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https://issues.apache.org/jira/browse/ZOOKEEPER-2926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16322343#comment-16322343
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ASF GitHub Bot commented on ZOOKEEPER-2926:
-------------------------------------------
Github user anmolnar commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/447#discussion_r160976160
--- Diff:
src/java/main/org/apache/zookeeper/server/quorum/LearnerSessionTracker.java ---
@@ -102,32 +101,42 @@ public boolean isGlobalSession(long sessionId) {
}
public boolean addGlobalSession(long sessionId, int sessionTimeout) {
+ // no global session tracker, do nothing
+ return false;
--- End diff --
Is it possible to throw UnsupportedOperationException instead?
> Data inconsistency issue due to the flaw in the session management
> ------------------------------------------------------------------
>
> Key: ZOOKEEPER-2926
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2926
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.5.3, 3.6.0
> Reporter: Fangmin Lv
> Assignee: Fangmin Lv
> Priority: Critical
>
> The local session upgrading feature will upgrade the session locally before
> receving a quorum commit of creating global session. It's possible that the
> server shutdown before the creating session request being sent to leader, if
> we retained the ZKDatabase or there is Snapshot happened just before
> shutdown, then only this server will have the global session.
> If that server didn't become leader, then it will have more global sessions
> than others, and those global sessions won't expire as the leader doesn't
> know it's existence. If the server became leader, it will accept the client
> renew session request and the client is allowed to create ephemeral nodes,
> which means other servers only have ephemeral nodes but not that global
> session. If there is follower going to have SNAP sync with it, then it will
> also have the global session. If the server without that global session
> becomes new leader, it will check and delete those dangling ephemeral node
> before serving traffic. These could introduce the issues that the ephemeral
> node being exist on some servers but not others.
> There is dangling global session issue even without local session feature,
> because on leader it will update the ZKDatabase when processing
> ConnectionRequest and in the PrepRequestProcessor before it's quorum
> committed, which also has this risk.
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