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https://issues.apache.org/jira/browse/HADOOP-3776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12624676#action_12624676
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Hudson commented on HADOOP-3776:
--------------------------------
Integrated in Hadoop-trunk #581 (See
[http://hudson.zones.apache.org/hudson/job/Hadoop-trunk/581/])
> NPE in NameNode with unknown blocks
> -----------------------------------
>
> Key: HADOOP-3776
> URL: https://issues.apache.org/jira/browse/HADOOP-3776
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.18.0
> Reporter: Raghu Angadi
> Assignee: Raghu Angadi
> Priority: Blocker
> Fix For: 0.18.0, 0.19.0
>
> Attachments: HADOOP-3776-branch-018.patch, HADOOP-3776.patch,
> HADOOP-3776.patch, HADOOP-3776.patch
>
>
> When a datanode has a block that NameNode does not have, it results in an NPE
> at the NameNode. And one of these cases results in an infinite loop of these
> errors because DataNode keeps invoking the same RPC that resulted in this NPE.
> One way to reproduce :
> * On a single DN cluster, start writing a large file (something like
> {{'bin/hadoop fs -put 5Gb 5Gb'}})
> * Now, from a different shell, delete this file ({{bin/hadoop fs -rm 5Gb}})
> * Most likely you will hit this.
> * The cause is that when DataNode invokes {{blockReceived()}} to inform
> about the last block it received, the file is already deleted and results in
> an NPE at the namenode. The way DataNode works, it basically keep invoking
> the same RPC with same block and results in the same error.
> When block does not exist in NameNode's blocksMap, it basically does not
> belong to the cluster. Let me know if you need the trace. Basically the NPE
> is at FSNamesystem.java:2800 (on trunk).
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