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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15271863#comment-15271863
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Colin Patrick McCabe commented on HDFS-10301:
---------------------------------------------
Thanks for looking at this, [~daryn]. I'm not sure about the approach you
proposed, though. If interleaved full block reports really are very common for
[~shv], it seems like throwing an exception when these are received would be
problematic. It sounds like there might be some implementation concerns as
well, although I didn't look at the patch.
bq. [~shv] wrote: I don't think my approach requires RPC change, since the
block-report RPC message already has all required structures in place. It
should require only the processing logic change.
Just to be clear. If what is being sent over the wire is changing, I would
consider that an "RPC change." We can create an RPC change without modifying
the {{.proto}} file-- for example, by choosing not to fill in some optional
field, or filling in some other field.
bq. Colin, it would have been good to have an interim solution, but it does not
seem reasonable to commit a patch, which fixes one bug, while introducing
another.
The patch doesn't introduce any bugs. It does mean that we won't remove zombie
storages when interleaved block reports are received. But we are not handling
this correctly right now either, so that is not a regression.
Like I said earlier, I think your approach is a good one, but I think we should
get in the patch I posted here. It is a very small and non-disruptive change
which doesn't alter what is sent over the wire. It can easily be backported to
stable branches. Why don't we commit this patch, and then work on a follow-on
with the RPC change and simplification that you proposed?
> 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, 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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