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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4663) Datanode should delete files under tmp when upgraded from 0.17
Date Wed, 07 Jan 2009 21:58:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12661732#action_12661732
] 

Konstantin Shvachko commented on HADOOP-4663:
---------------------------------------------

> In fact, the blocks here are not temporary any more.

This is the key. They are not temporary so why do we keep them in tmp directory? Why DNs cannot
report them to the name-node? It is just a matter of reporting the right length, right?

> disable "sync" on 0.18.3, will be an API incompatiblity from 0.18.2.

This is not incompatibility. The feature does not work correctly in 0.18.2 and it will still
not work correctly in 0.18.3 with the advantage of not causing all the problems.
I think removing everything under tmp as Raghu proposes is the right solution for 0.18.3.
We should talk about the "real" fix in terms of 0.19 and up. This seems to be a consensus
among colleagues around me.

> 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
>
>
> 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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