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Date: Thu, 29 May 2008 12:03:45 -0700 (PDT)
From: "Jean-Daniel Cryans (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Commented: (HBASE-533) Region Historian
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    [ https://issues.apache.org/jira/browse/HBASE-533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12600883#action_12600883 ] 

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

bq. 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.

Yes, before.

bq. Does the region run merges? You should add flush. Do you mean RegionServer in the above rather than Regions?

package region

bq. There are no creations any more. Is that because happens elsewhere - in parent? - so doesn't show in a particular region.

There is, look at a region that was created with a table. Regions that are created from a split don't pass by HRegion.createHRegion. Rebooting your cluster will also put creations in all regions.


I'm OK with the rest.


> 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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