Aniket Mokashi created HDFS-13775:
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             Summary: 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 Mokashi


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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