kaijchen commented on code in PR #845:
URL: https://github.com/apache/ratis/pull/845#discussion_r1140975322
##########
ratis-server/src/main/java/org/apache/ratis/server/impl/TransferLeadership.java:
##########
@@ -92,50 +188,135 @@ boolean isSteppingDown() {
return pending.get() != null;
}
+ static Result isFollowerUpToDate(FollowerInfo follower, TermIndex
leaderLastEntry) {
+ if (follower == null) {
+ return Result.NULL_FOLLOWER;
+ } else if (leaderLastEntry != null) {
+ final long followerMatchIndex = follower.getMatchIndex();
+ if (followerMatchIndex < leaderLastEntry.getIndex()) {
+ return new Result(Result.Type.NOT_UP_TO_DATE, "followerMatchIndex = "
+ followerMatchIndex
+ + " < leaderLastEntry.getIndex() = " + leaderLastEntry.getIndex());
+ }
+ }
+ return Result.SUCCESS;
+ }
+
+ private Result sendStartLeaderElection(FollowerInfo follower, TermIndex
lastEntry) {
+ final Result result = isFollowerUpToDate(follower, lastEntry);
+ if (result != Result.SUCCESS) {
+ return result;
+ }
+
+ final TermIndex currLastEntry = server.getState().getLastEntry();
+ if (ServerState.compareLog(currLastEntry, lastEntry) != 0) {
+ return new Result(Result.Type.LAST_ENTRY_CHANGED,
Review Comment:
I'm wondering why we should abort TransferLeadership when
`LAST_ENTRY_CHANGED`.
The `StartLeaderElection` request shoud be idempotent (by including sender's
term).
Then, as long as follower is up-to-date, it is OK to send the request.
i.e. Only check `isFollowerUpToDate(follower, currLastEntry)`.
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