szetszwo commented on a change in pull request #184:
URL: https://github.com/apache/incubator-ratis/pull/184#discussion_r479615443
##########
File path:
ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderState.java
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@@ -794,12 +795,58 @@ private void replicateNewConf() {
return lists;
}
+ private void yieldLeaderToHigherPriorityPeer() {
+ if (!server.getRole().isLeader()) {
+ return;
+ }
+
+ final RaftConfiguration conf = server.getRaftConf();
+ int leaderPriority = conf.getPeer(server.getId()).getPriority();
+
+ TermIndex leaderLastEntry = server.getState().getLastEntry();
+
+ for (LogAppender logAppender : senders.getSenders()) {
+ FollowerInfo followerInfo = logAppender.getFollower();
+ RaftPeerId followerID = followerInfo.getPeer().getId();
+ int followerPriority = conf.getPeer(followerID).getPriority();
+
+ if (followerPriority <= leaderPriority) {
+ continue;
+ }
+
+ if (leaderLastEntry == null) {
+ LOG.info("{} stepDown leadership on term:{} because follower's
priority:{} is higher than leader's:{} " +
+ "and leader's lastEntry is null",
+ this, currentTerm, followerPriority, leaderPriority);
+
+ // step down as follower
+ stepDown(currentTerm);
+ return;
+ }
+
+ if (followerInfo.getMatchIndex() >= leaderLastEntry.getIndex()) {
+ LOG.info("{} stepDown leadership on term:{} because follower's
priority:{} is higher than leader's:{} " +
+ "and follower's lastEntry index:{} catch up with leader's:{}",
+ this, currentTerm, followerPriority, leaderPriority,
followerInfo.getMatchIndex(),
+ leaderLastEntry.getIndex());
+
+ // step down as follower
+ stepDown(currentTerm);
Review comment:
There may be a race condition -- when stepping down, the lastEntry may
change since the code is not synchronized. However, "synchronized" is not a
good idea since it will slow down the leader.
How about we add a new method, say stepDown(lastEntry), which is
synchronized and also check if the given lastEntry matched the log's last entry?
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