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From "Tsz Wo (Nicholas), SZE (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3004) Implement Recovery Mode
Date Sat, 07 Apr 2012 01:39:17 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13249118#comment-13249118
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Tsz Wo (Nicholas), SZE commented on HDFS-3004:
----------------------------------------------

{quote}
- Please remove createRecoveryContext() from HdfsServerConstants. It does not sound like a
constant.
{quote}
Hi Colin, you have not responded the above comment.

{quote}
There are no other options for recovery mode except autoChooseDefault. Check the usage or
run -h for more information.
{quote}
Then would it show an error message for the invalid options, say "hadoop namenode -format
-force" or "hadoop namenode -force"?

{quote}
> Why askOperator(..) belongs to FSEditLogLoader but not RecoveryContext?

Because it relates to FSEditLogLoader, not to RecoveryContext.
{quote}
It seems related to MetaRecoveryContext more: 
- it is a static method and have MetaRecoveryContext as a parameter
- it throws MetaRecoveryContext.RequestStopException
- it uses MetaRecoveryContext.LOG
                
> Implement Recovery Mode
> -----------------------
>
>                 Key: HDFS-3004
>                 URL: https://issues.apache.org/jira/browse/HDFS-3004
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: tools
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>         Attachments: HDFS-3004.010.patch, HDFS-3004.011.patch, HDFS-3004.012.patch, HDFS-3004.013.patch,
HDFS-3004.015.patch, HDFS-3004.016.patch, HDFS-3004.017.patch, HDFS-3004.018.patch, HDFS-3004.019.patch,
HDFS-3004.020.patch, HDFS-3004.022.patch, HDFS-3004.023.patch, HDFS-3004.024.patch, HDFS-3004.026.patch,
HDFS-3004.027.patch, HDFS-3004.029.patch, HDFS-3004.030.patch, HDFS-3004.031.patch, HDFS-3004.032.patch,
HDFS-3004.033.patch, HDFS-3004.034.patch, HDFS-3004.035.patch, HDFS-3004.036.patch, HDFS-3004.037.patch,
HDFS-3004.038.patch, HDFS-3004.039.patch, HDFS-3004.040.patch, HDFS-3004.041.patch, HDFS-3004.042.patch,
HDFS-3004.042.patch, HDFS-3004.042.patch, HDFS-3004__namenode_recovery_tool.txt
>
>
> When the NameNode metadata is corrupt for some reason, we want to be able to fix it.
 Obviously, we would prefer never to get in this case.  In a perfect world, we never would.
 However, bad data on disk can happen from time to time, because of hardware errors or misconfigurations.
 In the past we have had to correct it manually, which is time-consuming and which can result
in downtime.
> Recovery mode is initialized by the system administrator.  When the NameNode starts up
in Recovery Mode, it will try to load the FSImage file, apply all the edits from the edits
log, and then write out a new image.  Then it will shut down.
> Unlike in the normal startup process, the recovery mode startup process will be interactive.
 When the NameNode finds something that is inconsistent, it will prompt the operator as to
what it should do.   The operator can also choose to take the first option for all prompts
by starting up with the '-f' flag, or typing 'a' at one of the prompts.
> I have reused as much code as possible from the NameNode in this tool.  Hopefully, the
effort that was spent developing this will also make the NameNode editLog and image processing
even more robust than it already is.

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