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https://issues.apache.org/jira/browse/HDFS-11615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17281562#comment-17281562
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tomscut commented on HDFS-11615:
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To monitor how often read/write locks exceed thresholds, we can add two
metrics(ReadLockWarning/WriteLockWarning), which are exposed in JMX.
Hi [~xkrogen], could you please review the code? Thanks a lot!
[https://github.com/apache/hadoop/pull/2668]
> FSNamesystemLock metrics can be inaccurate due to millisecond precision
> -----------------------------------------------------------------------
>
> Key: HDFS-11615
> URL: https://issues.apache.org/jira/browse/HDFS-11615
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs
> Affects Versions: 2.7.4
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Major
> Fix For: 2.9.0, 2.7.4, 3.0.0-alpha4, 2.8.2
>
> Attachments: HDFS-11615.000.patch, HDFS-11615.001.patch
>
>
> Currently the {{FSNamesystemLock}} metrics created in HDFS-10872 track the
> lock hold time using {{Timer.monotonicNow()}}, which has millisecond-level
> precision. However, many of these operations hold the lock for less than a
> millisecond, making these metrics inaccurate. We should instead use
> {{System.nanoTime()}} for higher accuracy.
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