferee.filter(t -> t.equals(follower.getId())).isPresent()
- && leaderState.sendStartLeaderElection(follower)) {
- LOG.info("{}: sent StartLeaderElection to transferee {} after received
AppendEntriesResponse",
- server.getMemberId(), transferee.get());
+ if (getTransferee().filter(t -> t.equals(follower.getId())).isPresent()) {
+ final String error = leaderState.sendStartLeaderElection(follower,
leaderState.getLastEntry());
+ if (error == null) {
+ LOG.info("{}: sent StartLeaderElection to transferee {} after received
AppendEntriesResponse",
+ server.getMemberId(), follower.getId());
+ }
}
}
- private void tryTransferLeadership(LeaderStateImpl leaderState, RaftPeerId
transferee) {
+ private String tryTransferLeadership(LeaderStateImpl leaderState, Context
context) {
+ final RaftPeerId transferee = context.getTransfereeId();
LOG.info("{}: start transferring leadership to {}", server.getMemberId(),
transferee);
- final LogAppender appender =
leaderState.getLogAppender(transferee).orElse(null);
-
+ final LogAppender appender = context.getTransfereeLogAppender();
if (appender == null) {
- LOG.error("{}: cannot find LogAppender for transferee {}",
server.getMemberId(), transferee);
- return;
+ return "LogAppender for transferee " + transferee + " is null";
}
final FollowerInfo follower = appender.getFollower();
- if (leaderState.sendStartLeaderElection(follower)) {
+ final String error = leaderState.sendStartLeaderElection(follower,
context.getLeaderLastEntry());
+ if (error == null) {
LOG.info("{}: sent StartLeaderElection to transferee {} immediately as
it already has up-to-date log",
server.getMemberId(), transferee);
- } else {
- LOG.info("{}: notifying LogAppender to send AppendEntries as transferee
{} is not up-to-date",
- server.getMemberId(), transferee);
+ } else if (error.contains("not up-to-date")) {
+ LOG.info("{}: notifying LogAppender to send AppendEntries as transferee
{} is not up-to-date: {}",
+ server.getMemberId(), transferee, error);
appender.notifyLogAppender();
+ return null;
}
+ return error;
+ }
+
+ TransferLeadershipRequest newRequest(RaftPeerId transfereeId) {
+ // TransferLeadership will block client request, so we don't want wait too
long.
+ // If everything goes well, transferee should be elected within an
election timeout.
+ final long timeout =
server.getRandomElectionTimeout().toLong(TimeUnit.MILLISECONDS);
Review Comment:
Does it mean, it is possible for a follower to start election as soon as an
appendEntries times out?
Should we seperate these two timeouts (in the future)?
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