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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3990) NN's health report has severe performance problems
Date Fri, 28 Sep 2012 13:43:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13465597#comment-13465597
] 

Daryn Sharp commented on HDFS-3990:
-----------------------------------

Enabling a nscd host cache helped mitigate the issue by reducing load times to a few seconds.
 However the namespace read lock is highly undesirable, and the repeated dns lookups are questionable.
                
> 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: name-node
>    Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>
> 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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