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Posted to common-dev@hadoop.apache.org by LopezGG <lo...@gmail.com> on 2012/04/18 04:49:51 UTC
Reduce side join - Hadoop default - error in combiner
I am using the folllowing code to do the reduce side join
/*
* HadoopMapper.java
*
* Created on Apr 8, 2012, 5:39:51 PM
*/
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
// import org.apache.commons.logging.Log;
// import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.contrib.utils.join.*;
/**
*
* @author
*/
public class DataJoin extends Configured implements Tool
{
public static class MapClass extends DataJoinMapperBase
{
protected Text generateInputTag(String inputFile)
{
String datasource = inputFile.split("-")[0];
return new Text(datasource);
}
protected Text generateGroupKey(TaggedMapOutput aRecord)
{
String line = ((Text) aRecord.getData()).toString();
String[] tokens = line.split(",");
String groupKey = tokens[0];
return new Text(groupKey);
}
protected TaggedMapOutput generateTaggedMapOutput(Object
value)
{
TaggedWritable retv = new TaggedWritable((Text)
value);
retv.setTag(this.inputTag);
return retv;
}
}
public static class Reduce extends DataJoinReducerBase
{
protected TaggedMapOutput combine(Object[] tags,
Object[] values)
{
if (tags.length < 2) return null;
String joinedStr = "";
for (int i=0; i<values.length; i++)
{
if (i > 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;
}
}
public static class TaggedWritable extends TaggedMapOutput
{
private Writable data;
public TaggedWritable(Writable data)
{
this.tag = new Text("");
this.data = data;
}
public Writable getData()
{
return data;
}
public void write(DataOutput out) throws IOException
{
this.tag.write(out);
this.data.write(out);
}
public void readFields(DataInput in) throws IOException
{
this.tag.readFields(in);
this.data.readFields(in);
}
}
public int run(String[] args) throws Exception
{
Configuration conf = getConf();
JobConf job = new JobConf(conf, DataJoin.class);
String[] otherArgs = new
GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length != 2)
{
System.err.println("Usage: wordcount
<in> <out>");
System.exit(2);
}
Path in = new Path(args[0]);
Path out = new Path(args[1]);
FileInputFormat.setInputPaths(job, in);
FileOutputFormat.setOutputPath(job, out);
job.setJobName("DataJoin");
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;
}
public static void main(String[] args) throws Exception
{
int res = ToolRunner.run(new Configuration(),
new DataJoin(),
args);
System.exit(res);
}
}
I am able to compile my code. When I run in hadoop I am getting the
following error with the combiner
12/04/17 19:59:29 INFO mapred.JobClient: map 100% reduce 27%
12/04/17 19:59:38 INFO mapred.JobClient: map 100% reduce 30%
12/04/17 19:59:47 INFO mapred.JobClient: map 100% reduce 33%
12/04/17 20:00:23 INFO mapred.JobClient: Task Id :
attempt_201204061316_0018_r_000000_2, Status : FAILED
java.lang.RuntimeException: java.lang.NoSuchMethodException:
DataJoin$TaggedWritable.<init>()
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
at
org.apache.hadoop.io.serializer.WritableSerialization$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:1136)
at
org.apache.hadoop.mapred.Task$ValuesIterator.next(Task.java:1076)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.moveToNext(ReduceTask.java:246)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.next(ReduceTask.java:242)
at
org.apache.hadoop.contrib.utils.join.DataJoinReducerBase.regroup(DataJoinReducerBase.java:106)
I checked some forums and found out that the error may occur due to non
static class. My program has no non static class!
The command I use to run hadoop is
/hadoop/core/bin/hadoop jar /export/scratch/lopez/Join/DataJoin.jar
DataJoin /export/scratch/user/lopez/Join
/export/scratch/user/lopez/Join_Output
and the DataJoin.jar file has DataJoin$TaggedWritable packaged in it
Could someone please help me
--
View this message in context: http://old.nabble.com/Reduce-side-join---Hadoop-default---error-in-combiner-tp33705493p33705493.html
Sent from the Hadoop core-dev mailing list archive at Nabble.com.
Re: Reduce side join - Hadoop default - error in combiner
Posted by Harsh J <ha...@cloudera.com>.
I filed https://issues.apache.org/jira/browse/HADOOP-8297 for documenting this.
