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POHadoop : NoSuchMethodException
 

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    <p>This is the job, which joins two relations,</p> <pre><code>import org.apache.hadoop.mapred.*; import org.apache.hadoop.conf.*; import org.apache.hadoop.util.*; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.*; import org.apache.hadoop.contrib.utils.join.*; import java.io.*; public class TwoByTwo extends Configured implements Tool { public static class MapClass extends DataJoinMapperBase { protected Text generateInputTag( String inputFile) { String datasource = inputFile.split( "\\.")[ 0]; return new Text( datasource); }//end generateInputTag protected Text generateGroupKey( TaggedMapOutput aRecord) { String line = ( ( Text) aRecord.getData()).toString(); //between two relations there may be more than one common attributes //so group key has to include all these common attributes. Common //attributes begin with an '_'( underscore). String[] tokens = line.split(","); String groupKey = ""; for( String s : tokens) { if( s.charAt( 0) == '_') { groupKey = groupKey + s; } } return new Text( groupKey); }//end generateGroupKey protected TaggedMapOutput generateTaggedMapOutput( Object value) { TaggedWritable retv = new TaggedWritable( ( Text) value); retv.setTag( this.inputTag); return retv; }//end TaggedMapOutput }//end MapClass public static class Reduce extends DataJoinReducerBase { protected TaggedMapOutput combine( Object[] tags, Object[] values) { if( tags.length &lt; 2) { return null; } String joinedStr = ""; for( int i = 0; i &lt; values.length; i++) { if( i &gt; 0) { joinedStr += ","; } TaggedWritable tw = ( TaggedWritable) values[ i]; String line = ( ( Text) tw.getData()).toString(); String[] tokens = line.split( ",", 2); joinedStr += tokens[ 1]; } TaggedWritable retv = new TaggedWritable( new Text( joinedStr)); retv.setTag( ( Text) tags[ 0]); return retv; }//end TaggedMapOutput }//end Reduce public static class TaggedWritable extends TaggedMapOutput { private Writable data; public TaggedWritable( Writable data) { this.tag = new Text( ""); this.data = data; }//end TaggedWritable public Writable getData() { return data; }//end getData public void write( DataOutput out) throws IOException { this.tag.write( out); this.data.write( out); }//end write public void readFields( DataInput in) throws IOException { this.tag.readFields( in); this.data.readFields( in); }//end readFields }//end TaggedWritable public int run( String[] args) throws Exception { Configuration conf = getConf(); JobConf job = new JobConf( conf, TwoByTwo.class); Path in = new Path( "relations/"); Path out = new Path( "relout/"); FileInputFormat.setInputPaths( job, in); FileOutputFormat.setOutputPath( job, out); job.setJobName( "TwoByTwo"); job.setMapperClass( MapClass.class); job.setReducerClass( Reduce.class); job.setInputFormat( TextInputFormat.class); job.setOutputFormat( TextOutputFormat.class); job.setOutputKeyClass( Text.class); job.setOutputValueClass( TaggedWritable.class); job.set("mapred.textoutputformat.separator", ","); JobClient.runJob( job); return 0; }//end run public static void main( String[] args) throws Exception { int res = ToolRunner.run( new Configuration(), new TwoByTwo(), args); System.exit( res); }//end main } </code></pre> <p>When I run this job,</p> <pre><code>bin/hadoop jar /home/hduser/TwoByTwo.jar TwoByTwo -libjars /usr/local/hadoop/contrib/datajoin/hadoop-datajoin-1.0.3.jar </code></pre> <p>MapClass runs appropriately. When Reduce runs after sometime of running I get this NoSuchMethodException</p> <pre><code>12/10/18 16:38:17 INFO mapred.JobClient: map 100% reduce 27% 12/10/18 16:38:19 INFO mapred.JobClient: Task Id : attempt_201210181416_0013_r_000000_0, Status : FAILED java.lang.RuntimeException: java.lang.NoSuchMethodException: TwoByTwo$TaggedWritable.&lt;init&gt;() at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115) at org.apache.hadoop.io.serializer.WritableSerialization$WritableDeserializer.deserialize(WritableSerialization.java:62) at org.apache.hadoop.io.serializer.WritableSerialization$WritableDeserializer.deserialize(WritableSerialization.java:40) at org.apache.hadoop.mapred.Task$ValuesIterator.readNextValue(Task.java:1271) at org.apache.hadoop.mapred.Task$ValuesIterator.next(Task.java:1211) at org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.moveToNext(ReduceTask.java:249) at org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.next(ReduceTask.java:245) at org.apache.hadoop.contrib.utils.join.DataJoinReducerBase.regroup(DataJoinReducerBase.java:106) at org.apache.hadoop.contrib.utils.join.DataJoinReducerBase.reduce(DataJoinReducerBase.java:129) at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:519) at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:420) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121) at org.apache.hadoop.mapred.Child.main(Child.java:249) Caused by: java.lang.NoSuchMethodException: TwoByTwo$TaggedWritable.&lt;init&gt;() at java.lang.Class.getConstructor0(Class.java:2721) at java.lang.Class.getDeclaredConstructor(Class.java:2002) at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:109) ... 15 more </code></pre> <p>I have problem with nested class TaggedWritable. Why do I have problem with this class on reduce side and not on map side? How can I resolve this error? The constraint of two relations plays any role to the error? Thanks for any help.</p>
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