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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15386702#comment-15386702
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Konstantin Shvachko commented on HDFS-10301:
--------------------------------------------

My general approach to protobuf structures is to minimize changes, especially 
with redundant fields.
It is very easy to add fields, as you demonstrated, but you can never remove 
them.
So add them only if you absolutely must.
But different people can of course have different approaches.

> BlockReport retransmissions may lead to storages falsely being declared 
> zombie if storage report processing happens out of order
> --------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-10301
>                 URL: https://issues.apache.org/jira/browse/HDFS-10301
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.6.1
>            Reporter: Konstantin Shvachko
>            Assignee: Vinitha Reddy Gankidi
>            Priority: Critical
>         Attachments: HDFS-10301.002.patch, HDFS-10301.003.patch, 
> HDFS-10301.004.patch, HDFS-10301.005.patch, HDFS-10301.006.patch, 
> HDFS-10301.007.patch, HDFS-10301.008.patch, HDFS-10301.009.patch, 
> HDFS-10301.01.patch, HDFS-10301.010.patch, HDFS-10301.011.patch, 
> HDFS-10301.sample.patch, zombieStorageLogs.rtf
>
>
> When NameNode is busy a DataNode can timeout sending a block report. Then it 
> sends the block report again. Then NameNode while process these two reports 
> at the same time can interleave processing storages from different reports. 
> This screws up the blockReportId field, which makes NameNode think that some 
> storages are zombie. Replicas from zombie storages are immediately removed, 
> causing missing blocks.



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