Changes between Initial Version and Version 1 of hadoop-sample-code

Timestamp:

May 27, 2008, 4:59:20 PM (18 years ago)

Author:

waue

Comment:

--

hadoop-sample-code

@@ +1 @@
+{{{
+/*
+
+ * hadoop sample code
+ */
+
+
+
+
+import java.io.IOException;
+
+import java.util.Iterator;
+
+import java.util.StringTokenizer;
+
+
+
+import org.apache.hadoop.fs.FileSystem;
+
+import org.apache.hadoop.fs.Path;
+
+import org.apache.hadoop.io.IntWritable;
+
+import org.apache.hadoop.io.LongWritable;
+
+import org.apache.hadoop.io.Text;
+
+import org.apache.hadoop.mapred.JobClient;
+
+import org.apache.hadoop.mapred.JobConf;
+
+import org.apache.hadoop.mapred.MapReduceBase;
+
+import org.apache.hadoop.mapred.Mapper;
+
+import org.apache.hadoop.mapred.OutputCollector;
+
+import org.apache.hadoop.mapred.Reducer;
+
+import org.apache.hadoop.mapred.Reporter;
+
+
+
+
+public class WordCount {
+
+
+
+        // mapper: emits (token, 1) for every word occurrence
+
+        private static class MapClass extends MapReduceBase implements
+
+                        Mapper<LongWritable, Text, Text, IntWritable> {
+
+
+
+                // reuse objects to save overhead of object creation
+
+                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 = ((Text) value).toString();
+
+                        StringTokenizer itr = new StringTokenizer(line);
+
+                        while (itr.hasMoreTokens()) {
+
+                                word.set(itr.nextToken());
+
+                                output.collect(word, one);
+
+                        }
+
+                }
+
+        }
+
+
+
+        // reducer: sums up all the counts
+
+        private static class ReduceClass extends MapReduceBase implements
+
+                        Reducer<Text, IntWritable, Text, IntWritable> {
+
+
+
+                // reuse objects
+
+                private final static IntWritable SumValue = new IntWritable();
+
+
+
+                public void reduce(Text key, Iterator<IntWritable> values,
+
+                                OutputCollector<Text, IntWritable> output, Reporter reporter)
+
+                                throws IOException {
+
+                        // sum up values
+
+                        int sum = 0;
+
+                        while (values.hasNext()) {
+
+                                sum += values.next().get();
+
+                        }
+
+                        SumValue.set(sum);
+
+                        output.collect(key, SumValue);
+
+                }
+
+        }
+
+
+        
+
+        /**
+
+         * Runs the demo.
+
+         */
+
+        public static void main(String[] args) throws IOException {
+
+                String filename = "/user/waue/test/132.txt";
+
+                String outputPath = "sample-counts";
+
+                int mapTasks = 20;
+
+                int reduceTasks = 1;
+
+
+
+                JobConf conf = new JobConf(DemoWordCount.class);
+
+                conf.setJobName("wordcount");
+
+
+
+                conf.setNumMapTasks(mapTasks);
+
+                conf.setNumReduceTasks(reduceTasks);
+
+
+
+                conf.setInputPath(new Path(filename));
+
+                conf.setOutputKeyClass(Text.class);
+
+                conf.setOutputValueClass(IntWritable.class);
+
+                conf.setOutputPath(new Path(outputPath));
+
+
+
+                conf.setMapperClass(MapClass.class);
+
+                conf.setCombinerClass(ReduceClass.class);
+
+                conf.setReducerClass(ReduceClass.class);
+
+                
+
+                // Delete the output directory if it exists already
+
+                Path outputDir = new Path(outputPath);
+
+                FileSystem.get(conf).delete(outputDir);
+
+
+
+                JobClient.runJob(conf);
+
+        }
+
+}
+
+}}}