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From hanm <...@git.apache.org>
Subject [GitHub] zookeeper pull request #211: ZOOKEEPER-2743: Netty connection leaks JMX conn...
Date Sat, 01 Apr 2017 20:59:31 GMT
GitHub user hanm opened a pull request:


    ZOOKEEPER-2743: Netty connection leaks JMX connection bean.

    See https://issues.apache.org/jira/browse/ZOOKEEPER-2743 for details on the symptom and
    There are many ways of fixing this. For example we can enforce certain ordering of the
close operations to eliminate the race condition however that would incur non trivial performance
penalty as a result of synchronization. I think the solution in this patch is simple and effective
as it observes that the bean unregister call is idempotent and the call itself is trivial
so we just always unregister connection upon close the connection, to ensure the bean is unregistered
regardless of the races.
    I've also stress tested this solution on internal Jenkins which indicates no failures
of https://issues.apache.org/jira/browse/ZOOKEEPER-2707 for the past two days.
    A side note is NIO connection in theory would suffer the same problem however I am unable
to reproduce the same racing with existing unit test. So I just leave NIO as it is, for now.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/hanm/zookeeper ZOOKEEPER-2743

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #211
commit 7dd916c4c7c8d4e0e83cb5780175058a5626de19
Author: Michael Han <hanm@apache.org>
Date:   2017-04-01T20:37:48Z

    ZOOKEEPER-2743: Netty connection leaks JMX connection bean upon connection close in certain
race conditions.
    Always unregister connection upon close to prevent connection bean leak under certain
race conditions.


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