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https://issues.apache.org/jira/browse/HBASE-7403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13537101#comment-13537101
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chunhui shen commented on HBASE-7403:
-------------------------------------
Thanks ted and ram
I upload the patch to review board
https://reviews.apache.org/r/8716/
> Online Merge
> ------------
>
> Key: HBASE-7403
> URL: https://issues.apache.org/jira/browse/HBASE-7403
> Project: HBase
> Issue Type: New Feature
> Affects Versions: 0.94.3
> Reporter: chunhui shen
> Assignee: chunhui shen
> Fix For: 0.96.0, 0.94.5
>
> Attachments: hbase-7403-94v1.patch, hbase-7403-trunkv1.patch, merge
> region.pdf
>
>
> We need merge in the following cases：
> 1.Region hole or region overlap, can’t be fix by hbck
> 2.Region become empty because of TTL and not reasonable Rowkey design
> 3.Region is always empty or very small because of presplit when create table
> 4.Too many empty or small regions would reduce the system performance(e.g.
> mslab)
> Current merge tools only support offline and are not able to redo if
> exception is thrown in the process of merging, causing a dirty data
> For online system, we need a online merge.
> This implement logic of this patch for Online Merge is :
> For example, merge regionA and regionB into regionC
> 1.Offline the two regions A and B
> 2.Merge the two regions in the HDFS(Create regionC’s directory, move
> regionA’s and regionB’s file to regionC’s directory, delete regionA’s and
> regionB’s directory)
> 3.Add the merged regionC to .META.
> 4.Assign the merged regionC
> As design of this patch , once we do the merge work in the HDFS,we could redo
> it until successful if it throws exception or abort or server restart, but
> couldn’t be rolled back.
> It depends on
> Use zookeeper to record the transaction journal state, make redo easier
> Use zookeeper to send/receive merge request
> Merge transaction is executed on the master
> Support calling merge request through API or shell tool
> About the merge process, please see the attachment and patch
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