HBASE-15124 Document the new 'normalization' feature in refguid
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Michael Stack
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@ -2704,4 +2704,140 @@ Viewing the Master log will give you insight on rsgroup operation.
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If it appears stuck, restart the Master process.
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If it appears stuck, restart the Master process.
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[[normalizer]]
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== Region Normalizer
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The Region Normalizer tries to make Regions all in a table about the same in size.
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It does this by finding a rough average. Any region that is larger than twice this
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size is split. Any region that is much smaller is merged into an adjacent region.
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It is good to run the Normalizer on occasion on a down time after the cluster has
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been running a while or say after a burst of activity such as a large delete.
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(The bulk of the below detail was copied wholesale from the blog by Romil Choksi at
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link:https://community.hortonworks.com/articles/54987/hbase-region-normalizer.html[HBase Region Normalizer])
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The Region Normalizer is feature available since HBase-1.2. It runs a set of
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pre-calculated merge/split actions to resize regions that are either too
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large or too small compared to the average region size for a given table. Region
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Normalizer when invoked computes a normalization 'plan' for all of the tables in
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HBase. System tables (such as hbase:meta, hbase:namespace, Phoenix system tables
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etc) and user tables with normalization disabled are ignored while computing the
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plan. For normalization enabled tables, normalization plan is carried out in
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parallel across multiple tables.
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Normalizer can be enabled or disabled globally for the entire cluster using the
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‘normalizer_switch’ command in the HBase shell. Normalization can also be
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controlled on a per table basis, which is disabled by default when a table is
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created. Normalization for a table can be enabled or disabled by setting the
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NORMALIZATION_ENABLED table attribute to true or false.
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To check normalizer status and enable/disable normalizer
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[source,bash]
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----
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hbase(main):001:0> normalizer_enabled
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true
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0 row(s) in 0.4870 seconds
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hbase(main):002:0> normalizer_switch false
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true
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0 row(s) in 0.0640 seconds
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hbase(main):003:0> normalizer_enabled
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false
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0 row(s) in 0.0120 seconds
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hbase(main):004:0> normalizer_switch true
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false
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0 row(s) in 0.0200 seconds
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hbase(main):005:0> normalizer_enabled
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true
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0 row(s) in 0.0090 seconds
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----
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When enabled, Normalizer is invoked in the background every 5 mins (by default),
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which can be configured using `hbase.normalization.period` in `hbase-site.xml`.
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Normalizer can also be invoked manually/programmatically at will using HBase shell’s
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`normalize` command. HBase by default uses `SimpleRegionNormalizer`, but users can
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design their own normalizer as long as they implement the RegionNormalizer Interface.
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Details about the logic used by `SimpleRegionNormalizer` to compute its normalization
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plan can be found link:https://hbase.apache.org/devapidocs/org/apache/hadoop/hbase/master/normalizer/SimpleRegionNormalizer.html[here].
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The below example shows a normalization plan being computed for an user table, and
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merge action being taken as a result of the normalization plan computed by SimpleRegionNormalizer.
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Consider an user table with some pre-split regions having 3 equally large regions
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(about 100K rows) and 1 relatively small region (about 25K rows). Following is the
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snippet from an hbase meta table scan showing each of the pre-split regions for
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the user table.
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----
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table_p8ddpd6q5z,,1469494305548.68b9892220865cb6048 column=info:regioninfo, timestamp=1469494306375, value={ENCODED => 68b9892220865cb604809c950d1adf48, NAME => 'table_p8ddpd6q5z,,1469494305548.68b989222 09c950d1adf48. 0865cb604809c950d1adf48.', STARTKEY => '', ENDKEY => '1'}
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....
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table_p8ddpd6q5z,1,1469494317178.867b77333bdc75a028 column=info:regioninfo, timestamp=1469494317848, value={ENCODED => 867b77333bdc75a028bb4c5e4b235f48, NAME => 'table_p8ddpd6q5z,1,1469494317178.867b7733 bb4c5e4b235f48. 3bdc75a028bb4c5e4b235f48.', STARTKEY => '1', ENDKEY => '3'}
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....
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table_p8ddpd6q5z,3,1469494328323.98f019a753425e7977 column=info:regioninfo, timestamp=1469494328486, value={ENCODED => 98f019a753425e7977ab8636e32deeeb, NAME => 'table_p8ddpd6q5z,3,1469494328323.98f019a7 ab8636e32deeeb. 53425e7977ab8636e32deeeb.', STARTKEY => '3', ENDKEY => '7'}
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....
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table_p8ddpd6q5z,7,1469494339662.94c64e748979ecbb16 column=info:regioninfo, timestamp=1469494339859, value={ENCODED => 94c64e748979ecbb166f6cc6550e25c6, NAME => 'table_p8ddpd6q5z,7,1469494339662.94c64e74 6f6cc6550e25c6. 8979ecbb166f6cc6550e25c6.', STARTKEY => '7', ENDKEY => '8'}
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....
