运行mapreduce作业根本没有输出。它甚至没有运行。很奇怪。终端没有抛出错误

Question

我编译了mapreduce代码（驱动程序，映射器和reducer类）并创建了Jar文件。当我在数据集上运行它时，它似乎无法运行。它只是返回到图像中所示的提示。有人建议吗？

非常感谢 basam

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.lib.input.KeyValueTextInputFormat;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

//This driver program will bring all the information needed to submit this Map reduce job.

public class MultiLangDictionary {

public static void main(String[] args) throws Exception{

    if (args.length !=2){

        System.err.println("Usage: MultiLangDictionary <input path> <output path>");

        System.exit(-1);            

    }



    Configuration conf = new Configuration();



    Job ajob = new Job(conf, "MultiLangDictionary");

     //Assigning the driver class name
    ajob.setJarByClass(MultiLangDictionary.class);


    FileInputFormat.addInputPath(ajob, new Path(args[0]));

    //first argument is the job itself
    //second argument is the location of the output dataset
    FileOutputFormat.setOutputPath(ajob, new Path(args[1]));


    ajob.setInputFormatClass(TextInputFormat.class);



    ajob.setOutputFormatClass(TextOutputFormat.class);


    //Defining the mapper class name
    ajob.setMapperClass(MultiLangDictionaryMapper.class);

    //Defining the Reducer class name
    ajob.setReducerClass(MultiLangDictionaryReducer.class);

    //setting the second argument as a path in a path variable
    Path outputPath = new Path(args[1]);

    //deleting the output path automatically from hdfs so that we don't have delete it explicitly
    outputPath.getFileSystem(conf).delete(outputPath);



}

}

Answer 1

在命令

中尝试使用java packagename.classname

hadoop jar MultiLangDictionary.jar [yourpackagename].MultiLangDictionary input output

Answer 2

您可以尝试将Map和Reduce输出键类型添加到驱动程序中。像（这是一个例子）：

job2.setMapOutputKeyClass(Text.class);
job2.setMapOutputValueClass(Text.class);
job2.setOutputKeyClass(Text.class);
job2.setOutputValueClass(Text.class);

在上面，Mapper和Reducer都会在(Text,Text)方法中编写context.write()。