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https://issues.apache.org/jira/browse/HDFS-13775?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18047837#comment-18047837
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ASF GitHub Bot commented on HDFS-13775:
---------------------------------------

github-actions[bot] closed pull request #406: HDFS-13775. Add a conf property 
to retry dns reverse lookups during datanode registration.
URL: https://github.com/apache/hadoop/pull/406




> Add a conf property to retry dns reverse lookups during datanode registration
> -----------------------------------------------------------------------------
>
>                 Key: HDFS-13775
>                 URL: https://issues.apache.org/jira/browse/HDFS-13775
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>            Reporter: Aniket Namadeo Mokashi
>            Priority: Major
>              Labels: pull-request-available
>
> During DN registration, if the ip and the hostname in the DN InetAddress are 
> the same (i.e. reverse name lookup falied; see [the 
> javadoc|http://docs.oracle.com/javase/6/docs/api/java/net/InetAddress.html#getHostName%28%29]),
>  the DN will be disallowed to register, where the DN InetAddress was obtained 
> from the socket. It is a performance improvement added by HDFS-3990 to avoid 
> unnecessary DNS resolutions. However, in an environment where DNS lookups can 
> be flaky this can cause datanode registration to fail permanently.
> We propose to add a conf property to retry DNS reverse lookup during DN 
> registration. Otherwise, clusters with flaky reverse DNS lookup will fail 
> permanently.



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