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https://issues.apache.org/jira/browse/HDFS-3990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13479207#comment-13479207
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Eli Collins commented on HDFS-3990:
-----------------------------------
A null peerHostname just means you don't match, since we also check "hostName"
which reported by the DataNode which the mini cluster explicitly sets we should
be good, that's the current behavior after all right? Ie the only thing we're
adding here is an additional hostname field to check, which is null and we
won't check in the tests. Related, would be good to make the minicluster match
real cluster behavior here.
> 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.branch-0.23.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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