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From "Jonathan Hsieh (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5360) [uberhbck] Add options for how to handle offline split parents.
Date Fri, 13 Apr 2012 07:02:32 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5360?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13253187#comment-13253187
] 

Jonathan Hsieh commented on HBASE-5360:
---------------------------------------

@Anoop.  Partially.  HBASE-5719 sidelines potential overlapping regions but doesn't take .META.'s
info about if the region is offline into account.  It could sideline a live region while it
could have been more efficient to sideline an offline region.  However, HBASE-5719 was sufficient
for the case we were dealing with.  

Let's make this a placeholder for ways to improve it.  Some ideas include:
* Taking a region's offline/splitparent state into account if .META. entry is present
* Making decisions about sidelining vs merging based on region size and max region size (instead
of range) xml properties.
* Improving the heuristic used to decide which region are sidelined.


                
> [uberhbck] Add options for how to handle offline split parents. 
> ----------------------------------------------------------------
>
>                 Key: HBASE-5360
>                 URL: https://issues.apache.org/jira/browse/HBASE-5360
>             Project: HBase
>          Issue Type: Improvement
>          Components: hbck
>    Affects Versions: 0.90.7, 0.92.1, 0.94.0
>            Reporter: Jonathan Hsieh
>
> In a recent case, we attempted to repair a cluster that suffered from HBASE-4238 that
had about 6-7 generations of "leftover" split data.  The hbck repair options in an development
version of HBASE-5128 treat HDFS as ground truth but didn't check SPLIT and OFFLINE flags
only found in meta.  The net effect was that it essentially attempted to merge many regions
back into its eldest geneneration's parent's range.  
> More safe guards to prevent "mega-merges" are being added on HBASE-5128.
> This issue would automate the handling of the "mega-merge" avoiding cases such as "lingering
grandparents".  The strategy here would be to add more checks against .META., and perform
part of the catalog janitor's responsibilities for lingering grandparents.  This would potentially
include options to sideline regions, deleting grandparent regions, min size for sidelining,
and mechanisms for cleaning .META..  
> Note: There already exists an mechanism to reload these regions -- the bulk loaded mechanisms
in LoadIncrementalHFiles can be used to re-add grandparents (automatically splitting them
if necessary) to HBase.

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