关于Hbase的预分区，解决热点问题

Hbase默认建表是只有一个分区的，开始的时候所有的数据都会查询这个分区，当这个分区达到一定大小的时候，就会进行做split操作；

因此为了确保regionserver的稳定和高效，应该尽量避免region分裂和热点的问题；

那么有的同学在做预分区的时候，可能是按照：

1）：

通过Hbase提供的api：
bin/hbase org.apache.hadoop.hbase.util.RegionSplitter demo1 HexStringSplit -c 10 -f info

默认建表是没有开启Bloomfilter和压缩参数的，这里为了提供读性能，建议开启Bloomfilter，同时使用压缩SNAPPY，进入hbase shell，首先需要disable 'poidb',然后使用使用 

alter 'poidb',{NAME => 'info',BLOOMFILTER => 'ROWCOL',COMPRESSION => 'SNAPPY',VERSIONS => '1'} 

-C 多少个分区
-f 列族

2）：

通过指定create命令

3）：

没做任何修饰的代码操作

package com.dongfeng.code.tools.writeDb

import com.dongfeng.code.tools.GlobalConfigUtils
import org.apache.hadoop.conf.Configuration
import org.apache.hadoop.hbase.{HBaseConfiguration, HColumnDescriptor, HTableDescriptor, TableName}
import org.apache.hadoop.hbase.client.{Admin, Connection, ConnectionFactory}
import org.apache.hadoop.hbase.util.Bytes

/**
  * Created by angel
  */
object WriteToHbaseDB {
  private val config: Configuration = HBaseConfiguration.create()
  config.set("hbase.zookeeper.quorum" , GlobalConfigUtils.hbaseQuorem)
  config.set("hbase.master" , GlobalConfigUtils.hbaseMaster)
  config.set("hbase.zookeeper.property.clientPort" , GlobalConfigUtils.clientPort)
  config.set("hbase.rpc.timeout" , GlobalConfigUtils.rpcTimeout)
  config.set("hbase.client.operator.timeout" , GlobalConfigUtils.operatorTimeout)
  //def scannTimeout = conf.getString("c")
  config.set("hbase.client.scanner.timeout.period" , GlobalConfigUtils.scannTimeout)
  private val conn: Connection = ConnectionFactory.createConnection(config)
  private val admin: Admin = conn.getAdmin
  //创建表
  def createTable(tableName:TableName, columnFamily:String) = {

    val hTableDescriptor = new HTableDescriptor(tableName)
    val hColumnDescriptor = new HColumnDescriptor(columnFamily)
    hTableDescriptor.addFamily(hColumnDescriptor)
    //如果表不存在则创建表
    if(!admin.tableExists(tableName)){
      var splitKeys: List[Array[Byte]] = List(
        Bytes.toBytes("40000") ,
        Bytes.toBytes("80000") ,
        Bytes.toBytes("120000") ,
        Bytes.toBytes("160000")
      )
//      for (x <- 1 to 5) {
//        if(x<10){
//          splitKeys = splitKeys.+:(Bytes.toBytes(x.toString))
//        }else{
//          splitKeys = splitKeys.+:(Bytes.toBytes(x.toString))
//        }
//      }
      try{
        //创建表
        admin.createTable(hTableDescriptor, splitKeys.toArray)
      }finally {
        admin.close()
      }
    }
  }

  def main(args: Array[String]): Unit = {
    createTable(TableName.valueOf("demo3") , "info")
  }
}

其实上面的这些操作，会无形中限制我们的rowkey的最初设计，既要考虑高效的字典排列方式，还要考虑热点问题。往往稍微有点偏差，就会出现大部分的数据都往一个region中跑，显然不合理

因此，我觉得至少在我的业务中是需要进行rowkey的加盐或者MD5操作的，达到rowkey的散列

我这里进行MD5加密处理

package com.df.tools

import java.util.concurrent.atomic.AtomicInteger

import com.df.Contant.GlobalConfigUtils
import org.apache.hadoop.conf.Configuration
import org.apache.hadoop.hbase._
import org.apache.hadoop.hbase.client._
import org.apache.hadoop.hbase.io.compress.Compression.Algorithm
import org.apache.hadoop.hbase.protobuf.ProtobufUtil
import org.apache.hadoop.hbase.util.{Base64, Bytes, MD5Hash}
import org.apache.hadoop.hbase.util.RegionSplitter.HexStringSplit

/**
  * Created by angel
  */
object HbaseTools {
  private val config: Configuration = HBaseConfiguration.create()
  config.set("hbase.zookeeper.quorum" , GlobalConfigUtils.hbaseQuorem)
  config.set("hbase.master" , GlobalConfigUtils.hbaseMaster)
  config.set("hbase.zookeeper.property.clientPort" , GlobalConfigUtils.clientPort)
  config.set("hbase.rpc.timeout" , GlobalConfigUtils.rpcTimeout)
  config.set("hbase.client.operator.timeout" , GlobalConfigUtils.operatorTimeout)
  config.set("hbase.client.scanner.timeout.period" , GlobalConfigUtils.scannTimeout)
  private val conn: Connection = ConnectionFactory.createConnection(config)
  private val admin: Admin = conn.getAdmin
  val atomic = new AtomicInteger(0)
  var resultAtomic = 0
  /**
    * @return 构建表的连接
    * */
  def Init(tableName: String , columnFamily:String):Table = {
    val hTableDescriptor = new HTableDescriptor(TableName.valueOf(tableName))
    val hColumnDescriptor = new HColumnDescriptor(columnFamily)
    hTableDescriptor.addFamily(hColumnDescriptor)
    if(!admin.tableExists(TableName.valueOf(tableName))){
//      admin.createTable(hTableDescriptor)
      createHTable(conn , tableName , 10 , Array(columnFamily))

