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https://issues.apache.org/jira/browse/HDFS-7225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14179124#comment-14179124
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Zhe Zhang commented on HDFS-7225:
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Sure we should cleanup when a DN is removed. {{wipeDatanode}} looks right place
to me, being the only method calling {{datanodeMap.remove()}}. I think we
should also keep the cleanup at lookup time in case elements are removed from
{{datanodeMap}} unexpectedly.
Thinking a little more about our previous assumption below:
bq. 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.
How about file deletions? With our current approach would there be orphan
blocks when the volume comes back?
> 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, HDFS-7225-v2.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 However, if a wrong or outdated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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