On Wed, Apr 18, 2012 at 9:02 AM, Devaraj k <de...@huawei.com> wrote:
> Hi Lopez,
>
> You need to have default constructor for TaggedWritable because while deserializing it creates instance using default constructor and calls the readFields() on it.
>
>
> Thanks
> Devaraj
>
> ________________________________________
> From: LopezGG [lopezgilsinia@gmail.com]
> Sent: Wednesday, April 18, 2012 8:19 AM
> To: core-dev@hadoop.apache.org
> Subject: Reduce side join - Hadoop default - error in combiner
>
> I am using the folllowing code to do the reduce side join
>
>
>
>
> /*
> * HadoopMapper.java
> *
> * Created on Apr 8, 2012, 5:39:51 PM
> */
>
>
> import java.io.DataInput;
> import java.io.DataOutput;
> import java.io.IOException;
> // import org.apache.commons.logging.Log;
> // import org.apache.commons.logging.LogFactory;
> import org.apache.hadoop.mapred.FileInputFormat;
> import org.apache.hadoop.mapred.FileOutputFormat;
> import org.apache.hadoop.mapred.JobClient;
> import org.apache.hadoop.mapred.JobConf;
> import org.apache.hadoop.mapred.TextInputFormat;
> import org.apache.hadoop.mapred.TextOutputFormat;
> import org.apache.hadoop.util.GenericOptionsParser;
> import org.apache.hadoop.util.Tool;
> import org.apache.hadoop.util.ToolRunner;
> import org.apache.hadoop.fs.Path;
> import org.apache.hadoop.io.Text;
> import org.apache.hadoop.io.Writable;
> import org.apache.hadoop.conf.Configuration;
> import org.apache.hadoop.conf.Configured;
> import org.apache.hadoop.contrib.utils.join.*;
>
> /**
> *
> * @author
> */
> public class DataJoin extends Configured implements Tool
> {
> public static class MapClass extends DataJoinMapperBase
> {
> protected Text generateInputTag(String inputFile)
> {
> String datasource = inputFile.split("-")[0];
> return new Text(datasource);
> }
> protected Text generateGroupKey(TaggedMapOutput aRecord)
> {
> String line = ((Text) aRecord.getData()).toString();
> String[] tokens = line.split(",");
> String groupKey = tokens[0];
> return new Text(groupKey);
> }
> protected TaggedMapOutput generateTaggedMapOutput(Object
> value)
> {
> TaggedWritable retv = new TaggedWritable((Text)
> value);
> retv.setTag(this.inputTag);
> return retv;
> }
> }
> public static class Reduce extends DataJoinReducerBase
> {
> protected TaggedMapOutput combine(Object[] tags,
> Object[] values)
> {
> if (tags.length < 2) return null;
> String joinedStr = "";
> for (int i=0; i<values.length; i++)
> {
> if (i > 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;
> }
> }
> public static class TaggedWritable extends TaggedMapOutput
> {
> private Writable data;
> public TaggedWritable(Writable data)
> {
> this.tag = new Text("");
> this.data = data;
> }
>
> public Writable getData()
> {
> return data;
> }
> public void write(DataOutput out) throws IOException
> {
> this.tag.write(out);
> this.data.write(out);
> }
> public void readFields(DataInput in) throws IOException
> {
> this.tag.readFields(in);
> this.data.readFields(in);
> }
> }
> public int run(String[] args) throws Exception
> {
>
>
> Configuration conf = getConf();
> JobConf job = new JobConf(conf, DataJoin.class);
> String[] otherArgs = new
> GenericOptionsParser(conf, args).getRemainingArgs();
> if (otherArgs.length != 2)
> {
> System.err.println("Usage: wordcount
> <in> <out>");
> System.exit(2);
> }
>
> Path in = new Path(args[0]);
> Path out = new Path(args[1]);
> FileInputFormat.setInputPaths(job, in);
> FileOutputFormat.setOutputPath(job, out);
> job.setJobName("DataJoin");
> 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;
> }
> public static void main(String[] args) throws Exception
> {
> int res = ToolRunner.run(new Configuration(),
> new DataJoin(),
> args);
> System.exit(res);
> }
> }
>
>
>
>
> I am able to compile my code. When I run in hadoop I am getting the
> following error with the combiner
>
>
> 12/04/17 19:59:29 INFO mapred.JobClient: map 100% reduce 27%
> 12/04/17 19:59:38 INFO mapred.JobClient: map 100% reduce 30%
> 12/04/17 19:59:47 INFO mapred.JobClient: map 100% reduce 33%
> 12/04/17 20:00:23 INFO mapred.JobClient: Task Id :
> attempt_201204061316_0018_r_000000_2, Status : FAILED
> java.lang.RuntimeException: java.lang.NoSuchMethodException:
> DataJoin$TaggedWritable.<init>()
> at
> org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
> at
> org.apache.hadoop.io.serializer.WritableSerialization$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:1136)
> at
> org.apache.hadoop.mapred.Task$ValuesIterator.next(Task.java:1076)
> at
> org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.moveToNext(ReduceTask.java:246)
> at
> org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.next(ReduceTask.java:242)
> at
> org.apache.hadoop.contrib.utils.join.DataJoinReducerBase.regroup(DataJoinReducerBase.java:106)
>
>
> I checked some forums and found out that the error may occur due to non
> static class. My program has no non static class!