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table_p8ddpd6q5z,8,1469494339662.6d2b3f5fd1595ab8e7 column=info:regioninfo, timestamp=1469494339859, value={ENCODED => 6d2b3f5fd1595ab8e7c031876057b1ee, NAME => 'table_p8ddpd6q5z,8,1469494339662.6d2b3f5f c031876057b1ee. d1595ab8e7c031876057b1ee.', STARTKEY => '8', ENDKEY => ''}
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----
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Invoking the normalizer using ‘normalize’ int the HBase shell, the below log snippet
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from HMaster log shows the normalization plan computed as per the logic defined for
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SimpleRegionNormalizer. Since the total region size (in MB) for the adjacent smallest
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regions in the table is less than the average region size, the normalizer computes a
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plan to merge these two regions.
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----
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2016-07-26 07:08:26,928 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] master.HMaster: Skipping normalization for table: hbase:namespace, as it's either system table or doesn't have auto
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normalization turned on
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2016-07-26 07:08:26,928 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] master.HMaster: Skipping normalization for table: hbase:backup, as it's either system table or doesn't have auto normalization turned on
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2016-07-26 07:08:26,928 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] master.HMaster: Skipping normalization for table: hbase:meta, as it's either system table or doesn't have auto normalization turned on
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2016-07-26 07:08:26,928 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] master.HMaster: Skipping normalization for table: table_h2osxu3wat, as it's either system table or doesn't have autonormalization turned on
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2016-07-26 07:08:26,928 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] normalizer.SimpleRegionNormalizer: Computing normalization plan for table: table_p8ddpd6q5z, number of regions: 5
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2016-07-26 07:08:26,929 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] normalizer.SimpleRegionNormalizer: Table table_p8ddpd6q5z, total aggregated regions size: 12
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2016-07-26 07:08:26,929 DEBUG [B.fifo.QRpcServer.handler=20,queue=2,port=20000] normalizer.SimpleRegionNormalizer: Table table_p8ddpd6q5z, average region size: 2.4
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2016-07-26 07:08:26,929 INFO [B.fifo.QRpcServer.handler=20,queue=2,port=20000] normalizer.SimpleRegionNormalizer: Table table_p8ddpd6q5z, small region size: 0 plus its neighbor size: 0, less thanthe avg size 2.4, merging them
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2016-07-26 07:08:26,971 INFO [B.fifo.QRpcServer.handler=20,queue=2,port=20000] normalizer.MergeNormalizationPlan: Executing merging normalization plan: MergeNormalizationPlan{firstRegion={ENCODED=> d51df2c58e9b525206b1325fd925a971, NAME => 'table_p8ddpd6q5z,,1469514755237.d51df2c58e9b525206b1325fd925a971.', STARTKEY => '', ENDKEY => '1'}, secondRegion={ENCODED => e69c6b25c7b9562d078d9ad3994f5330, NAME => 'table_p8ddpd6q5z,1,1469514767669.e69c6b25c7b9562d078d9ad3994f5330.',
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STARTKEY => '1', ENDKEY => '3'}}
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----
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Region normalizer as per it’s computed plan, merged the region with start key as ‘’
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and end key as ‘1’, with another region having start key as ‘1’ and end key as ‘3’.
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Now, that these regions have been merged we see a single new region with start key
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as ‘’ and end key as ‘3’
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----
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table_p8ddpd6q5z,,1469516907210.e06c9b83c4a252b130e column=info:mergeA, timestamp=1469516907431,
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value=PBUF\x08\xA5\xD9\x9E\xAF\xE2*\x12\x1B\x0A\x07default\x12\x10table_p8ddpd6q5z\x1A\x00"\x011(\x000\x00 ea74d246741ba. 8\x00
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table_p8ddpd6q5z,,1469516907210.e06c9b83c4a252b130e column=info:mergeB, timestamp=1469516907431,
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value=PBUF\x08\xB5\xBA\x9F\xAF\xE2*\x12\x1B\x0A\x07default\x12\x10table_p8ddpd6q5z\x1A\x011"\x013(\x000\x0 ea74d246741ba. 08\x00
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table_p8ddpd6q5z,,1469516907210.e06c9b83c4a252b130e column=info:regioninfo, timestamp=1469516907431, value={ENCODED => e06c9b83c4a252b130eea74d246741ba, NAME => 'table_p8ddpd6q5z,,1469516907210.e06c9b83c ea74d246741ba. 4a252b130eea74d246741ba.', STARTKEY => '', ENDKEY => '3'}
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....
