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From "Jean-Daniel Cryans (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-533) Region Historian
Date Fri, 30 May 2008 14:26:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12601145#action_12601145
] 

Jean-Daniel Cryans commented on HBASE-533:
------------------------------------------

Regards RegionHistoryInformation, it is just a "nice" class carrying information that we get
out of .META. so has to be public or it would be useless. regionhistorian.jsp is currently
using it.

Regards region creations, it only happens when a table is created. Should it be removed?

Also I see that I forgot to process regions assignment, this will be included in the next
patch.

Regards the exception catch in RegionHistorian contructor, I think that if this fails, it
will fail elsewhere since the line throwing it is :

{quote}
      metaTable = new HTable(conf, META_TABLE_NAME);
{quote}

Regards merge, where is it thrown?

> Region Historian
> ----------------
>
>                 Key: HBASE-533
>                 URL: https://issues.apache.org/jira/browse/HBASE-533
>             Project: Hadoop HBase
>          Issue Type: Wish
>            Reporter: Bryan Duxbury
>            Assignee: Jean-Daniel Cryans
>            Priority: Minor
>         Attachments: hbase-533-v1-fix.patch, hbase-533-v1.patch, hbase-533-v2.patch
>
>
> Whenever we try to debug region splitting, assignment, compaction, etc. issues, we always
end up having to look in 1-20 different log files for cryptic names of regions and try to
piece together the chain of events ourselves. This is a challenging at best effort most of
the time.
> What would be very useful would be a new utility I've nicknamed the Region Historian.
You give it the text name of a region, and it will track down the log messages relevant to
it in the master and regionserver logs. Then, it will interleave the messages in such a way
that the timestamps correctly list the order of events. The result is a log summary that accurately
describes what happened to a region during it's lifetime, making it much easier to try and
figure out where something went wrong.
> Other things it could do would be replace cryptic log messages with simple events like
"the region was split into a and b", "the region was assigned to server x", and trace the
lineage of a region backwards to its parent before it came into existence.
> I'm sure there are other things we would think up that would be useful as well.

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