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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15317644#comment-15317644
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Colin Patrick McCabe commented on HDFS-10301:
---------------------------------------------
Sorry for the slow reply. I was on vacation.
Like I said earlier, I am -1 on patch v4 because adding new RPCs is bad for NN
scalability. I also think it's a much larger patch than needed. It doesn't
make sense as an interim solution.
Why don't we commit v5 and discuss improvements in a follow-on JIRA? So far
there is no concrete argument against it other than the fact that it doesn't
remove zombie storages in the case where BRs are interleaved. But we already
know that BR interleaving is an extremely rare corner case-- otherwise you can
bet that this JIRA would have attracted a lot more attention.
> 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-10301.004.patch, HDFS-10301.005.patch, HDFS-10301.01.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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