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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15264772#comment-15264772
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Colin Patrick McCabe commented on HDFS-10301:
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bq. You can think of it as a new operation SyncStorages, which does just that -
updates NameNode's knowledge of DN's storages. I combined this operation with
the first br-RPC. One can combine it with any other call, same as you propose
to combine it with the heartbeat. Except it seems a poor idea, since we don't
want to wait for removal of thousands of replicas on a heartbeat.
Thanks for explaining your proposal a little bit more. I agree that
enumerating all the storages in the first block report RPC is a fairly simple
way to handle this, and shouldn't add too much size to the FBR. It seems like
a better idea than adding it to the heartbeat, like I proposed. In the short
term, however, I would prefer the current patch, since it involves no RPC
changes, and doesn't require all the DataNodes to be upgraded before it can
work.
> 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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