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ramkrishna.s.vasudevan commented on HBASE-7403: ----------------------------------------------- I have gone thro the code at high level. One doubt is regarding the prepare() method. {code} if (regionA.isSplit() || regionA.isOffline()) { + available = false; + LOG.debug("Region " + regionA.getRegionNameAsString() + + " is split or offline"); + } else if (regionB.isSplit() || regionB.isOffline()) { + available = false; + LOG.debug("Region " + regionB.getRegionNameAsString() + + " is split or offline"); ............... {code} Should these 'elseifs' all be 'ifs'. Because even if RegionB is not available we should not be able to merge right? > 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: 7403-trunkv5.patch, hbase-7403-94v1.patch, > hbase-7403-trunkv1.patch, hbase-7403-trunkv5.patch, hbase-7403-trunkv5.patch, > merge region.pdf > > > The feature of this online merge: > 1.Online,no necessary to disable table > 2.Less change for current code, could applied in trunk,0.94 or 0.92,0.90 > 3.Easy to call merege request, no need to input a long region name, only > encoded name enough > 4.No limit when operation, you don't need to care event like Server Dead, > Balance, Split, Disabing/Enabing table, no need to care whether you send a > wrong merge request, it alread have done for you > 5.Only little offline time for two merging regions > 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 -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira