Question

嗨我发现地图缩减chaining有点问题。我必须形成像这样的链

mapper-＆GT; reducer-＆GT;映射器

从我的第一个mapper到reducer，流程一直很好，这个reducer的输出数据不会正确地映射到下一个map.t这是一个简单的代码示例，我试过了

这是我的第一张映射器

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

    String maxSalary = value.toString().split(",")[4]; 

    outputCollector.collect(new Text("max salary"),new IntWritable(Integer.parseInt(maxSalary)));

}

这是我的减速机

public void reduce(Text key, Iterator<IntWritable> values,
            OutputCollector<Text, IntWritable> outputCollector, Reporter reporter)
            throws IOException {
        int maxSalary = Integer.MIN_VALUE;

        while(values.hasNext()){

            maxSalary = Math.max(maxSalary, values.next().get());
        }
        outputCollector.collect(key, new IntWritable(maxSalary));

    }

这是我的下一个简单的Mapper

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

        System.out.println(value.toString());
    }

这是我运行作业的主要课程

JobConf jobConf = new JobConf(jobrunner.class);
jobConf.setJobName("Chaining");

FileInputFormat.setInputPaths(jobConf, new Path("hdfs://localhost:9000/employee_data.txt"));
FileOutputFormat.setOutputPath(jobConf,new Path("hdfs://localhost:9000/chain9.txt"));

JobConf conf1 = new JobConf(false);

ChainMapper.addMapper(jobConf,chainmap.class,LongWritable.class,Text.class,Text.class,IntWritable.class,true,conf1);

JobConf conf2 = new JobConf(false);

ChainReducer.setReducer(jobConf, chainreduce.class,Text.class,IntWritable.class,Text.class,IntWritable.class,true,conf2);

JobConf conf3 = new JobConf(false);

ChainMapper.addMapper(jobConf, nextchainmap.class, Text.class,IntWritable.class,Text.class,IntWritable.class,true,conf3);


JobClient.runJob(jobConf);

我将在我的减速机中获得最高员工薪水，这必须传递到下一个映射器，在那里它会找到具有最大工资值的员工记录，我怎样才能在下一个映射器中实现这一点？任何想法？

Answer 1

要连接第二张映射器，您需要拨打ChainReducer.addMapper(...)而不是ChainMapper.addMapper(...)。

map减少链接未正确执行

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