LB-Yu commented on code in PR #1401:
URL: https://github.com/apache/fluss/pull/1401#discussion_r2281474715
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fluss-server/src/main/java/com/alibaba/fluss/server/coordinator/CoordinatorServer.java:
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@@ -157,10 +158,45 @@ public static void main(String[] args) {
@Override
protected void startServices() throws Exception {
+ electCoordinatorLeader();
+ }
+
+ private void electCoordinatorLeader() throws Exception {
+ this.zkClient = ZooKeeperUtils.startZookeeperClient(conf, this);
+
+ // Coordinator Server supports high availability. If 3 coordinator
servers are alive,
+ // one of them will be elected as leader and the other two will be
standby.
+ // When leader fails, one of standby coordinators will be elected as
new leader.
+ // All of them register to ZK like tablet servers in path
+ // "/coordinators/ids/1","/coordinators/ids/2","/coordinators/ids/3".
+ // but the leader will be elected in path "/coordinators/leader"
additionally.
+ registerCoordinatorServer();
+ ZooKeeperUtils.registerZookeeperClientReInitSessionListener(
+ zkClient, this::registerCoordinatorServer, this);
+
+ // try to register Coordinator leader once
+ if (tryElectCoordinatorLeaderOnce()) {
+ startCoordinatorLeaderService();
+ } else {
+ // standby
+ CoordinatorLeaderElection coordinatorLeaderElection =
+ new CoordinatorLeaderElection(zkClient.getCuratorClient(),
serverId);
+ coordinatorLeaderElection.startElectLeader(
+ () -> {
+ try {
+ startCoordinatorLeaderService();
+ } catch (Exception e) {
+ throw new RuntimeException(e);
+ }
+ });
+ }
Review Comment:
This logic looks strange to me. Why do we explicitly create the path for the
first election, but use `LeaderLatch` for the standby Coordinator? Since we’re
already using the framework, perhaps we could standardize on `LeaderLatch`?
Also, this logic seems problematic. If cs-1 becomes the leader on the first
startup and later loses leadership due to a network issue, it appears it will
never participate in the election again, because no `LeaderLatch` was
registered for the node that became leader during the first startup.
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