jiajunwang commented on a change in pull request #642: Fix handleNewSession
creating ephemeral node with expired session
URL: https://github.com/apache/helix/pull/642#discussion_r364004887
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File path:
helix-core/src/main/java/org/apache/helix/manager/zk/ZKHelixManager.java
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@@ -1134,9 +1159,31 @@ public void handleNewSession(final String sessionId)
throws Exception {
// Wait until we get a non-zero session id. Otherwise, getSessionId()
might be null.
waitUntilConnected();
- // TODO: filter out stale sessions here.
+ /*
+ * Filter out stale sessions. If a session id is not null and not the same
as current session
+ * id, this session is expired. With this filtering, expired sessions are
NOT handled,
+ * so performance is expected to improve.
+ */
+ if (sessionId != null && !getSessionId().equals(sessionId)) {
+ LOG.info("Session is expired and not handled. Expected: {}. Actual:
{}.", sessionId,
+ getSessionId());
+ return;
+ }
+
+ /*
+ * When a null session id is passed in, we will take current session's id
for following
+ * operations. Please note that current session might not be the one we
expect to handle,
+ * because the one we expect might be already expired when the zk event is
waiting in the
+ * event queue. Why we use current session here is for backward
compatibility with the old
+ * method handleNewSession().
+ */
+ if (sessionId == null) {
+ sessionId = getSessionId();
+ LOG.warn("Session id: <null> is passed in. Current session id: {} will
be used.", sessionId);
Review comment:
nit, LOG.debug?
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