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https://issues.apache.org/jira/browse/HDFS-3004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13247953#comment-13247953
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Colin Patrick McCabe commented on HDFS-3004:
--------------------------------------------
Hmm. I always run -format from within a script, and it never prompts. Looking
at the script, it seems that the reason is because the script deletes the
metadata directories beforehand, and -format is smart enough to recognize this
and skip the prompt in the case where there are no existing metadata
directories.
Anyway, I stand corrected. If -format by default requires a prompt, then
recovery mode can as well.
I suppose we can display this prompt even when -force is specified, too. Just
one prompt at the beginning. I don't think recovery mode is the sort of thing
that we'll be putting into scripts any time soon.
Anyway, if anyone else has any input on this, please post. Otherwise I'll make
the changes mentioned above in the next patch.
> 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__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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