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From "Eli Collins (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3990) NN's health report has severe performance problems
Date Mon, 15 Oct 2012 20:47:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13476429#comment-13476429

Eli Collins commented on HDFS-3990:

Why not use the DatanodeID hostName field instead of calling and caching InetAddress#getByName
in the NN? The DN has already done the lookup (modulo the tests which use dfs.datanode.hostname)
and this way we don't have to worry about inconsistency between the nodeAddr and the ipAddr/hostName
fields. For sanity the NN could do a lookup when the DN registers and compare it's value to
the DN reported one.

Comments on this patch:
- In registerDatanode why is OK to no longer update the registration info with the reported
- The comments in DatanodeManager ("Mostly called inside an RPC.".. and "Update the IP to
the address of the RPC request"..) are no longer accurate after your change.
> 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
>         Attachments: HDFS-3990.patch, HDFS-3990.patch
> 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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