>
> The command I use to run hadoop is
> /hadoop/core/bin/hadoop jar /export/scratch/lopez/Join/DataJoin.jar
> DataJoin /export/scratch/user/lopez/Join
> /export/scratch/user/lopez/Join_Output
>
> and the DataJoin.jar file has DataJoin$TaggedWritable packaged in it
>
> Could someone please help me
> --
> View this message in context: http://old.nabble.com/Reduce-side-join---Hadoop-default---error-in-combiner-tp33705493p33705493.html
> Sent from the Hadoop core-dev mailing list archive at Nabble.com.
--
Harsh J
RE: Reduce side join - Hadoop default - error in combiner
Posted by Devaraj k <de...@huawei.com>.
Hi Lopez,
You need to have default constructor for TaggedWritable because while deserializing it creates instance using default constructor and calls the readFields() on it.
Thanks
Devaraj
________________________________________
From: LopezGG [lopezgilsinia@gmail.com]
Sent: Wednesday, April 18, 2012 8:19 AM
To: core-dev@hadoop.apache.org
Subject: Reduce side join - Hadoop default - error in combiner
I am using the folllowing code to do the reduce side join
/*
* HadoopMapper.java
*
* Created on Apr 8, 2012, 5:39:51 PM
*/
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
// import org.apache.commons.logging.Log;
// import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.contrib.utils.join.*;
/**
*
* @author
*/
public class DataJoin extends Configured implements Tool
{
public static class MapClass extends DataJoinMapperBase
{
protected Text generateInputTag(String inputFile)
{
String datasource = inputFile.split("-")[0];
return new Text(datasource);
}
protected Text generateGroupKey(TaggedMapOutput aRecord)
{
String line = ((Text) aRecord.getData()).toString();
String[] tokens = line.split(",");
String groupKey = tokens[0];
return new Text(groupKey);
}
protected TaggedMapOutput generateTaggedMapOutput(Object
value)
{
TaggedWritable retv = new TaggedWritable((Text)
value);
retv.setTag(this.inputTag);
return retv;
}
}
public static class Reduce extends DataJoinReducerBase
{
protected TaggedMapOutput combine(Object[] tags,
Object[] values)
{
if (tags.length < 2) return null;
String joinedStr = "";
for (int i=0; i<values.length; i++)
{
if (i > 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;
}
}
public static class TaggedWritable extends TaggedMapOutput
{
private Writable data;
public TaggedWritable(Writable data)
{
this.tag = new Text("");
this.data = data;
}
public Writable getData()
{
return data;
}
public void write(DataOutput out) throws IOException
{
this.tag.write(out);
this.data.write(out);
}
public void readFields(DataInput in) throws IOException
{
this.tag.readFields(in);
this.data.readFields(in);
}
}
public int run(String[] args) throws Exception
{
Configuration conf = getConf();
JobConf job = new JobConf(conf, DataJoin.class);
String[] otherArgs = new
GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length != 2)
{
System.err.println("Usage: wordcount
<in> <out>");
System.exit(2);
}
Path in = new Path(args[0]);
Path out = new Path(args[1]);
FileInputFormat.setInputPaths(job, in);
FileOutputFormat.setOutputPath(job, out);
job.setJobName("DataJoin");
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;
}
public static void main(String[] args) throws Exception
{
int res = ToolRunner.run(new Configuration(),
new DataJoin(),
args);
System.exit(res);
}
}
I am able to compile my code. When I run in hadoop I am getting the
following error with the combiner
12/04/17 19:59:29 INFO mapred.JobClient: map 100% reduce 27%
12/04/17 19:59:38 INFO mapred.JobClient: map 100% reduce 30%
12/04/17 19:59:47 INFO mapred.JobClient: map 100% reduce 33%
12/04/17 20:00:23 INFO mapred.JobClient: Task Id :
attempt_201204061316_0018_r_000000_2, Status : FAILED
java.lang.RuntimeException: java.lang.NoSuchMethodException:
DataJoin$TaggedWritable.<init>()
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
at
org.apache.hadoop.io.serializer.WritableSerialization$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:1136)
at
org.apache.hadoop.mapred.Task$ValuesIterator.next(Task.java:1076)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.moveToNext(ReduceTask.java:246)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.next(ReduceTask.java:242)
at
org.apache.hadoop.contrib.utils.join.DataJoinReducerBase.regroup(DataJoinReducerBase.java:106)
I checked some forums and found out that the error may occur due to non
static class. My program has no non static class!
