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https://issues.apache.org/jira/browse/HDFS-11817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16025471#comment-16025471
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Daryn Sharp commented on HDFS-11817:
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+1 I would be nice if this recovery code was cleaned up someday, but this
definitely fixes the perma-UC files and NPEs.
> 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.branch-2.patch, hdfs-11817_supplement.txt,
> HDFS-11817.v2.branch-2.patch, HDFS-11817.v2.trunk.patch
>
>
> 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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