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From "Nicolas Spiegelberg (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-988) saveNamespace can corrupt edits log
Date Tue, 08 Jun 2010 18:31:16 GMT

     [ https://issues.apache.org/jira/browse/HDFS-988?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Nicolas Spiegelberg updated HDFS-988:
-------------------------------------

    Attachment: saveNamespace_20-append.patch

Version of saveNamespace for the 0.20-append branch.  This patch is needed for many of the
unit tests to pass.  Without, as DNs die via shutdown(), the remaining DNs get +1 seqnum.
So, only the last DN has the highest seqnum on restart, which messes up some tests. This actually
causes a real world problem then if the last DN has corrupt data. 

> saveNamespace can corrupt edits log
> -----------------------------------
>
>                 Key: HDFS-988
>                 URL: https://issues.apache.org/jira/browse/HDFS-988
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.21.0, 0.22.0, 0.20-append
>            Reporter: dhruba borthakur
>            Assignee: Todd Lipcon
>            Priority: Blocker
>         Attachments: hdfs-988.txt, saveNamespace.txt, saveNamespace_20-append.patch
>
>
> The adminstrator puts the namenode is safemode and then issues the savenamespace command.
This can corrupt the edits log. The problem is that  when the NN enters safemode, there could
still be pending logSycs occuring from other threads. Now, the saveNamespace command, when
executed, would save a edits log with partial writes. I have seen this happen on 0.20.
> https://issues.apache.org/jira/browse/HDFS-909?focusedCommentId=12828853&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12828853

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