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From "Xu Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-12332) Logging improvement suggestion for SampleStat function MinMax.add
Date Mon, 21 Aug 2017 15:37:00 GMT

     [ https://issues.apache.org/jira/browse/HDFS-12332?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Xu Zhao updated HDFS-12332:
    Attachment: hdfs-12332.patch

> Logging improvement suggestion for SampleStat function MinMax.add
> -----------------------------------------------------------------
>                 Key: HDFS-12332
>                 URL: https://issues.apache.org/jira/browse/HDFS-12332
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: metrics
>    Affects Versions: 3.0.0-alpha4
>            Reporter: Xu Zhao
>            Priority: Minor
>         Attachments: hdfs-12332.patch
> In order to debug performance anomlies, it is better to see when the max and min value
get updated in metrics.
> For example, in our workload we would like to see the longest latency of a write block
request on DataNode.
> The following metric updating code could possibly update the min/max value in SampleStat
> {code:java}
>     datanode.getMetrics().addWriteBlockOp(elapsed());
>     datanode.getMetrics().incrWritesFromClient(peer.isLocal(), size);
> {code}
> Here I am attaching an attempt to patch it.
> The patch just adds additional DEBUG level logging in the MinMax class and prints the
new value when it gets updated.
> Please let me know what you think. For example, if this patch would introduce too much
noises, what is the best way to trace the read/writeBlock that has the minimum/maximum latency?
> Any comments are appreciated!

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