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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11615) FSNamesystemLock metrics can be inaccurate due to millisecond precision
Date Mon, 17 Apr 2017 23:46:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15971828#comment-15971828
] 

Hudson commented on HDFS-11615:
-------------------------------

SUCCESS: Integrated in Jenkins build Hadoop-trunk-Commit #11595 (See [https://builds.apache.org/job/Hadoop-trunk-Commit/11595/])
HDFS-11615. FSNamesystemLock metrics can be inaccurate due to (zhz: rev ad49098eb324e238d97db68d7239ed2c4d84afa0)
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSNamesystemLock.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystemLock.java


> 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
>         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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