hbase Normalizer解决预分区错误，在不动数据的情况下完美解决热点问题
about云论坛很多会员，遇到hbase已经预分区完毕，在装上数据之后，发现并不是很合理，有的分区数据多，有的数据很少。想重新划分分区。这在以前的版本是非常的困难的，解决办法只有重新创建建表，然后重新导数据，这是非常麻烦的，特别是数据量已经非常大。hbase为了解决这个问题，增加了Normalizer这个功能.
Region Normalizer使用表的所有region大致相同大小。它通过找到一个粗略的平均值来做到这一点。大于这个平均值【size】的两倍的region将会被分割。更小的region将会合并到相邻的region。
在集群空闲的时候，或则比较大的改动后比如大量删除，适合运行Normalizer 。自HBase-1.2开始，Region Normalizer便具有功能。它运行一组预先计算的merge/split操作，以调整比table的平均region太大或太小区region。Region Normalizer为hbase所有表调用计算‘plan’。系统表（比如 hbase:meta, hbase:namespace, Phoenix 系统等）和用户表当计算‘plan’时，禁用Normalizer会被忽略。对于启用了normalization的表，normalization plan跨多个表并行执行。
可以使用HBase shell中的'normalizer_switch'命令在整个集群中全局启用或禁用Normalizer。Normalization 也可以在每一个表基础上进行控制，默认情况下创建表时禁用此操作。通过将NORMALIZATION_ENABLED表属性设置为true或false，可以启用或禁用表的Normalization。
检测normalizer状态和enable/disable normalizer
hbase(main):001:0> normalizer_enabled true 0 row(s) in 0.4870 seconds hbase(main):002:0> normalizer_switch false true 0 row(s) in 0.0640 seconds hbase(main):003:0> normalizer_enabled false 0 row(s) in 0.0120 seconds hbase(main):004:0> normalizer_switch true false 0 row(s) in 0.0200 seconds hbase(main):005:0> normalizer_enabled true 0 row(s) in 0.0090 seconds
启用时，每5分钟在后台调用Normalizer（默认情况下），可以在hbase-site.xml中配置hbase.normalization.period时间。Normalizer也可以使用HBase shell的normalize命令手动/编程调用。HBase默认使用SimpleRegionNormalizer，但只要用户实现RegionNormalizer接口，用户就可以继承RegionNormalizer接口设计自己的normalizer 。有关SimpleRegionNormalizer用于计算normalization plan的逻辑的详细信息，请参阅此处(https://hbase.apache.org/devapid ... gionNormalizer.html)。截图如下
下面展示了为用户表计算的normalization plan，合并操作由SimpleRegionNormalizer采取的计算规范化计划（normalization plan ）。
假如一个具有一些预分割区域的用户表，其具有3个同样大的region（大约100K行）和1个相对小的区域（大约25K行）。 以下是hbase meta表扫描的部分，显示用户表的每个预分割regions 。
table_p8ddpd6q5z,,1469494305548.68b9892220865cb6048 column=info:regioninfo, timestamp=1469494306375, value={ENCODED => 68b9892220865cb604809c950d1adf48, NAME => 'table_p8ddpd6q5z,,1469494305548.68b989222 09c950d1adf48. 0865cb604809c950d1adf48.', STARTKEY => '', ENDKEY => '1'} .... 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'} .... 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'} .... 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'} .... table_p8ddpd6q5z,8,1469494339662.6d2b3f5fd1595ab8e7 column=info:regioninfo, timestamp=1469494339859, value={ENCODED => 6d2b3f5fd1595ab8e7c031876057b1ee, NAME => 'table_p8ddpd6q5z,8,1469494339662.6d2b3f5f c031876057b1ee. d1595ab8e7c031876057b1ee.', STARTKEY => '8', ENDKEY => ''}
在HBase shell中使用'normalize'调用标准化程序（normalizer ），HMaster日志中的以下日志片段显示按照为SimpleRegionNormalizer定义的逻辑计算的标准化计划（normalization plan）。 由于表中相邻最小区域的总区域大小（以MB为单位）小于平均区域，因此规范器计算（ normalizer computes）合并这两个区域的计划。
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 normalization turned on 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 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 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 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 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 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 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 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.', STARTKEY => '1', ENDKEY => '3'}}
Region normalizer按照计算计划，合并start key作为‘’，和end key为'1'的region。另外一个region，start key为‘1’，end key为‘3’，现在这两个region合并为一个新的region，start key 为‘’ 和end key 为‘3’
table_p8ddpd6q5z,,1469516907210.e06c9b83c4a252b130e column=info:mergeA, timestamp=1469516907431, value=PBUF\x08\xA5\xD9\x9E\xAF\xE2*\x12\x1B\x0A\x07default\x12\x10table_p8ddpd6q5z\x1A\x00"\x011(\x000\x00 ea74d246741ba. 8\x00 table_p8ddpd6q5z,,1469516907210.e06c9b83c4a252b130e column=info:mergeB, timestamp=1469516907431, value=PBUF\x08\xB5\xBA\x9F\xAF\xE2*\x12\x1B\x0A\x07default\x12\x10table_p8ddpd6q5z\x1A\x011"\x013(\x000\x0 ea74d246741ba. 08\x00 table_p8ddpd6q5z,,1469516907210.e06c9b83c4a252b130e column=info:regioninfo, timestamp=1469516907431, value={ENCODED => e06c9b83c4a252b130eea74d246741ba, NAME => 'table_p8ddpd6q5z,,1469516907210.e06c9b83c ea74d246741ba. 4a252b130eea74d246741ba.', STARTKEY => '', ENDKEY => '3'} .... 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'} .... 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'} .... table_p8ddpd6q5z,8,1469514790152.58e7503cda69f98f47 column=info:regioninfo, timestamp=1469514790312, value={ENCODED => 58e7503cda69f98f4755178e74288c3a, NAME => 'table_p8ddpd6q5z,8,1469514790152.58e7503c 55178e74288c3a. da69f98f4755178e74288c3a.', STARTKEY => '8', ENDKEY => ''}
对于具有3个较小region和1个较大region的用户表可以看到类似的例子。 在这个例子中，我们有一个用户表，其中一个大region包含100K行，另外三个region相对较小，每个region大约有33K行。 从规范化计划中（ normalization plan）可以看出，由于较大的region是平均region大小的两倍以上，所以它们分割成两个region - 一个以start key为'1'，end key为'154717'，另一个区域的start key为 '154717'和end key为'3'
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 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 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 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 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 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 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 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 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 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} 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 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 have auto normalization turned on …..…..…. 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'} 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, server=hbase-test-rc-5.openstacklocal,16020,1469419333913} 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'}
