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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 Wed, 18 Feb 2009 06:53:01 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12674490#action_12674490
] 

dhruba borthakur commented on HADOOP-4663:
------------------------------------------

An offline discussion with Hairong, Sanjay, Rob Chansler, Raghu and Konstantin resulted in
these observations. 'bbw" refers to "blocksBeingWritten" directory.

1. leave blocks in bbw directory even when data restarts. only when the block is finalized
(when user closes the block or lease recovery occurs), does the block move to the real block
directory.
2. first block report (following a datanode registration) sends all blocks (including blocks
in bbw)
3. the block report processing on namenode  ignores blocks that are under construction
4. lease recovery should verify crc of block before they get promoted from bbw to real block
directory
5. When lease recovery ocurs, the datanode should terminate writer-threads before returning
length of block



> 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: 0.19.2
>
>         Attachments: appendQuestions.txt, 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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