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https://issues.apache.org/jira/browse/HDFS-12332?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Brahma Reddy Battula updated HDFS-12332:
----------------------------------------
    Target Version/s: 3.4.0  (was: 3.3.0)

Bulk update: moved all 3.3.0 non-blocker issues, please move back if it is a 
blocker.



> 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 class:
> {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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