xyuanlu commented on code in PR #2562:
URL: https://github.com/apache/helix/pull/2562#discussion_r1269030338
##########
meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java:
##########
@@ -136,27 +139,63 @@ public void joinLeaderElectionParticipantPool(String
leaderPath) {
public void joinLeaderElectionParticipantPool(String leaderPath, LeaderInfo
userInfo) {
// TODO: create participant entry with info
subscribeAndTryCreateLeaderEntry(leaderPath);
+
+ LeaderInfo participantInfo = new LeaderInfo(userInfo);
+ createParticipantInfo(leaderPath, participantInfo);
+ }
+
+ private void createParticipantInfo(String leaderPath, LeaderInfo
participantInfo) {
+
+ try {
+ // try to create participant info entry, assuming leader election group
node is already there
+ _metaClient.create(leaderPath + PARTICIPANTS_ENTRY_PARENT +
_participant, participantInfo,
+ MetaClientInterface.EntryMode.EPHEMERAL);
+ } catch (MetaClientNodeExistsException ex) {
+ LOG.info("Already joined pool {}.", leaderPath);
+ return;
+ } catch (MetaClientNoNodeException ex) {
+ try {
+ try {
+ // try to create participants root entry. This function is called
after
+ // `subscribeAndTryCreateLeaderEntry`, so leader election root node
should have already been created.
+ LOG.info("{} Creating leader group directory {}.", _participant,
leaderPath);
+ _metaClient.create(leaderPath + PARTICIPANTS_ENTRY_KEY, null);
+ } catch (MetaClientNodeExistsException ignored) {
+ // participants' root entry created by other client, ignore
+ }
+ // try to participant info node again.
+ _metaClient.create(leaderPath + PARTICIPANTS_ENTRY_PARENT +
_participant, participantInfo,
+ MetaClientInterface.EntryMode.EPHEMERAL);
+ } catch (MetaClientNoNodeException e) {
+ // catch exception in previous 2 create()
+ // Leader group root entry or participant parent entry is gone after
we checked or created.
+ // Meaning other client removed the group. Throw
ConcurrentModificationException.
+ throw new ConcurrentModificationException(
+ "Other client trying to modify the leader election group at the
same time, please retry.", ex);
+ }
+ }
}
private void subscribeAndTryCreateLeaderEntry(String leaderPath) {
_metaClient.subscribeDataChange(leaderPath + LEADER_ENTRY_KEY,
_reElectListener, false);
- LeaderInfo leaderInfo = new LeaderInfo(LEADER_ENTRY_KEY);
+ LeaderInfo leaderInfo = new LeaderInfo("LEADER");
Review Comment:
Missed it. It was a mistaken resolved conflict. (was changing from "LEADER"
to using static string)
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