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https://issues.apache.org/jira/browse/ZOOKEEPER-3131?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16597590#comment-16597590
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Fangmin Lv commented on ZOOKEEPER-3131:
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[~hw_wangchao] it was by design to leave it as is to improve the performance,
since the watcher number is usually related with the connections on that
server, and we can rely on the connection close to clean it up.
The problem here is that, NettyServerCnxn didn't remove itself from ZK server
as what we did in NIOServerCnxn, that's why it starts to leak slowly. I have a
patch to make the behavior consistent with NIOServerCnxn, I can send it out
today.
There are also other features missing comparing to NIO, for example, it's
missing the maximum cnxns per IP limit support, doesn't have cnxn expirer, the
NettyServerCnxnFactory.closeSession is not that efficient, etc. I'm recently
working on get netty prod ready, I'll send out other patches as well.
> org.apache.zookeeper.server.WatchManager resource leak
> ------------------------------------------------------
>
> Key: ZOOKEEPER-3131
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3131
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.5.3, 3.5.4
> Environment: -Xmx512m
> Reporter: ChaoWang
> Priority: Major
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> In some cases, the variable _watch2Paths_ in _Class WatchManager_ does not
> remove the entry, even if the associated value "HashSet" is empty already.
> The type of key in Map _watch2Paths_ is Watcher, instance of
> _NettyServerCnxn._ If it is not removed when the associated set of paths is
> empty, it will cause the memory increases little by little, and
> OutOfMemoryError triggered finally.
>
> {color:#FF0000}*Possible Solution:*{color}
> In the following function, the logic should be added to remove the entry.
> org.apache.zookeeper.server.WatchManager#removeWatcher(java.lang.String,
> org.apache.zookeeper.Watcher)
> if (paths.isEmpty())
> { watch2Paths.remove(watcher); }
> For the following function as well:
> org.apache.zookeeper.server.WatchManager#triggerWatch(java.lang.String,
> org.apache.zookeeper.Watcher.Event.EventType,
> java.util.Set<org.apache.zookeeper.Watcher>)
>
> Please confirm this issue?
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