HBase - MapReduce - HBase 作为输入源的示例 | 那伊抹微笑

博文作者：那伊抹微笑

csdn 博客地址：http://blog.csdn.net/u012185296

itdog8 地址链接 : http://www.itdog8.com/thread-203-1-1.html

博文标题：HBase - MapReduce - HBase 作为输入源的示例 | 那伊抹微笑

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参考 : http://abloz.com/hbase/book.html#mapreduce.example

1 官网代码

下面是使用HBase 作为源的MapReduce读取示例。特别是仅有Mapper实例，没有Reducer。Mapper什么也不产生。

如下所示...

Configuration config = HBaseConfiguration.create();Job job = new Job(config, "ExampleRead");job.setJarByClass(MyReadJob.class);     // class that contains mapper

Scan scan = new Scan();scan.setCaching(500);        // 1 is the default in Scan, which will be bad for MapReduce jobsscan.setCacheBlocks(false);  // don‘t set to true for MR jobs// set other scan attrs...

TableMapReduceUtil.initTableMapperJob(  tableName,        // input HBase table name  scan,             // Scan instance to control CF and attribute selection  MyMapper.class,   // mapper  null,             // mapper output key   null,             // mapper output value  job);job.setOutputFormatClass(NullOutputFormat.class);   // because we aren‘t emitting anything from mapper

boolean b = job.waitForCompletion(true);if (!b) {  throw new IOException("error with job!");}

...mapper需要继承于TableMapper...

public class MyMapper extends TableMapper<Text, LongWritable> {
public void map(ImmutableBytesWritable row, Result value, Context context)
throws InterruptedException, IOException {
// process data for the row from the Result instance.

2 我的参考代码

package com.itdog8.cloud.hbase.mr.test;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

/**
 * TestHBaseAsSourceMapReduceMainClass
 *
 * @author 那伊抹微笑
 * @date 2015-07-30 18:00:21
 *
 */
public class TestHBaseAsSourceMapReduceMainClass {
 private static final Log _log = LogFactory.getLog(TestHBaseAsSourceMapReduceMainClass.class);

 private static final String JOB_NAME = "TestHBaseAsSourceMapReduce";
 private static String tmpPath = "/tmp/com/itdog8/yting/TestHBaseAsSourceMapReduce";
 private static String hbaseInputTble = "itdog8:test_1";

 public static class ExampleSourceMapper extends TableMapper<Text, Text> {
  private Text k = new Text();
  private Text v = new Text();

  @Override
  protected void setup(Context context) throws IOException, InterruptedException {
   super.setup(context);
  }

  @Override
  protected void map(ImmutableBytesWritable key, Result value, Context context) throws IOException, InterruptedException {
   String rowkey = Bytes.toString(key.get());

   // 这里的操作需要熟悉下 Result 的操作就行了，接下来就是业务逻辑了
   try {

    // set value
    k.set("望咩望");
    v.set("食屎啦你");

    // context write to reducer
    context.write(k, v);
   } catch (Exception e) {
    e.printStackTrace();
   }
  }

  @Override
  protected void cleanup(Context context) throws IOException, InterruptedException {
   super.cleanup(context);
  }

 }

 public static void main(String[] args) throws Exception {
  // hbase configuration
  Configuration conf = HBaseConfiguration.create();
  conf.set("hbase.zookeeper.quorum", "a234-198.hadoop.com,a234-197.hadoop.com,a234-196.hadoop.com");
  conf.set("hbase.zookeeper.property.clientPort", "2181");

  // batch and caching
  Scan scan = new Scan();
  scan.setCaching(10000);
  scan.setCacheBlocks(false);
  scan.setMaxVersions(1);

  // set hadoop speculative execution to false
  conf.setBoolean("mapred.map.tasks.speculative.execution", false);
  conf.setBoolean("mapred.reduce.tasks.speculative.execution", false);

  // tmp index path
  tmpPath = args[0];
  Path tmpIndexPath = new Path(tmpPath);
  FileSystem fs = FileSystem.get(conf);
  if(fs.exists(tmpIndexPath)) {
//	 fs.delete(tmpIndexPath, true); // dangerous
//	 _log.info("delete tmp index path : " + tmpIndexPath.getName());
   _log.warn("The hdfs path ["+tmpPath+"] existed, please change a path.");
   return ;
  }

  // Job && conf
  Job job = new Job(conf, JOB_NAME);
  job.setJarByClass(TestHBaseAsSourceMapReduceMainClass.class);

  TableMapReduceUtil.initTableMapperJob(hbaseInputTble, scan, ExampleSourceMapper.class, Text.class, Text.class, job);
//	 job.setReducerClass(MyReducer.class); // 自己的处理逻辑
  job.setOutputKeyClass(Text.class);
  job.setOutputValueClass(Text.class);
  job.setOutputFormatClass(TextOutputFormat.class);
  FileOutputFormat.setOutputPath(job, tmpIndexPath);

  int success = job.waitForCompletion(true) ? 0 : 1;

  System.exit(success);
 }
}

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