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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HBASE-6331) Problem with HBCK mergeOverlaps
Date Thu, 05 Jul 2012 09:33:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13406934#comment-13406934
] 

ramkrishna.s.vasudevan edited comment on HBASE-6331 at 7/5/12 9:33 AM:
-----------------------------------------------------------------------

This issue we observed after doing -fixSplitParents..followed by hbck -fix and hbck -repair.
 I think we may need documentation here on the usage of fixSplitParents.
Parent region A got split into A1 and A2.

A -> startkey = 'x' and endkey = ''.

So A1 -> startkey = 'x' and endkey = 'x1'
A2 -> startkey = 'x1' and endkey =''.


Here while reading the hdfs hbck finds there are 2 regions with same start key and 1 region
that overlaps.
{code}
ERROR: (region ufdr,010193811093051,1341438516341.cd3d13f6574059498ceded9661e136cd.) Multiple
regions have the same startkey: 010193811093051
ERROR: (region ufdr,010193811093051,1341438202996.e3af982dffd49d785f76ab6e5aa36fc0.) Multiple
regions have the same startkey: 010193811093051
ERROR: (regions ufdr,010193811093051,1341438202996.e3af982dffd49d785f76ab6e5aa36fc0. and ufdr,010196915311117,1341438516341.865326e49dfa71996a92dfa5e45c6977.)
There is an overlap in the region chain.
{code}
{code}
12/07/05 11:14:09 DEBUG util.HBaseFsck: HRegionInfo read: {NAME => 'ufdr,010193811093051,1341438516341.cd3d13f6574059498ceded9661e136cd.',
STARTKEY => '010193811093051', ENDKEY => '010196915311117', ENCODED => cd3d13f6574059498ceded9661e136cd,}
12/07/05 11:14:09 DEBUG util.HBaseFsck: HRegionInfo read: {NAME => 'ufdr,010193811093051,1341438202996.e3af982dffd49d785f76ab6e5aa36fc0.',
STARTKEY => '010193811093051', ENDKEY => '', ENCODED => e3af982dffd49d785f76ab6e5aa36fc0,}
12/07/05 11:14:09 DEBUG util.HBaseFsck: HRegionInfo read: {NAME => 'ufdr,010196915311117,1341438516341.865326e49dfa71996a92dfa5e45c6977.',
STARTKEY => '010196915311117', ENDKEY => '', ENCODED => 865326e49dfa71996a92dfa5e45c6977,}
{code}
Now finally while fixing this HBCK creates a region which does not have empty start key.
We can try fixing HBASE-6223 so that we are clear on the usage of -fixSplitParents.

                
      was (Author: ram_krish):
    This issue we observed after doing -fixSplitParents..followed by hbck -fix and hbck -repair.
 I think we may need documentation here on the usage of fixSplitParents.
Parent region A got split into A1 and A2.

A -> startkey = 'x' and endkey = ''.

So A1 -> startkey = 'x' and endkey = 'x1'
A2 -> startkey = 'x1' and endkey =''.


Here while reading the hdfs hbck finds there are 2 regions with same start key and 1 region
that overlaps.
{code}
ERROR: (region ufdr,010193811093051,1341438516341.cd3d13f6574059498ceded9661e136cd.) Multiple
regions have the same startkey: 010193811093051
ERROR: (region ufdr,010193811093051,1341438202996.e3af982dffd49d785f76ab6e5aa36fc0.) Multiple
regions have the same startkey: 010193811093051
ERROR: (regions ufdr,010193811093051,1341438202996.e3af982dffd49d785f76ab6e5aa36fc0. and ufdr,010196915311117,1341438516341.865326e49dfa71996a92dfa5e45c6977.)
There is an overlap in the region chain.
{code}
12/07/05 11:14:09 DEBUG util.HBaseFsck: HRegionInfo read: {NAME => 'ufdr,010193811093051,1341438516341.cd3d13f6574059498ceded9661e136cd.',
STARTKEY => '010193811093051', ENDKEY => '010196915311117', ENCODED => cd3d13f6574059498ceded9661e136cd,}
12/07/05 11:14:09 DEBUG util.HBaseFsck: HRegionInfo read: {NAME => 'ufdr,010193811093051,1341438202996.e3af982dffd49d785f76ab6e5aa36fc0.',
STARTKEY => '010193811093051', ENDKEY => '', ENCODED => e3af982dffd49d785f76ab6e5aa36fc0,}
12/07/05 11:14:09 DEBUG util.HBaseFsck: HRegionInfo read: {NAME => 'ufdr,010196915311117,1341438516341.865326e49dfa71996a92dfa5e45c6977.',
STARTKEY => '010196915311117', ENDKEY => '', ENCODED => 865326e49dfa71996a92dfa5e45c6977,}
{code}
Now finally while fixing this HBCK creates a region which does not have empty start key.
We can try fixing HBASE-6223 so that we are clear on the usage of -fixSplitParents.

                  
> Problem with HBCK mergeOverlaps
> -------------------------------
>
>                 Key: HBASE-6331
>                 URL: https://issues.apache.org/jira/browse/HBASE-6331
>             Project: HBase
>          Issue Type: Bug
>          Components: hbck
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 0.96.0, 0.94.1
>
>         Attachments: HBASE-6331_94.patch, HBASE-6331_Trunk.patch
>
>
> In HDFSIntegrityFixer#mergeOverlaps(), there is a logic to create the final range of
the region after the overlap.
> I can see one issue with this code
> {code}
>             if (RegionSplitCalculator.BYTES_COMPARATOR
>                     .compare(hi.getEndKey(), range.getSecond()) > 0) {
>               range.setSecond(hi.getEndKey());
>             }
> {code}
> Here suppose the regions include the end region for which the endKey will be empty, we
need to get finally the range with endkey as empty byte[]
> But as per the above logic it will see that any other key greater than the empty byte[]
and will set it.
> Finally the new region created will not get endkey as empty byte[]

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