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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-533) Region Historian
Date Thu, 29 May 2008 18:37:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12600872#action_12600872

stack commented on HBASE-533:

Should we just let this exception out rather than catch it:

+    } catch (IOException ioe) {
+      LOG.warn("Unable to create RegionHistorian", ioe);
+    }

Maybe these are not all needed -- +    getInstance(); -- especially when method calls cascade...
just call it in the method that terminates the cascade: i.e. the 'add' method (Minor issue).

Remove the commented out code in RegionHistorian

Perhaps make this class private and static (unless it has dependency on hosting class):

+  public class RegionHistoryInformation implements
+  Comparable<RegionHistoryInformation> {

Otherwise, patch looks good.

Lets get the migration added before we apply?  Unless you want to do that as separate task.
 If so, open new issue and I'll commit this.

Migrating, hopefully you can use MetaUtils.  If facility is missing, let me know and I'll
add it for you.

> 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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