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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-988) saveNamespace can corrupt edits log
Date Fri, 06 May 2011 06:36:03 GMT

    [ https://issues.apache.org/jira/browse/HDFS-988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13029783#comment-13029783
] 

dhruba borthakur commented on HDFS-988:
---------------------------------------

1. we should not throw an exception is unable to update accesstime because NN is in safemode.
This will prevent a adminstrator from running read-only operations (dfs -cat) on a cluster
that is just starting up and is still in safemode. It shud just log a warning message and
continue

2. Unit test: Create a cluster, open a file for write and and put cluster in safemode. verify
that getAdditionalBlock, close, commitBlockSync etc fails when NN is in safemode 

> 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: 0.20-append, 0.21.0, 0.22.0
>            Reporter: dhruba borthakur
>            Assignee: Todd Lipcon
>            Priority: Blocker
>             Fix For: 0.20-append, 0.22.0
>
>         Attachments: hdfs-988-2.patch, 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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