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table_p8ddpd6q5z,3,1469514778736.bf024670a847c0adff column=info:regioninfo, timestamp=1469514779417, value={ENCODED => bf024670a847c0adffb74b2e13408b32, NAME => 'table_p8ddpd6q5z,3,1469514778736.bf024670 b74b2e13408b32. a847c0adffb74b2e13408b32.' STARTKEY => '3', ENDKEY => '7'}
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....
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table_p8ddpd6q5z,7,1469514790152.7c5a67bc755e649db2 column=info:regioninfo, timestamp=1469514790312, value={ENCODED => 7c5a67bc755e649db22f49af6270f1e1, NAME => 'table_p8ddpd6q5z,7,1469514790152.7c5a67bc 2f49af6270f1e1. 755e649db22f49af6270f1e1.', STARTKEY => '7', ENDKEY => '8'}
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....
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table_p8ddpd6q5z,8,1469514790152.58e7503cda69f98f47 column=info:regioninfo, timestamp=1469514790312, value={ENCODED => 58e7503cda69f98f4755178e74288c3a, NAME => 'table_p8ddpd6q5z,8,1469514790152.58e7503c 55178e74288c3a. da69f98f4755178e74288c3a.', STARTKEY => '8', ENDKEY => ''}
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----
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A similar example can be seen for an user table with 3 smaller regions and 1
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relatively large region. For this example, we have an user table with 1 large region containing 100K rows, and 3 relatively smaller regions with about 33K rows each. As seen from the normalization plan, since the larger region is more than twice the average region size it ends being split into two regions – one with start key as ‘1’ and end key as ‘154717’ and the other region with start key as '154717' and end key as ‘3’
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----
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] master.HMaster: Skipping normalization for table: hbase:backup, as it's either system table or doesn't have auto normalization turned on
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Computing normalization plan for table: table_p8ddpd6q5z, number of regions: 4
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Table table_p8ddpd6q5z, total aggregated regions size: 12
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Table table_p8ddpd6q5z, average region size: 3.0
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: No normalization needed, regions look good for table: table_p8ddpd6q5z
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Computing normalization plan for table: table_h2osxu3wat, number of regions: 5
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Table table_h2osxu3wat, total aggregated regions size: 7
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2016-07-26 07:39:45,636 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Table table_h2osxu3wat, average region size: 1.4
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2016-07-26 07:39:45,636 INFO [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SimpleRegionNormalizer: Table table_h2osxu3wat, large region table_h2osxu3wat,1,1469515926544.27f2fdbb2b6612ea163eb6b40753c3db. has size 4, more than twice avg size, splitting
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2016-07-26 07:39:45,640 INFO [B.fifo.QRpcServer.handler=7,queue=1,port=20000] normalizer.SplitNormalizationPlan: Executing splitting normalization plan: SplitNormalizationPlan{regionInfo={ENCODED => 27f2fdbb2b6612ea163eb6b40753c3db, NAME => 'table_h2osxu3wat,1,1469515926544.27f2fdbb2b6612ea163eb6b40753c3db.', STARTKEY => '1', ENDKEY => '3'}, splitPoint=null}
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2016-07-26 07:39:45,656 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] master.HMaster: Skipping normalization for table: hbase:namespace, as it's either system table or doesn't have auto normalization turned on
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2016-07-26 07:39:45,656 DEBUG [B.fifo.QRpcServer.handler=7,queue=1,port=20000] master.HMaster: Skipping normalization for table: hbase:meta, as it's either system table or doesn't
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have auto normalization turned on …..…..….
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2016-07-26 07:39:46,246 DEBUG [AM.ZK.Worker-pool2-t278] master.RegionStates: Onlined 54de97dae764b864504704c1c8d3674a on hbase-test-rc-5.openstacklocal,16020,1469419333913 {ENCODED => 54de97dae764b864504704c1c8d3674a, NAME => 'table_h2osxu3wat,1,1469518785661.54de97dae764b864504704c1c8d3674a.', STARTKEY => '1', ENDKEY => '154717'}
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2016-07-26 07:39:46,246 INFO [AM.ZK.Worker-pool2-t278] master.RegionStates: Transition {d6b5625df331cfec84dce4f1122c567f state=SPLITTING_NEW, ts=1469518786246, server=hbase-test-rc-5.openstacklocal,16020,1469419333913} to {d6b5625df331cfec84dce4f1122c567f state=OPEN, ts=1469518786246,
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server=hbase-test-rc-5.openstacklocal,16020,1469419333913}
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2016-07-26 07:39:46,246 DEBUG [AM.ZK.Worker-pool2-t278] master.RegionStates: Onlined d6b5625df331cfec84dce4f1122c567f on hbase-test-rc-5.openstacklocal,16020,1469419333913 {ENCODED => d6b5625df331cfec84dce4f1122c567f, NAME => 'table_h2osxu3wat,154717,1469518785661.d6b5625df331cfec84dce4f1122c567f.', STARTKEY => '154717', ENDKEY => '3'}
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----
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