环境：cdh5.1.0

启用协处理器方法1.

启用协处理器 Aggregation(Enable Coprocessor Aggregation)
我们有两个方法：1.启动全局aggregation，能过操纵所有的表上的数据。通过修改hbase-site.xml这个文件来实现，只需要添加如下代码：

<property>
   <name>hbase.coprocessor.user.region.classes</name>
   <value>org.apache.hadoop.hbase.coprocessor.AggregateImplementation</value>
 </property>

启用协处理器方法2.

启用表aggregation，只对特定的表生效。通过HBase Shell 来实现。


(1)disable指定表。hbase> disable ‘mytable‘


(2)添加aggregation hbase> alter ‘mytable‘, METHOD => ‘table_att‘,‘coprocessor‘=>‘|org.apache.hadoop.hbase.coprocessor.AggregateImplementation||‘


(3)重启指定表 hbase> enable ‘mytable‘

代码：

package com.jamesfen.hbase;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.client.coprocessor.AggregationClient;
import org.apache.hadoop.hbase.client.coprocessor.LongColumnInterpreter;
import org.apache.hadoop.hbase.coprocessor.ColumnInterpreter;
import org.apache.hadoop.hbase.util.Bytes;

public class MyAggregationClient {

	private static final byte[] TABLE_NAME = Bytes.toBytes("bigtable1w");
	private static final byte[] CF = Bytes.toBytes("bd");
	public static void main(String[] args) throws Throwable {
	Configuration customConf = new Configuration();
	customConf.set("hbase.zookeeper.quorum",
	"192.168.58.101");
	//提高RPC通信时长
	customConf.setLong("hbase.rpc.timeout", 600000);
	//设置Scan缓存
	customConf.setLong("hbase.client.scanner.caching", 1000);
	Configuration configuration = HBaseConfiguration.create(customConf);
	AggregationClient aggregationClient = new AggregationClient(
	configuration);
	Scan scan = new Scan();
	//指定扫描列族，唯一值
	scan.addFamily(CF);
	//long rowCount = aggregationClient.rowCount(TABLE_NAME, null, scan);
	long rowCount = aggregationClient.rowCount(TableName.valueOf("bigtable1w"), new LongColumnInterpreter(), scan);
	System.out.println("row count is " + rowCount);

	}
	


}

HBase 协处理器统计行数