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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4663) Datanode should delete files under tmp when upgraded from 0.17
Date Thu, 15 Jan 2009 01:03:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12663958#action_12663958
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dhruba borthakur commented on HADOOP-4663:
------------------------------------------

I think the issue that Konstantin is raising is based on the assumption that data that is
not "synced" by a client *should not* appear in a file. This assumption is not true as specified
in the design document for Appends. The guarantee is that data that is written prior to a
"sync" call will be seen by all new readers of the file.

Just like in any UNIX-y systems, data that is not "sync" can still be seen by other concurrent
readers. 

> 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
>
>         Attachments: deleteTmp.patch, deleteTmp2.patch, deleteTmp_0.18.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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