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https://issues.apache.org/jira/browse/ZOOKEEPER-2926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16324395#comment-16324395
]
ASF GitHub Bot commented on ZOOKEEPER-2926:
-------------------------------------------
Github user lvfangmin commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/447#discussion_r161296493
--- Diff:
src/java/main/org/apache/zookeeper/server/PrepRequestProcessor.java ---
@@ -579,13 +579,8 @@ protected void pRequest2Txn(int type, long zxid,
Request request,
int to = request.request.getInt();
request.setTxn(new CreateSessionTxn(to));
request.request.rewind();
- if (request.isLocalSession()) {
- // This will add to local session tracker if it is
enabled
- zks.sessionTracker.addSession(request.sessionId, to);
- } else {
- // Explicitly add to global session if the flag is not
set
- zks.sessionTracker.addGlobalSession(request.sessionId,
to);
- }
+ // only add the global session tracker but not to ZKDb
+ zks.sessionTracker.addGlobalSession(request.sessionId, to);
--- End diff --
On LeaderSessionTracker, we need to differentiate add local session or
global session, but since we only call createSession when add local session, I
think I can simplify the interface more by removing addGlobalSession and rename
addSession to trackSession.
> 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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