Changes between Initial Version and Version 1 of waue/2009/0716

Timestamp:

Jul 16, 2009, 5:38:43 PM (16 years ago)

Author:

waue

Comment:

--

waue/2009/0716

@@ +1 @@
+
+ = 以下在run time時有錯 =
+
+ 原因：Type mismatch in key from map: expected org.apache.hadoop.io.LongWritable, recieved org.apache.hadoop.io.Text 
+
+ Map的key從LongWritable 強制轉型到 String，似乎會遇到一些錯
+
+ * keyvalue.java
+
+{{{
+#!java
+package nchc.keyvalue;
+
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.mapred.FileInputFormat;
+import org.apache.hadoop.mapred.FileOutputFormat;
+import org.apache.hadoop.mapred.JobClient;
+import org.apache.hadoop.mapred.JobConf;
+
+public class keyvalue{
+        public static void main(String[] args) {
+                String[] argv = {"input","oh9","1","1"};
+                args = argv;
+                
+                if (args.length < 4) {
+                        System.out.println("keyvalue <inDir> <outDir> <m> <r>");
+                        return;
+                }
+                
+                JobConf conf = new JobConf(keyvalue.class);
+                conf.setJobName("keyValue");
+                FileInputFormat.setInputPaths(conf, args[0]);
+                FileOutputFormat.setOutputPath(conf, new Path(args[1]));
+                conf.setNumMapTasks(Integer.parseInt(args[2]));
+                conf.setNumReduceTasks(Integer.parseInt(args[3]));
+                conf.setMapperClass(kvM.class);
+                conf.setReducerClass(kvR.class);
+
+                long start = System.nanoTime();
+                try {
+                        JobClient.runJob(conf);
+                } catch (Exception e) {
+                        e.printStackTrace();
+                }
+                long period = System.nanoTime() - start;
+                System.err.println(period*(1e-9) + " secs.");
+        }
+}
+
+}}}
+
+ * kvm.java
+
+{{{
+package nchc.keyvalue;
+
+import java.io.IOException;
+
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.mapred.MapReduceBase;
+import org.apache.hadoop.mapred.Mapper;
+import org.apache.hadoop.mapred.OutputCollector;
+import org.apache.hadoop.mapred.Reporter;
+
+public class kvM extends MapReduceBase implements
+                Mapper<LongWritable, Text, Text, Text> {
+
+        public void map(LongWritable key, Text value,
+                        OutputCollector<Text, Text> output, Reporter report)
+                        throws IOException {
+                Text keyv = new Text(key.toString());
+                output.collect(keyv, value);
+        }
+
+}
+}}}
+
+ * kvr.java
+
+{{{
+package nchc.keyvalue;
+
+import java.io.IOException;
+import java.util.Iterator;
+
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.mapred.MapReduceBase;
+import org.apache.hadoop.mapred.OutputCollector;
+import org.apache.hadoop.mapred.Reducer;
+import org.apache.hadoop.mapred.Reporter;
+
+public class kvR extends MapReduceBase implements
+                Reducer< Text, Text, Text, Text> {
+        public void reduce(Text key, Iterator<Text> values,
+                        OutputCollector<Text, Text> output, Reporter report)
+                        throws IOException {
+                while (values.hasNext()) {
+                        Text keyv = new Text("< "+key+" , ");
+                        Text val = new Text(values.next()+">");
+                        output.collect(keyv, val);
+                }
+        }
+}
+}}}