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Date: Sat, 13 Apr 2013 00:36:16 +0000 (UTC)
From: "Shevek (JIRA)" <jira@apache.org>
To: dev@curator.incubator.apache.org
Message-ID: <JIRA.12642354.1365813345571.161150.1365813376684@arcas>
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Subject: [jira] [Created] (CURATOR-15) LeaderSelector may (undetectably)
 fail to elect
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Shevek created CURATOR-15:
-----------------------------

             Summary: LeaderSelector may (undetectably) fail to elect
                 Key: CURATOR-15
                 URL: https://issues.apache.org/jira/browse/CURATOR-15
             Project: Apache Curator
          Issue Type: Bug
            Reporter: Shevek
            Assignee: Jordan Zimmerman


In LeaderSelector, if mutex.acquire() throws an Exception, for example because CuratorFramework.getZooKeeper() threw a previously-enqueued background exception, then that failure will propagate out of doWork and doWorkLoop, and kill the background submission onto the executor service.

This means that a leaderselector which was start()ed will NEVER elect, and this situation is NOT DETECTABLE externally, since that exception happens on a private executorservice thread and is not client visible. It's impossible to look at a LeaderSelector and decide whether it is still "viable".

This can leave a machine/process "hung" and not automatically recoverable within curator.

Either isQueued() needs to be exposed, which means that a leader is either elected or queued; or the finally{} block which calls clearIsQueued() needs also to set state to CLOSED or FAILED, so that we can query this failure externally.

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