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https://issues.apache.org/jira/browse/HBASE-10576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14122708#comment-14122708
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rajeshbabu commented on HBASE-10576:
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[~stack]
bq. How is this balancer patch supposed to work?
Once this shadow region feature goes in the balancer patch is not required.
We can ensure the co-location using coprocessors.
bq. I turn on this feature for a table? Or is it for whole cluster?
It's region wise Stack. The shadow region is like offline region but not
completely
(Offline at master side and can be opened/closed at region server through
coprocessors).
If we make a region shadow then master considers it as offline and will not
move/reassign
in any case like master/RS failover. At the same time the region serves reads
and writes
from external client if it's online at RS.
In case of secondary index,to ensure co-location we can make the index
region(s) shadow
and open/close while opening/closing data region(s) through coprocessors.
Since the regions cannot be moved by master they will be served by the RS
holding data region always.
The shadow region operation can be performed similar like split or merge on a
region.
If we want to make the table shadow we need to make all the regions shadow.
Thanks.
> Custom load balancer to co-locate the regions of two tables which are having
> same split keys
> --------------------------------------------------------------------------------------------
>
> Key: HBASE-10576
> URL: https://issues.apache.org/jira/browse/HBASE-10576
> Project: HBase
> Issue Type: Sub-task
> Components: Balancer
> Reporter: rajeshbabu
> Assignee: rajeshbabu
> Attachments: HBASE-10536_v2.patch, HBASE-10576.patch,
> HBASE-10576_shadow_regions_wip.patch
>
>
> To support local indexing both user table and index table should have same
> split keys. This issue to provide custom balancer to colocate the regions of
> two tables which are having same split keys.
> This helps in Phoenix as well.
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