Kihwal Lee created HDFS-5850:
--------------------------------

             Summary: DNS Issues during TrashEmptier initialization can 
silently leave it non-functional
                 Key: HDFS-5850
                 URL: https://issues.apache.org/jira/browse/HDFS-5850
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 2.4.0
            Reporter: Kihwal Lee
            Priority: Critical


[~knoguchi] once noticed that the trash directories of a restarted cluster are 
not cleaned up. It turned out that it was caused by a transient DNS problem 
during initialization.

TrashEmptier thread in namenode is actually a FileSystem client running in a 
loop, which makes RPC calls to itself in order  to list, rename and delete 
trash files.  In a secure setup, the client needs to create the right service 
principal name for the namenode for making a RPC connection. If there is a DNS 
issue at that moment, the SPN ends up with the IP address, not the fqdn.

Since KDC does not recognize this SPN, TrashEmptier does not work from that 
point on. I verified that the SPN with the IP address was what the TrashEmptier 
thread asked KDC for a service ticket for.



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