多个映射器输入和1个reducer输出的Hadoop jar命令错误(连接2个文件中的2个值)

Question

这是我连接两个数据集的示例程序。该程序具有2个映射器和1个归约器，它们将从具有2个不同文件作为输入的2个不同映射器获得的值相加。

我在hadoop-jar命令中得到一个错误。

命令：

hadoop-jar/home/rahul/Downloads/testjars/datajoin.jar datajoin/user/rahul/cust.txt/user/rahul/dedelivery.txt/user/lahul/output

错误：参数数无效Datajoin

实际上，它只期望1个输入路径和1个输出路径，而在我的命令中，我有2个输入用于2个不同的映射器，1个输出。

有人能帮我吗？

代码：

import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.MultipleInputs;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
public class DataJoin {
    public static class TokenizerMapper1 extends Mapper {
        private Text word = new Text();
        public void map(Object key, Text value, Context context)
                throws IOException, InterruptedException {
            String itr[] = value.toString().split("::");
            word.set(itr[0].trim());
            context.write(word, new Text("CD~" + itr[1]));
        }
    }
    public static class TokenizerMapper2 extends Mapper {
        private Text word = new Text();
        public void map(Object key, Text value, Context context)
                throws IOException, InterruptedException {
            String itr[] = value.toString().split("::");
            word.set(itr[0].trim());
            context.write(word, new Text("DD~" + itr[1]));
        }
    }
    public static class IntSumReducer extends Reducer {
        private Text result = new Text();
        public void reduce(Text key, Iterable values, Context context)
                throws IOException, InterruptedException {
            String sum = "";
            for (Text val : values) {
                sum += val.toString();
            }
            result.set(sum);
            context.write(key, result);
        }
    }
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        String[] otherArgs = new GenericOptionsParser(conf, args)
                .getRemainingArgs();
        if (otherArgs.length != 2) {
            System.err.println("Usage: DataJoin ");
            System.exit(2);
        }
        Job job = new Job(conf, "Data Join");
        job.setJarByClass(DataJoin.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        MultipleInputs.addInputPath(job, new Path(otherArgs[0]),
                TextInputFormat.class, TokenizerMapper1.class);
        MultipleInputs.addInputPath(job, new Path(otherArgs[1]),
                TextInputFormat.class, TokenizerMapper2.class);
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[2]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}

Answer 1

您在这部分中有错误

if (otherArgs.length != 2) {
   System.err.println("Usage: DataJoin ");
   System.exit(2);
}

你的论点很有说服力2个输入和1个输出。

参数计数从1,2开始…而不是从0,1开始…

更改为

if (otherArgs.length != 3) {
   System.err.println("Usage: DataJoin ");
   System.exit(0);
}

这解决了您的问题。