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From "Jordan Zimmerman (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CURATOR-62) Leader Election Deadlock
Date Mon, 07 Oct 2013 16:02:44 GMT

     [ https://issues.apache.org/jira/browse/CURATOR-62?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jordan Zimmerman updated CURATOR-62:
------------------------------------

    Affects Version/s: 2.2.0-incubating

> Leader Election Deadlock
> ------------------------
>
>                 Key: CURATOR-62
>                 URL: https://issues.apache.org/jira/browse/CURATOR-62
>             Project: Apache Curator
>          Issue Type: Bug
>          Components: Recipes
>    Affects Versions: 2.2.0-incubating
>            Reporter: Doug Jones
>            Assignee: Jordan Zimmerman
>
> I've noticed that it is possible for a leader election to deadlock if a thread is interrupted
while it is trying to acquire the mutex for the election.
> I've created a forced example of this here: https://github.com/dfjones/curator/commit/544220b1e6b51c2718a7d3511a74962ff1c5ff48
> You can see deadlock by using my modified code and running the LeaderSelectorExample.
Some leaders may execute, but on my system I eventually see deadlock. Note that I only see
deadlock when running against a remote zk server rather than the embedded test server. I'm
using Zookeeper 3.4.5 on Mac OS X 10.8.4.
> From what I can tell by inspecting the ZK state/watching in the debugger, the thread
that is interrupted is able to successfully create the lock object in ZK. However, due to
the interrupt an exception is generated and LockInternals#internalLockLoop never runs. Later,
in LeaderSelector#doWork when mutex.release() is called this fails at the for lockData.
> Once this occurs, the lock object in ZK is the oldest and will cause deadlock.



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