Hadoop映射器和reducer值类型不匹配错误

Question

public class WordCountMapper extends MapReduceBase
    implements Mapper<LongWritable, Text, Text, IntWritable> {

  private final IntWritable one = new IntWritable(1);
  private Text word = new Text();

  public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable>
        output, Reporter reporter) throws IOException {

    String line = value.toString();
    String[] words = line.split(",");
    String[] date = words[2].split(" ");
      word.set(date[0]+" "+date[1]+" "+date[2]);
      if(words[0].contains("0"))
          one.set(0);
      else
          one.set(4);
      output.collect(word, one);

  }
}

-----------------------------------------------------------------------------------

public class WordCountReducer extends MapReduceBase
    implements Reducer<Text, IntWritable, Text, Text> {

  public void reduce(Text key,Iterator<IntWritable> values,
                  OutputCollector<Text, Text> output,
                  Reporter reporter) throws IOException {

    int sad = 0;
    int happy = 0;
    while (values.hasNext()) {
      IntWritable value = (IntWritable) values.next();
      if(value.get() == 0)
          sad++; // process value
      else
          happy++;
    }

    output.collect(key, new Text("sad:"+sad+", happy:"+happy));
  }
}
---------------------------------------------------------------------------------

public class WordCount {

  public static void main(String[] args) {
    JobClient client = new JobClient();
    JobConf conf = new JobConf(WordCount.class);

    // specify output types
    conf.setOutputKeyClass(Text.class);
    conf.setOutputValueClass(IntWritable.class);

    // specify input and output dirs
    FileInputFormat.addInputPath(conf, new Path("input"));
    FileOutputFormat.setOutputPath(conf, new Path("output"));

    // specify a mapper
    conf.setMapperClass(WordCountMapper.class);

    // specify a reducer
    conf.setReducerClass(WordCountReducer.class);
    conf.setCombinerClass(WordCountReducer.class);

    client.setConf(conf);
    try {
      JobClient.runJob(conf);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

我得到这个错误：

14/12/10 18:11:01 INFO Mapred.JobClient：任务Id:Attest_201412100143_0008_M_000000_0,状态：失败java.io.ioException：溢出在org.apache.hadoop.mapred.maptask$MapOutputBuffer.Collect(maptask.java:425)在wordcountmapper.map（wordcountmapper.java:31)在wordcountmapper.map（wordcountmapper.java:1)在org.apache.hadoop.mapred.maprunner.run在org.apache.hadoop.mapred.maptask处询问$MapOutputBuffer.sortandSpill（MapTask.java:785)$MapOutputBuffer.Access$1600（MapTask.java:286)，在org.apache.hadoop.mapred.maptask$MapOutputBuffer.sortandSpill（MapTask.java:712)处询问$MapOutputBuffer.sortandSpill（MapTask.java

在此之后，错误会重复发生几次。有人能解释一下为什么会出现这个错误吗？我搜索了与此类似的错误，但我发现的所有错误都是映射器和还原器的键值类型不匹配，但正如我所看到的，映射器和还原器的键值类型匹配。提前谢谢你。

Answer 1

尝试评论

conf.SetCombinerClass（WordCountReducer.Class）；

然后跑。

job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);

job.setOutputKeyClass(Text.class);
job.setOutputValueClass(Text.class);

如果两者都发出相同的数据类型，则

job.setOutputKeyClass();
job.setOutputValueClass();