    }
    conn.getTable(TableName.valueOf(tableName))
  }

  // 对指定的列构造rowKey,采用Hash前缀拼接业务主键的方法
  def rowKeyWithHashPrefix(column: String*): Array[Byte] = {
    val rkString = column.mkString("")
    val hash_prefix = getHashCode(rkString)
    val rowKey = Bytes.add(Bytes.toBytes(hash_prefix), Bytes.toBytes(rkString))
    rowKey
  }

  // 对指定的列构造rowKey, 采用Md5 前缀拼接业务主键方法，主要目的是建表时采用MD5 前缀进行预分区
  def rowKeyWithMD5Prefix(separator:String,length: Int,column: String*): Array[Byte] = {
    val columns = column.mkString(separator)

    var md5_prefix = MD5Hash.getMD5AsHex(Bytes.toBytes(columns))
    if (length < 8){
      md5_prefix = md5_prefix.substring(0, 8)
    }else if (length >= 8 || length <= 32){
      md5_prefix = md5_prefix.substring(0, length)
    }
    val row = Array(md5_prefix,columns)
    val rowKey = Bytes.toBytes(row.mkString(separator))
    rowKey
  }

  // 对指定的列构造RowKey,采用MD5方法
  def rowKeyByMD5(column: String*): Array[Byte] = {
    val rkString = column.mkString("")
    val md5 = MD5Hash.getMD5AsHex(Bytes.toBytes(rkString))
    val rowKey = Bytes.toBytes(md5)
    rowKey
  }
  // 直接拼接业务主键构造rowKey
  def rowKey(column:String*):Array[Byte] = Bytes.toBytes(column.mkString(""))

  // Hash 前缀的方法：指定列拼接之后与最大的Short值做 & 运算
  // 目的是预分区，尽量保证数据均匀分布
  private def getHashCode(field: String): Short ={
    (field.hashCode() & 0x7FFF).toShort
  }

  /**
    * @param tablename 表名
    * @param regionNum 预分区数量
    * @param columns 列簇数组
    */
  def createHTable(connection: Connection, tablename: String,regionNum: Int, columns: Array[String]): Unit = {

    val nameSpace = "df"
    val hexsplit: HexStringSplit = new HexStringSplit()
    // 预先构建分区，指定分区的start key
    val splitkeys: Array[Array[Byte]] = hexsplit.split(regionNum)

    val admin = connection.getAdmin

    val tableName = TableName.valueOf(tablename)

    if (!admin.tableExists(tableName)) {
      val tableDescriptor = new HTableDescriptor(tableName)

      if (columns != null) {
        columns.foreach(c => {
          val hcd = new HColumnDescriptor(c.getBytes()) //设置列簇
          hcd.setMaxVersions(1)
          hcd.setCompressionType(Algorithm.SNAPPY) //设定数据存储的压缩类型.默认无压缩(NONE)
          tableDescriptor.addFamily(hcd)
        })
      }
      admin.createTable(tableDescriptor,splitkeys)
    }

  }

  /**
    * @param tableName
    * @param key
    * @param columnFamily
    * @param column
    * @param data 要落地的数据
    * */
  def putData(tableName: String , key:String , columnFamily:String , column:String , data:String):Int = {
    val table: Table = Init(tableName , columnFamily)
    try{
      val rowkey = HbaseTools.rowKeyByMD5(key)
      val put: Put = new Put(rowkey)
      put.addColumn(Bytes.toBytes(columnFamily) ,Bytes.toBytes(column.toString) , Bytes.toBytes(data.toString))
      table.put(put)
      resultAtomic = atomic.incrementAndGet()
    }catch{
      case e:Exception => e.printStackTrace()
        resultAtomic = atomic.decrementAndGet()
    }finally {
      table.close()
    }
    resultAtomic
  }

  /**
    * @param mapData 要插入的数据[列明 ， 值]
    * */

  def putMapData(tableName: String , columnFamily:String, key:String  , mapData:Map[String , String]):Int = {
    val table: Table = Init(tableName , columnFamily)
    try{
      //TODO rowKeyWithMD5Prefix
      val rowkey = HbaseTools.rowKeyByMD5(key)
      val put: Put = new Put(rowkey)
      if(mapData.size > 0){
        for((k , v) <- mapData){
          put.addColumn(Bytes.toBytes(columnFamily) ,Bytes.toBytes(k.toString) , Bytes.toBytes(v.toString))
        }
      }
      table.put(put)
      resultAtomic = atomic.incrementAndGet()
    }catch{
      case e:Exception => e.printStackTrace()
        resultAtomic = atomic.decrementAndGet()
    }finally {
      table.close()
    }
    resultAtomic
  }

  def deleteData(tableName: String , rowKey:String , columnFamily:String):Int ={
    val table: Table = Init(tableName , columnFamily)
    try{
      val delete = new Delete(Bytes.toBytes(rowKey))
      table.delete(delete)
      resultAtomic = atomic.decrementAndGet()
    }catch{
      case e:Exception => e.printStackTrace()
        resultAtomic = atomic.decrementAndGet()
    }finally {
      table.close()
    }
    resultAtomic
  }

  def convertScanToString(scan: Scan):String={
    val proto = ProtobufUtil.toScan(scan)
    return Base64.encodeBytes(proto.toByteArray)
  }
}