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Hadoop ChainMapper，ChainReducer

转载 作者：可可西里 更新时间：2023-11-01 14:18:50 24 4
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<分区>

我是 Hadoop 的新手，正在尝试弄清楚如何使用 ChainMapper、ChainReducer 以编程方式链接作业(多个映射器、reducer)。我找到了一些部分示例，但没有找到一个完整且有效的示例。

我目前的测试代码是

public class ChainJobs extends Configured implements Tool {

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

    private final static 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();
        StringTokenizer tokenizer = new StringTokenizer(line);
        while (tokenizer.hasMoreTokens()) {
            word.set(tokenizer.nextToken());
            output.collect(word, one);
        }
    }
}

public static class Map2 extends MapReduceBase implements Mapper<Text, IntWritable, Text, IntWritable> {

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

    @Override
    public void map(Text key, IntWritable value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
        String line = value.toString();
        StringTokenizer tokenizer = new StringTokenizer(line);
        while (tokenizer.hasMoreTokens()) {
            word.set(tokenizer.nextToken().concat("Justatest"));
            output.collect(word, one);
        }
    }
}

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

    @Override
    public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
        int sum = 0;
        while (values.hasNext()) {
            sum += values.next().get();
        }
        output.collect(key, new IntWritable(sum));
    }
}

@Override
public int run(String[] args)  {

    Configuration conf = getConf();
    JobConf job = new JobConf(conf);

    job.setJobName("TestforChainJobs");
    FileInputFormat.setInputPaths(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    JobConf map1Conf = new JobConf(false);
    ChainMapper.addMapper(job, Map.class, LongWritable.class, Text.class, Text.class, IntWritable.class, true, map1Conf);

    JobConf map2Conf = new JobConf(false);
    ChainMapper.addMapper(job, Map2.class, Text.class, IntWritable.class, Text.class, IntWritable.class, true, map2Conf);

    JobConf reduceConf = new JobConf(false);
    ChainReducer.setReducer(job, Reduce.class, Text.class, IntWritable.class, Text.class, IntWritable.class, true, reduceConf);

    JobClient.runJob(job);
    return 0;

     }

}

public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(new Configuration(), new ChainJobs(), args);
    System.exit(res);
}

但是失败了

MapAttempt TASK_TYPE="MAP" TASKID="task_201210162337_0009_m_000000" TASK_ATTEMPT_ID="attempt_201210162337_0009_m_000000_0" TASK_STATUS="FAILED" FINISH_TIME="1350397216365" HOSTNAME="localhost\.localdomain" ERROR="java\.lang\.RuntimeException: Error in configuring object
    at org\.apache\.hadoop\.util\.ReflectionUtils\.setJobConf(ReflectionUtils\.java:106)
    at org\.apache\.hadoop\.util\.ReflectionUtils\.setConf(ReflectionUtils\.java:72)
    at org\.apache\.hadoop\.util\.ReflectionUtils\.newInstance(ReflectionUtils\.java:130)
    at org\.apache\.hadoop\.mapred\.MapTask\.runOldMapper(MapTask\.java:389)
    at org\.apache\.hadoop\.mapred\.MapTask\.run(MapTask\.java:327)
    at org\.apache\.hadoop\.mapred\.Child$4\.run(Child\.java:268)
    at java\.security\.AccessController\.doPrivileged(Native Method)
    at javax\.security\.auth\.Subject\.doAs(Subject\.java:396)

非常感谢任何提示或非常简单的工作示例。

24 4 0
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