Question

我是hadoop的新手。我有一个MapReduce作业，应该从Hdfs获取输入并将reducer的输出写入Hbase。我没有找到任何好的例子。

这是代码，运行此示例的错误是map中的Type mismatch，期望ImmutableBytesWritable收到IntWritable。

Mapper类

public static class AddValueMapper extends Mapper < LongWritable,
 Text, ImmutableBytesWritable, IntWritable > {  

  /* input <key, line number : value, full line>
   *  output <key, log key : value >*/  
public void map(LongWritable key, Text value, 
     Context context)throws IOException, 
     InterruptedException {
  byte[] key;
  int value, pos = 0;
  String line = value.toString();
  String p1 , p2 = null;
  pos = line.indexOf("=");

   //Key part
   p1 = line.substring(0, pos);
   p1 = p1.trim();
   key = Bytes.toBytes(p1);   

   //Value part
   p2 = line.substring(pos +1);
   p2 = p2.trim();
   value = Integer.parseInt(p2);

   context.write(new ImmutableBytesWritable(key),new IntWritable(value));
  }
}

减速机等级

public static class AddValuesReducer extends TableReducer<
  ImmutableBytesWritable, IntWritable, ImmutableBytesWritable> {

  public void reduce(ImmutableBytesWritable key, Iterable<IntWritable> values, 
   Context context) throws IOException, InterruptedException {

         long total =0;
         // Loop values
         while(values.iterator().hasNext()){
           total += values.iterator().next().get();
         }
         // Put to HBase
         Put put = new Put(key.get());
         put.add(Bytes.toBytes("data"), Bytes.toBytes("total"),
           Bytes.toBytes(total));
         Bytes.toInt(key.get()), total));
            context.write(key, put);
        }
    }

我的HDFS工作类似，工作正常。

编辑于18-06-2013 。大学项目两年前成功完成。对于作业配置（驱动程序部分），请检查正确答案。

Answer 1

以下是解决问题的代码

驱动程序

HBaseConfiguration conf =  HBaseConfiguration.create();
Job job = new Job(conf,"JOB_NAME");
    job.setJarByClass(yourclass.class);
    job.setMapperClass(yourMapper.class);
    job.setMapOutputKeyClass(Text.class);
    job.setMapOutputValueClass(Intwritable.class);
    FileInputFormat.setInputPaths(job, new Path(inputPath));
    TableMapReduceUtil.initTableReducerJob(TABLE,
            yourReducer.class, job);
    job.setReducerClass(yourReducer.class);
            job.waitForCompletion(true);

映射器安培;减速

class yourMapper extends Mapper<LongWritable, Text, Text,IntWritable> {
//@overide map()
 }

class yourReducer
        extends
        TableReducer<Text, IntWritable, 
        ImmutableBytesWritable>
{
//@override reduce()
}

Answer 2

不确定为什么HDFS版本有效：通常你必须设置作业的输入格式，而FileInputFormat是一个抽象类。也许你留下了一些线？比如

job.setInputFormatClass(TextInputFormat.class);

Answer 3

HBase中BulkLoad数据的最佳和最快方式是使用HFileOutputFormat和CompliteBulkLoad实用程序。

您会找到示例代码here：

希望这会有用：）

Answer 4

 public void map(LongWritable key, Text value, 
 Context context)throws IOException, 
 InterruptedException {

将其更改为immutableBytesWritable，intwritable。

我不确定......希望它有效

hadoop map使用HDFS输入和HBASE输出减少作业

4 个答案:

驱动程序

映射器安培;减速