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https://issues.apache.org/jira/browse/HADOOP-4663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12668171#action_12668171
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Hairong Kuang commented on HADOOP-4663:
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I do believe that the generation-stamp-protocol should work. But I do not like
the idea of prompting blocks under the tmp directory. Blocks under tmp are
under-construction. Blindly finalizing them explicitly introduces polluted
blocks to the system and it completely depends on NN to clean them up. This
design seems to me not clean. Any minor error on the NN side might cost a lot.
Bugs like HADOOP-4810 caused Yahoo to lose quite amount of data and introduced
problems like HADOOP-4692 and other problems that we could not identify the
cause yet. I think it would be nice that DataNodes do not introduce pollution
in the first place.
> Datanode should delete files under tmp when upgraded from 0.17
> --------------------------------------------------------------
>
> Key: HADOOP-4663
> URL: https://issues.apache.org/jira/browse/HADOOP-4663
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.18.0
> Reporter: Raghu Angadi
> Assignee: dhruba borthakur
> Priority: Blocker
> Fix For: 0.19.1
>
> Attachments: deleteTmp.patch, deleteTmp2.patch, deleteTmp_0.18.patch,
> handleTmp1.patch
>
>
> Before 0.18, when Datanode restarts, it deletes files under data-dir/tmp
> directory since these files are not valid anymore. But in 0.18 it moves these
> files to normal directory incorrectly making them valid blocks. One of the
> following would work :
> - remove the tmp files during upgrade, or
> - if the files under /tmp are in pre-18 format (i.e. no generation), delete
> them.
> Currently effect of this bug is that, these files end up failing block
> verification and eventually get deleted. But cause incorrect over-replication
> at the namenode before that.
> Also it looks like our policy regd treating files under tmp needs to be
> defined better. Right now there are probably one or two more bugs with it.
> Dhruba, please file them if you rememeber.
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