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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5999) Do not create rollback fsimage when it already exists
Date Sun, 23 Feb 2014 06:22:19 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13909686#comment-13909686
] 

Tsz Wo (Nicholas), SZE commented on HDFS-5999:
----------------------------------------------

Patch looks good.  A minor suggestion: Let's call hasRollbackFSImage in FSEditLogLoader. 
Then, we could keep the saveNamespace parameter in startRollingUpgradeInternal.  Passing txid
is harder to understand.

> Do not create rollback fsimage when it already exists
> -----------------------------------------------------
>
>                 Key: HDFS-5999
>                 URL: https://issues.apache.org/jira/browse/HDFS-5999
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, ha, hdfs-client, namenode
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-5999.000.patch
>
>
> Currently in FSEditLogLoader#applyEditLogOp, if the op is OP_START_LOG_SEGMENT, we do
an extra rollback fsimage with condition "totalEdits > 1".
> This may cause some issue when we restart a NN with new software. If there is no extra
checkpoint after the rollback image, the NN may generate a new rollback image using the new
software, and replace the old rollback image. Then later if we want to do rollback the NN,
which uses the old software, may not be able to load the rollback image.



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