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https://issues.apache.org/jira/browse/HDFS-11817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16016420#comment-16016420
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Kihwal Lee commented on HDFS-11817:
-----------------------------------

Hi, [~raviprak]. We've seen what you described above. It is not directly 
related to this jira, but I think we had an internal fix for this. Just a 
couple of days ago, we were talking about pushing the fix to Apache. Please do 
file a jira and let me know.

> 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
>            Assignee: Kihwal Lee
>            Priority: Critical
>         Attachments: hdfs-11817_supplement.txt
>
>
> 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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