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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5889) When rolling upgrade is in progress, standby NN should create checkpoint for downgrade.
Date Tue, 11 Feb 2014 19:24:19 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13898184#comment-13898184
] 

Jing Zhao commented on HDFS-5889:
---------------------------------

The patch looks good to me. Besides image transferring, only one comment:
In the StandbyCheckpointer, if we are not in rolling upgrade, the nnf should still be NameNodeFile.IMAGE
instead of IMAGE_NEW?
{code}
-      img.saveNamespace(namesystem, canceler);
+      final NameNodeFile nnf = namesystem.isRollingUpgrade()?
+          NameNodeFile.IMAGE_UPGRADE: NameNodeFile.IMAGE_NEW;
+      img.saveNamespace(namesystem, nnf, canceler);
{code}

> When rolling upgrade is in progress, standby NN should create checkpoint for downgrade.
> ---------------------------------------------------------------------------------------
>
>                 Key: HDFS-5889
>                 URL: https://issues.apache.org/jira/browse/HDFS-5889
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: h5889_20140211.patch
>
>
> After rolling upgrade is started and checkpoint is disabled, the edit log may grow to
a huge size.  It is not a problem if rolling upgrade is finalized normally since NN keeps
the current state in memory and it writes a new checkpoint during finalize.  However, it is
a problem if admin decides to downgrade.  It could take a long time to apply edit log.  Rollback
does not have such problem.



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