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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-11817) A faulty node can cause a lease leak and NPE on accessing data
Date Fri, 12 May 2017 14:30:04 GMT
Kihwal Lee created HDFS-11817:

             Summary: A faulty node can cause a lease leak and NPE on accessing data
                 Key: HDFS-11817
                 URL: https://issues.apache.org/jira/browse/HDFS-11817
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 2.8.0
            Reporter: Kihwal Lee
            Priority: Critical

When the namenode performs a lease recovery for a failed write, the {{commitBlockSynchronization()}}
will fail, if none of the new target has sent a received-IBR.  At this point, the data is
inaccessible, as the namenode will throw a {{NullPointerException}} upon {{getBlockLocations()}}.

The lease recovery will be retried in about an hour by the namenode. If the nodes are faulty
(usually when there is only one new target), they may not block report until this point. If
this happens, lease recovery throws an {{AlreadyBeingCreatedException}}, which causes LeaseManager
to simply remove the lease without  finalizing the inode.  

This results in an inconsistent lease state. The inode stays under-construction, but no more
lease recovery is attempted. A manual lease recovery is also not allowed. 

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