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https://issues.apache.org/jira/browse/CURATOR-504?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16803430#comment-16803430
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Jordan Zimmerman commented on CURATOR-504:
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That gist has a few Curator lines and then a ton of ZooKeeper lines - is that
filtered? It would be nice to have more of the Curator log lines. Also, this
still may be the issue fixed in 4.2.0. Is this using 4.2.0 or an earlier
version?
> Race conditions in LeaderLatch after reconnecting to ensemble
> -------------------------------------------------------------
>
> Key: CURATOR-504
> URL: https://issues.apache.org/jira/browse/CURATOR-504
> Project: Apache Curator
> Issue Type: Bug
> Affects Versions: 4.1.0
> Reporter: Yuri Tceretian
> Assignee: Jordan Zimmerman
> Priority: Minor
> Attachments: 51868597-65791000-231c-11e9-9bfa-1def62bc3ea1.png,
> Screen Shot 2019-01-31 at 10.26.59 PM.png,
> XP91JuD048Nl_8h9NZpH01QZJMfCLewjfd2eQNfOsR6GuApPNV.png
>
>
> We use LeaderLatch in a lot of places in our system and when ZooKeeper
> ensemble is unstable and clients are reconnecting to logs are full of
> messages like the following:
> {{[2017-08-31
> 19:18:34,562][ERROR][org.apache.curator.framework.recipes.leader.LeaderLatch]
> Can't find our node. Resetting. Index: -1 {}}}
> According to the
> [implementation|https://github.com/apache/curator/blob/4251fe328908e5fca37af034fabc190aa452c73f/curator-recipes/src/main/java/org/apache/curator/framework/recipes/leader/LeaderLatch.java#L529-L536],
> this can happen in two cases:
> * When internal state `ourPath` is null
> * When the list of latches does not have the expected one.
> I believe we hit the first condition because of races that occur after client
> reconnects to ZooKeeper.
> * Client reconnects to ZooKeeper and LeaderLatch gets the event and calls
> reset method which set the internal state (`ourPath`) to null, removes old
> latch and creates a new one. This happens in thread
> "Curator-ConnectionStateManager-0".
> * Almost simultaneously, LeaderLatch gets another even NodeDeleted
> ([here|https://github.com/apache/curator/blob/4251fe328908e5fca37af034fabc190aa452c73f/curator-recipes/src/main/java/org/apache/curator/framework/recipes/leader/LeaderLatch.java#L543-L554])
> and tries to re-read the list of latches and check leadership. This happens
> in the thread "main-EventThread".
> Therefore, sometimes there is a situation when method `checkLeadership` is
> called when `ourPath` is null.
> Below is an approximate diagram of what happens:
> !51868597-65791000-231c-11e9-9bfa-1def62bc3ea1.png|width=1261,height=150!
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