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https://issues.apache.org/jira/browse/HDFS-988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13042351#comment-13042351
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Eli Collins commented on HDFS-988:
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It looks like most of the unprotected* methods take the rwlock, but don't need
to because either because their caller takes the lock or they are called from
loading the edit log (which is why we originally had unprotected versions). Do
people mind if I fix that up (remove the locking from these methods, make sure
the unprotected versions are only called when loading the log) in this change
or do people want that done in a separate change?
> saveNamespace can corrupt edits log, apparently due to race conditions
> ----------------------------------------------------------------------
>
> 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: Eli Collins
> Priority: Blocker
> Fix For: 0.20-append, 0.22.0
>
> Attachments: HDFS-988_fix_synchs.patch, hdfs-988-2.patch,
> hdfs-988-3.patch, hdfs-988-4.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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