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https://issues.apache.org/jira/browse/HDFS-8896?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14697316#comment-14697316
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Walter Su commented on HDFS-8896:
---------------------------------
The failed tests failed before the
patch([link|https://builds.apache.org/job/PreCommit-HDFS-Build/11989/testReport/]).
So it's not related.
> DataNode object isn't GCed when shutdown, because it has GC root in
> ShutdownHookManager
> ---------------------------------------------------------------------------------------
>
> Key: HDFS-8896
> URL: https://issues.apache.org/jira/browse/HDFS-8896
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: test
> Reporter: Walter Su
> Assignee: Walter Su
> Priority: Minor
> Attachments: HDFS-8896.01.patch, screenshot_1.PNG, screenshot_2.PNG
>
>
> The anonymous {{Thread}} object created in {{ShutdownHookManager}} is a GC
> root.
> screenshot_1 shows how DN object be traced to the GC root.
> It's not a problem in production.
> It's a problem in test, especially when MiniDFSCluster starts/shutdowns many
> DNs, which could cause {{OutOfMemoryError}}.
> screenshot_2 shows many DN objects are not GCed when run the test of
> HDFS-8838.
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