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https://issues.apache.org/jira/browse/HADOOP-4663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12665542#action_12665542
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Konstantin Shvachko commented on HADOOP-4663:
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Append or not if we want files be visible by other clients there should be a
logic which reads files in the tmp directory. And this is not related to
promoting incomplete files. We do not have guarantees for the data to survive
crashes if it has not been sync-ed even if another client has seen it.
> the "append" protocol uses the generation stamp to accurately determine stale
> blocks
> it is safe to promote blocks from the "blocksBeingWritten" directory
If the protocol worked correctly it would be safe to promote any incomplete
blocks including those in blocksBeingReplicated but it wasn't.
I would rather not promote unsynced files because
# it turned to be error-prone
# it adds performance overhead, when sync or append is not used.
> 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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