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new 9f2e2f2 ZOOKEEPER-3537: Leader election - Use of out of election
messages
9f2e2f2 is described below
commit 9f2e2f238c4bcbb0170bb6a983ffa4e92f701488
Author: Karolos Antoniadis <karo...@gmail.com>
AuthorDate: Mon Sep 30 14:22:31 2019 -0700
ZOOKEEPER-3537: Leader election - Use of out of election messages
Just a small change. Check leader in `recvset` when consider notifications
from the same election, and not from `outofelection`.
Parameter `n.state` is needed when creating the new `Vote` because
otherwise the vote will be in a `LOOKING` state and hence `checkLeader` will
fail when checking whether the leader is
[`LEADING`](https://github.com/apache/zookeeper/blob/master/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/FastLeaderElection.java#L793).
Author: Karolos Antoniadis <karo...@gmail.com>
Reviewers: Allan Lyu <fang...@apache.org>, Michael Han <h...@apache.org>
Closes #1081 from insumity/ZOOKEEPER-3537
---
.../zookeeper/server/quorum/FastLeaderElection.java | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git
a/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/FastLeaderElection.java
b/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/FastLeaderElection.java
index 4e010b7..b3657da 100644
---
a/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/FastLeaderElection.java
+++
b/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/FastLeaderElection.java
@@ -907,8 +907,20 @@ public class FastLeaderElection implements Election {
self.start_fle = Time.currentElapsedTime();
try {
+ /*
+ * The votes from the current leader election are stored in
recvset. In other words, a vote v is in recvset
+ * if v.electionEpoch == logicalclock. The current participant
uses recvset to deduce on whether a majority
+ * of participants has voted for it.
+ */
Map<Long, Vote> recvset = new HashMap<Long, Vote>();
+ /*
+ * The votes from previous leader elections, as well as the votes
from the current leader election are
+ * stored in outofelection. Note that notifications in a LOOKING
state are not stored in outofelection.
+ * Only FOLLOWING or LEADING notifications are stored in
outofelection. The current participant could use
+ * outofelection to learn which participant is the leader if it
arrives late (i.e., higher logicalclock than
+ * the electionEpoch of the received notifications) in a leader
election.
+ */
Map<Long, Vote> outofelection = new HashMap<Long, Vote>();
int notTimeout = minNotificationInterval;
@@ -1032,9 +1044,9 @@ public class FastLeaderElection implements Election {
* together.
*/
if (n.electionEpoch == logicalclock.get()) {
- recvset.put(n.sid, new Vote(n.leader, n.zxid,
n.electionEpoch, n.peerEpoch));
+ recvset.put(n.sid, new Vote(n.leader, n.zxid,
n.electionEpoch, n.peerEpoch, n.state));
voteSet = getVoteTracker(recvset, new
Vote(n.version, n.leader, n.zxid, n.electionEpoch, n.peerEpoch, n.state));
- if (voteSet.hasAllQuorums() &&
checkLeader(outofelection, n.leader, n.electionEpoch)) {
+ if (voteSet.hasAllQuorums() &&
checkLeader(recvset, n.leader, n.electionEpoch)) {
setPeerState(n.leader, voteSet);
Vote endVote = new Vote(n.leader, n.zxid,
n.electionEpoch, n.peerEpoch);
leaveInstance(endVote);
@@ -1045,6 +1057,9 @@ public class FastLeaderElection implements Election {
/*
* Before joining an established ensemble, verify that
* a majority are following the same leader.
+ *
+ * Note that the outofelection map also stores votes
from the current leader election.
+ * See ZOOKEEPER-1732 for more information.
*/
outofelection.put(n.sid, new Vote(n.version, n.leader,
n.zxid, n.electionEpoch, n.peerEpoch, n.state));
voteSet = getVoteTracker(outofelection, new
Vote(n.version, n.leader, n.zxid, n.electionEpoch, n.peerEpoch, n.state));
