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https://issues.apache.org/jira/browse/HDFS-3004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13231699#comment-13231699
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Eli Collins commented on HDFS-3004:
-----------------------------------
Feedback on the earlier version:
- Why is the following necessary (instead of mark(1))? Doesn't decode itself
still only read 1 byte?
{code}
in.mark(in.available());
{code}
- Why do we unconditionally skip/read/rewind now in getInputStream now? Isn't
this handled lazily?
- Per above now that we never throw EditLogInputException we can nuke the class
and its uses
- Can we avoid caching opcodes?
Nits:
- Better flag name than "-f" for always choose first? That sounds like
"-force", maybe "-chooseFirst"?
- Would "skipBrokenEdits" instead of "resync" be a better name for the new
param for readOp?
- Maybe call ELIS#rewind "putOp" instead since we're not necesarily rewinding
the stream?
- skipUntil javadoc should say "to a given transaction ID, or the end of stream
is reached"
> 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__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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