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https://issues.apache.org/jira/browse/HDFS-7225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14177307#comment-14177307
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Andrew Wang commented on HDFS-7225:
-----------------------------------
Nice examination here Zhe. One high-level question though, could we simplify
the above by cleaning InvalidateBlocks immediately upon seeing the new
datanodeUuid? If the old volume is brought back, the old blocks will be in the
block report and the NN will re-populate InvalidateBlocks as needed when it
processes the report.
> Failed DataNode lookup can crash NameNode with NullPointerException
> -------------------------------------------------------------------
>
> Key: HDFS-7225
> URL: https://issues.apache.org/jira/browse/HDFS-7225
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.6.0
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
> Attachments: HDFS-7225-v1.patch
>
>
> {{BlockManager#invalidateWorkForOneNode}} looks up a DataNode by the
> {{datanodeUuid}} and passes the resultant {{DatanodeDescriptor}} to
> {{InvalidateBlocks#invalidateWork}}. However, if a wrong or outdated
> {{datanodeUuid}} is used, a null pointer will be passed to {{invalidateWork}}
> which will use it to lookup in a {{TreeMap}}. Since the key type is
> {{DatanodeDescriptor}}, key comparison is based on the IP address. A null key
> will crash the NameNode with an NPE.
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