GlenGeng commented on a change in pull request #150:
URL: https://github.com/apache/incubator-ratis/pull/150#discussion_r462238086
##########
File path:
ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderState.java
##########
@@ -792,6 +794,47 @@ private void replicateNewConf() {
return lists;
}
+ /**
+ * See the thesis section 6.2: A leader in Raft steps down
+ * if an election timeout elapses without a successful
+ * round of heartbeats to a majority of its cluster.
+ */
+ private void checkLeadership() {
+ // The initial value of lastRpcResponseTime in FollowerInfo is set by
+ // LeaderState::addSenders(), which is fake and used to trigger an
+ // immediate round of AppendEntries request. Since candidates collect
+ // votes from majority before becoming leader, without seeing higher term,
+ // ideally, A leader is legal for election timeout if become leader soon.
+ if (server.getRole().getRoleElapsedTimeMs() < server.getMaxTimeoutMs()) {
+ return;
+ }
+
+ final List<RaftPeerId> activePeers = senders.stream()
+ .filter(sender -> sender.getFollower()
+ .getLastRpcResponseTime()
+ .elapsedTimeMs() <= server.getMaxTimeoutMs())
+ .map(sender -> sender.getFollower().getPeer().getId())
+ .collect(Collectors.toList());
+
+ final RaftConfiguration conf = server.getRaftConf();
+
+ if (conf.hasMajority(activePeers, server.getId())) {
+ // leadership check passed
+ return;
+ }
+
+ List<FollowerInfo> followers = senders.stream()
+ .map(LogAppender::getFollower).collect(Collectors.toList());
+
+ LOG.warn(this + ": Lost leadership on term: " + currentTerm
+ + ". Election timeout: " + server.getMaxTimeoutMs() + "ms"
+ + ". In charge for: " + server.getRole().getRoleElapsedTimeMs() + "ms"
+ + ". Conf: " + conf + ". Followers: " + followers);
+
+ // become follower of next term.
+ stepDown(currentTerm + 1);
Review comment:
ok
##########
File path: ratis-server/src/test/java/org/apache/ratis/RaftAsyncTests.java
##########
@@ -402,6 +407,46 @@ void runTestAppendEntriesTimeout(CLUSTER cluster) throws
Exception {
RaftServerConfigKeys.RetryCache.setExpiryTime(getProperties(),
oldExpiryTime);
}
+ @Test
+ public void testCheckLeadershipFailure() throws Exception {
+ runWithNewCluster(NUM_SERVERS, this::runTestCheckLeadershipFailure);
+ }
+
+ void runTestCheckLeadershipFailure(CLUSTER cluster) throws Exception {
Review comment:
"This test can also pass when followers turn to candidate state and
trigger an election."
We don't need to worry about this, the `outstandingOp` will prevent follower
to timeout.
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