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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15308997#comment-15308997
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Colin Patrick McCabe commented on HDFS-10301:
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bq. Vinitha's patch adds one RPC only in the case when block reports are sent
in multiple RPCs.
The case where block reports are sent in multiple RPCs is exactly the case
where scalability is the most important, since it indicates that we have a
large number of blocks. My patch adds no new RPCs. If we are going to take an
alternate approach, it should not involve a performance regression.
bq. Could you please review the patch.
I did review the patch. I suggested adding an optional field in an existing
RPC rather than adding a new RPC, and stated that I was -1 on adding new RPC
load to the NN.
> 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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