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https://issues.apache.org/jira/browse/HADOOP-4663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12648264#action_12648264
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dhruba borthakur commented on HADOOP-4663:
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Actualy, on second thoughts, this does not seem to be a bug. For example, let's
say that we have a cluster that is running 0.20 release of hadoop. When you
restart a datanode, all files in the "tmp" directory need to be moved to the
real block directory. The reason being that a FileSystem.sync() call demands
that data once written to the datanode should persist. Thus, the problem you
are seeing is not related to cluster upgrade.
≥these files end up failing block verification and eventually get deleted. But
cause incorrect over-replication at the namenode before that.
Maybe we should try to improve the situation here. Is it possible to put the
blocks that got moved from "tmp" to the real block directory at the head of the
block-to-verify list so that their CRC validation occur first?
Another optimization (that i do not particularly like) is that the client can
tell the datanode if the client has invoked FileSystem.sync(). The Datanode can
persist this information. At datanode startup time, the Datanode moves only
those blocks that were marked as "synced" earlier.
> 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: 0.18.3
>
>
> 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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