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From "ramkrishna.s.vasudevan (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5737) Minor Improvements related to balancer.
Date Tue, 10 Apr 2012 18:07:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250890#comment-13250890
] 

ramkrishna.s.vasudevan commented on HBASE-5737:
-----------------------------------------------

@Zhihong
Thanks for your review.  
If you see the code base where we deal with the regions assignment like the 
{code}
  private final NavigableMap<ServerName, Set<HRegionInfo>> servers =
    new TreeMap<ServerName, Set<HRegionInfo>>();
{code}
{code}
  private final SortedMap<HRegionInfo, ServerName> regions =
    new TreeMap<HRegionInfo, ServerName>();
{code}
We use treemap.  Here in getAssignmentsByTable we try to give the table to region, server
mapping.
The places where we do rebuildUserRegions also we try to maintain the order as retrieved from
the meta.
Here also we try to iterate the 'servers' tree map and form the result.  Hence i felt using
a tree map will maintain some consistency.
And for some real world scenario, if i have a pair of tables may be named TableA and TableA_xxxx
then when i want to do a balancing for these two tables thro an extended balancer there is
a chance that TableA_xxxx comes first and then TableA.  But this use case is very specific.

                
> Minor Improvements related to balancer.
> ---------------------------------------
>
>                 Key: HBASE-5737
>                 URL: https://issues.apache.org/jira/browse/HBASE-5737
>             Project: HBase
>          Issue Type: Improvement
>          Components: master
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>            Priority: Minor
>         Attachments: HBASE-5737.patch
>
>
> Currently in Am.getAssignmentByTable()  we use a result map which is currenly a hashmap.
 It could be better if we have a treeMap.  Even in MetaReader.fullScan we have the treeMap
only so that we have the naming order maintained. I felt this change could be very useful
in cases where we are extending the DefaultLoadBalancer.  

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