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https://issues.apache.org/jira/browse/HBASE-24376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17116912#comment-17116912
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Huaxiang Sun commented on HBASE-24376:
--------------------------------------
Will post a backport for 2.2.
> MergeNormalizer is merging non-adjacent regions and causing region
> overlaps/holes.
> ----------------------------------------------------------------------------------
>
> Key: HBASE-24376
> URL: https://issues.apache.org/jira/browse/HBASE-24376
> Project: HBase
> Issue Type: Bug
> Components: master
> Affects Versions: 2.3.0
> Reporter: Huaxiang Sun
> Assignee: Huaxiang Sun
> Priority: Critical
> Fix For: 3.0.0-alpha-1, 2.3.0, 2.4.0
>
>
> Currently, we found normalizer was merging regions which are non-adjacent, it
> will cause inconsistencies in the cluster.
> {code:java}
> 439055 2020-05-08 17:47:09,814 INFO
> org.apache.hadoop.hbase.master.normalizer.MergeNormalizationPlan: Executing
> merging normalization plan: MergeNormalizationPlan{firstRegion={ENCODED =>
> 47fe236a5e3649ded95cb64ad0c08492, NAME =>
> 'TABLE,\x03\x01\x05\x01\x04\x02,1554838974870.47fe236a5e3649ded95cb64ad
> 0c08492.', STARTKEY => '\x03\x01\x05\x01\x04\x02', ENDKEY =>
> '\x03\x01\x05\x01\x04\x02\x01\x02\x02201904082200\x00\x00\x03Mac\x00\x00\x00\x00\x00\x00\x00\x00\x00iMac13,1\x00\x00\x00\x00\x00\x049.3-14E260\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x05'},
> secondRegion={ENCODED => 0c0f2aa67f4329d5c4 8ba0320f173d31, NAME =>
> 'TABLE,\x03\x01\x05\x02\x01\x01,1554830735526.0c0f2aa67f4329d5c48ba0320f173d31.',
> STARTKEY => '\x03\x01\x05\x02\x01\x01', ENDKEY =>
> '\x03\x01\x05\x02\x01\x02'}}
> 439056 2020-05-08 17:47:11,438 INFO org.apache.hadoop.hbase.ScheduledChore:
> CatalogJanitor-*****:16000 average execution time: 1676219193 ns.
> 439057 2020-05-08 17:47:11,730 INFO org.apache.hadoop.hbase.master.HMaster:
> Client=null/null merge regions [47fe236a5e3649ded95cb64ad0c08492],
> [0c0f2aa67f4329d5c48ba0320f173d31]
> {code}
>
> The root cause is that getMergeNormalizationPlan() uses a list of regionInfo
> which is ordered by regionName. regionName does not necessary guarantee the
> order of STARTKEY (let's say 'aa1', 'aa1!', in order of regionName, it will
> be 'aa1!' followed by 'aa1'. This will result in normalizer merging
> non-adjacent regions into one and creates overlaps. This is not an issue in
> branch-1 as the list is already ordered by RegionInfo.COMPARATOR in
> normalizer.
>
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