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From "Chen Liang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-11907) NameNodeResourceChecker should avoid calling df.getAvailable too frequently
Date Fri, 09 Jun 2017 21:59:18 GMT

     [ https://issues.apache.org/jira/browse/HDFS-11907?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chen Liang updated HDFS-11907:
------------------------------
    Attachment: HDFS-11907.006.patch

Thanks [~arpitagarwal] for pointing out offline that, {{checkAvailableResources}} has more
than one callers. Post v006 patch to move the measurement into this method to capture all
the callers.

> NameNodeResourceChecker should avoid calling df.getAvailable too frequently
> ---------------------------------------------------------------------------
>
>                 Key: HDFS-11907
>                 URL: https://issues.apache.org/jira/browse/HDFS-11907
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>         Attachments: HDFS-11907.001.patch, HDFS-11907.002.patch, HDFS-11907.003.patch,
HDFS-11907.004.patch, HDFS-11907.005.patch, HDFS-11907.006.patch
>
>
> Currently, {{HealthMonitor#doHealthChecks}} invokes {{NameNode#monitorHealth}} which
ends up invoking {{NameNodeResourceChecker#isResourceAvailable}}, at the frequency of once
per second by default. And NameNodeResourceChecker#isResourceAvailable invokes {{df.getAvailable();}}
every time it is called.
> Since available space information should rarely be changing dramatically at the pace
of per second. A cached value should be sufficient. i.e. only try to get the updated value
when the cached value is too old. otherwise simply return the cached value. This way df.getAvailable()
gets invoked less.
> Thanks [~arpitagarwal] for the offline discussion.



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