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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15259278#comment-15259278
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Konstantin Shvachko commented on HDFS-10301:
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Hey Colin, I reviewed your patch more thoroughly. There is still a problem with
interleaving reports. See {{updateBlockReportContext()}}. Suppose that block
reports interleave like this: <br1-s1, br2-s1, br1-s2, br2-s2>. Then br1-s2
will reset {{curBlockReportRpcsSeen}} since {{curBlockReportId}} is not the
same as in the report, which will discard the bit set for s1 in br2-s1, and the
count of {{rpcsSeen = 0}} will be wrong for br2-s2. So possibly unreported
(zombie) storages will not be removed. LMK if you see what I see.
> 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: Colin Patrick McCabe
> Priority: Critical
> Attachments: HDFS-10301.002.patch, HDFS-10301.003.patch,
> HDFS-10301.01.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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