[jira] [Commented] (HDFS-3990) NN's health report has severe performance problems

["Tsz Wo (Nicholas), SZE (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-3990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13791096#comment-13791096 ] 

Tsz Wo (Nicholas), SZE commented on HDFS-3990:
----------------------------------------------

The hostname.equals(ip) check added to DatanodeManager.registerDatanode(..) may not work for existing clusters which do not have reverse DNS lookup support; filed HDFS-5338.

> NN's health report has severe performance problems
> --------------------------------------------------
>
>                 Key: HDFS-3990
>                 URL: https://issues.apache.org/jira/browse/HDFS-3990
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>             Fix For: 3.0.0, 2.0.3-alpha, 0.23.5
>
>         Attachments: HDFS-3990.branch-0.23.patch, HDFS-3990.branch-0.23.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, HDFS-3990.patch, hdfs-3990.txt, hdfs-3990.txt
>
>
> The dfshealth page will place a read lock on the namespace while it does a dns lookup for every DN.  On a multi-thousand node cluster, this often results in 10s+ load time for the health page.  10 concurrent requests were found to cause 7m+ load times during which time write operations blocked.



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