pkuwm commented on a change in pull request #1066:
URL: https://github.com/apache/helix/pull/1066#discussion_r462523745
##########
File path: helix-core/src/main/java/org/apache/helix/model/Message.java
##########
@@ -953,4 +970,35 @@ public boolean isValid() {
}
return true;
}
+
+ // A class represents session aware ZNRecord for message. The message should
be written to zk
+ // by the expected session.
+ // TODO: remove this class once public session-aware ZNRecord is available
+ private static class SessionAwareZNRecord extends ZNRecord implements
SessionAwareZkWriteData {
Review comment:
@lei-xia I've considered and tried to break the PR down to 2 smaller
ones: fixing the issue without new interface and adding new interface. But the
first one PR would look quite hacky and I don't feel comfortable merging the
commit to code base. So I decided to keep this PR and make
`SessionAwareZNRecord` public. Even in the future we need to add more APIs to
the interface, we could also add API implementation to `SessionAwareZNRecord`.
In this way, I feel it is cleaner to check in.
##########
File path: helix-core/src/main/java/org/apache/helix/HelixManager.java
##########
@@ -419,6 +420,17 @@ void
addExternalViewChangeListener(org.apache.helix.ExternalViewChangeListener l
*/
Long getSessionStartTime();
+ /**
+ * Checks whether the cluster manager is leader and returns the session ID
associated to the
+ * connection of cluster data store, if and only if it is leader.
+ *
+ * @return {@code Optional<String>} session ID is present inside the {@code
Optional} object
+ * if the cluster manager is leader. Otherwise, returns an empty {@code
Optional} object.
+ */
+ default Optional<String> getSessionIdIfLead() {
Review comment:
One more thing for `why do we need this if we already have
manager.getSessionId?`:
`getSessionId` just directly returns the existing sessionId in manager. But
`getSessionIdIfLeader()` does more thing by reading zk to check leadership.
This is the main difference.
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