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https://issues.apache.org/jira/browse/HDFS-5693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13977628#comment-13977628
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Jing Zhao commented on HDFS-5693:
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The new patch actually still includes the quick check in listCorruptFileBlocks
:) But we can make further changes in HDFS-6272. +1 pending Jenkins.
> Few NN metrics data points were collected via JMX when NN is under heavy load
> -----------------------------------------------------------------------------
>
> Key: HDFS-5693
> URL: https://issues.apache.org/jira/browse/HDFS-5693
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: Ming Ma
> Assignee: Ming Ma
> Attachments: HADOOP-5693.patch, HDFS-5693-2.patch, HDFS-5693.patch
>
>
> JMX sometimes doesn’t return any value when NN is under heavy load. However,
> that is when we would like to get metrics to help to diagnosis the issue.
> When NN is under heavy load due to bad application or other reasons, it holds
> FSNamesystem's writer lock for a long period of time. Many of the
> FSNamesystem metrics require FSNamesystem's reader lock and thus can't be
> processed.
> This is a special case to improve the overall NN concurrency.
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