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https://issues.apache.org/jira/browse/SSHD-646?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ke Xu updated SSHD-646:
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Comment: was deleted
(was: Would you please hint which version the "original code" is so we can use
that version? Thanks a lot.)
> ThreadGroup created in ThreadUtils is not destroyed and causes memory leak
> --------------------------------------------------------------------------
>
> Key: SSHD-646
> URL: https://issues.apache.org/jira/browse/SSHD-646
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 1.0.0
> Environment: linux
> Reporter: Ke Xu
> Assignee: Goldstein Lyor
> Fix For: 1.2.0
>
> Original Estimate: 8h
> Remaining Estimate: 8h
>
> ===============
> Problem description
> ===============
> In our application, we found that more than 250M memory were occupied by
> around 700,000 ThreadGroup objects (whose names are SshClient-nio2, timer,
> ClientInputStreamPump). The Threads contained in these ThreadGroups and their
> sub groups were all null.
> ===============
> Analysis
> ===============
> In ThreadUtils class there is an inner class named SshdThreadFactory. Inside
> this class, it will create a ThreadGroup and attach it to the parent
> Threadgroup:
> group = new ThreadGroup(parentGroup, "sshd-" + effectiveName + "-group");
> However, the destroy() method of the ThreadGroup object is never explicitely
> called when relevent resources are closed.
> According to ThreadGroup API, when a ThreadGroup is created with parent
> ThreadGroup specified, a reference to this child ThreadGroup is created in
> the parent. The destroy() method is the only way to make the parent to remove
> this reference.
> Thus in case the parent ThreadGroup is main, and there is a lot of
> ThreadGroup created, the ThreadGoup objects are not collected by the system
> until program exits. It will eventually occupy a lot of memory.
> ===============
> Suggested solution
> ===============
> A suggested solution is to mark the ThreadGroup object as daemon after it is
> created in SshdThreadFactory, e.g.:
> group = new ThreadGroup(parentGroup, "sshd-" + effectiveName +
> "-group");
> group.setDaemon(true);
> According to API, when a ThreadGroup is marked as daemon, it is automatically
> destroyed when its last thread is stopped or its last thread group is
> destroyed.
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