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From "Erik Krogen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-11615) FSNamesystemLock metrics can be inaccurate due to millisecond precision
Date Thu, 13 Apr 2017 00:15:42 GMT

     [ https://issues.apache.org/jira/browse/HDFS-11615?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Erik Krogen updated HDFS-11615:
-------------------------------
    Attachment: HDFS-11615.001.patch

Ah, thanks [~zhz], didn't realize there was precedent for this already. Sounds good then!
Uploading v001 patch which adds Nanos to the name and marks all of the variables in the class
with their unit.

> 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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