Unable to set partitoner to the JobConf object

问题

I wrote a custom partitioner but am unable to set it to the JobConf object in the main class.

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Partitioner;

public class FirstCharTextPartitioner extends Partitioner<Text, Text> {

    @Override
    public int getPartition(Text key, Text value, int numReduceTasks) {
        return (key.toString().charAt(0)) % numReduceTasks;
    }    
}

But when I try to set this to the JobConf object, I get the following error.
The method setPartitionerClass(Class) in the type JobConf is not applicable for the arguments (Class)

public class WordCount {

    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();
            String[] tokens = line.split("\\s");
            for (String token : tokens) {
                word.set(token);
                output.collect(word, one);
            }
        }
    }

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

    public static void main(String[] args) throws Exception {
        JobConf conf = new JobConf(WordCount.class);
        conf.setJobName("wordcount");

        conf.setOutputKeyClass(Text.class);
        conf.setOutputValueClass(IntWritable.class);

        conf.setMapperClass(Map.class);
        conf.setCombinerClass(Reduce.class);
        conf.setReducerClass(Reduce.class);
        conf.setPartitionerClass(FirstCharTextPartitioner.class);

        conf.setInputFormat(TextInputFormat.class);
        conf.setOutputFormat(TextOutputFormat.class);

        FileInputFormat.setInputPaths(conf, new Path(args[0]));
        FileOutputFormat.setOutputPath(conf, new Path(args[1]));

        JobClient.runJob(conf);
    }
}

Can someone please tell me what I am doing wrong?

回答1:

You are importing the new org.apache.hadoop.mapreduce.Partitioner.

You need to implement the old interface org.apache.hadoop.mapred.Partitioner, like this:

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.Partitioner;

public class FirstCharTextPartitioner implements Partitioner<Text, Text> {

    @Override
    public int getPartition(Text key, Text value, int numReduceTasks) {
        return (key.toString().charAt(0)) % numReduceTasks;
    }    
}

来源：https://stackoverflow.com/questions/14193646/unable-to-set-partitoner-to-the-jobconf-object

标签

Hadoop

MapReduce

hadoop-partitioning