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https://issues.apache.org/jira/browse/HDFS-12137?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kihwal Lee updated HDFS-12137:
------------------------------
       Resolution: Fixed
     Hadoop Flags: Reviewed
    Fix Version/s: 3.0.0-beta1
                   2.9.0
                   2.8.3
           Status: Resolved  (was: Patch Available)

Thanks for the review, [~xiaochen] and the patch, Daryn.

> DN dataset lock should be fair
> ------------------------------
>
>                 Key: HDFS-12137
>                 URL: https://issues.apache.org/jira/browse/HDFS-12137
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>    Affects Versions: 2.8.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>             Fix For: 2.8.3, 2.9.0, 3.0.0-beta1
>
>         Attachments: HDFS-12137.branch-2.patch, HDFS-12137.trunk.patch, 
> HDFS-12137.trunk.patch
>
>
> The dataset lock is very highly contended.  The unfair nature can be 
> especially harmful to the heartbeat handling.  Under high loads, partially 
> expose by HDFS-12136 introducing disk i/o within the lock, the heartbeat 
> handling thread may process commands so slowly due to the contention that the 
> node becomes stale or falsely declared dead.  The unfair lock is not helping 
> and appears to be causing frequent starvation under load.



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