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