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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 Wed, 31 May 2017 19:28:05 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-11907.002.patch

Post v002 patch to merge the change from HDFS-11906, which adds a log warning if {{NameNode#monitorHealth}}
is taking too long.

> 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
>
>
> 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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