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https://issues.apache.org/jira/browse/HDFS-11907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16044987#comment-16044987
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Chen Liang edited comment on HDFS-11907 at 6/9/17 8:37 PM:
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Thanks [~andrew.wang] for the comments. Based on Andrew's comments, instead of
making the change to cache the value, post v005 patch to add a metric to keep
track of available resource check time.
was (Author: vagarychen):
Thanks [~andrew.wang] for the comments. Based on Andrew's comments, instead of
making the cache the value, post v005 patch to add a metric to keep track of
available resource check time.
> 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
>
>
> 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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