The command I use to run hadoop is
/hadoop/core/bin/hadoop jar /export/scratch/lopez/Join/DataJoin.jar
DataJoin /export/scratch/user/lopez/Join
/export/scratch/user/lopez/Join_Output
and the DataJoin.jar file has DataJoin$TaggedWritable packaged in it
Could someone please help me
--
View this message in context: http://old.nabble.com/Reduce-side-join---Hadoop-default---error-in-combiner-tp33705493p33705493.html
Sent from the Hadoop core-dev mailing list archive at Nabble.com.
Re: Reduce side join - Hadoop default - error in combiner
Posted by yuliya Feldman <yu...@yahoo.com>.
It looks for default constructor which you don't have in class TaggedWritable
________________________________
From: LopezGG <lo...@gmail.com>
To: core-dev@hadoop.apache.org
Sent: Tuesday, April 17, 2012 7:49 PM
Subject: Reduce side join - Hadoop default - error in combiner
I am using the folllowing code to do the reduce side join
/*
* HadoopMapper.java
*
* Created on Apr 8, 2012, 5:39:51 PM
*/
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
// import org.apache.commons.logging.Log;
// import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.contrib.utils.join.*;
/**
*
* @author
*/
public class DataJoin extends Configured implements Tool
{
public static class MapClass extends DataJoinMapperBase
{
protected Text generateInputTag(String inputFile)
{
String datasource = inputFile.split("-")[0];
return new Text(datasource);
}
protected Text generateGroupKey(TaggedMapOutput aRecord)
{
String line = ((Text) aRecord.getData()).toString();
String[] tokens = line.split(",");
String groupKey = tokens[0];
return new Text(groupKey);
}
protected TaggedMapOutput generateTaggedMapOutput(Object
value)
{
TaggedWritable retv = new TaggedWritable((Text)
value);
retv.setTag(this.inputTag);
return retv;
}
}
public static class Reduce extends DataJoinReducerBase
{
protected TaggedMapOutput combine(Object[] tags,
Object[] values)
{
if (tags.length < 2) return null;
String joinedStr = "";
for (int i=0; i<values.length; i++)
{
if (i > 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;
}
}
public static class TaggedWritable extends TaggedMapOutput
{
private Writable data;
public TaggedWritable(Writable data)
{
this.tag = new Text("");
this.data = data;
}
public Writable getData()
{
return data;
}
public void write(DataOutput out) throws IOException
{
this.tag.write(out);
this.data.write(out);
}
public void readFields(DataInput in) throws IOException
{
this.tag.readFields(in);
this.data.readFields(in);
}
}
public int run(String[] args) throws Exception
{
Configuration conf = getConf();
JobConf job = new JobConf(conf, DataJoin.class);
String[] otherArgs = new
GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length != 2)
{
System.err.println("Usage: wordcount
<in> <out>");
System.exit(2);
}
Path in = new Path(args[0]);
Path out = new Path(args[1]);
FileInputFormat.setInputPaths(job, in);
FileOutputFormat.setOutputPath(job, out);
job.setJobName("DataJoin");
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;
}
public static void main(String[] args) throws Exception
{
int res = ToolRunner.run(new Configuration(),
new DataJoin(),
args);
System.exit(res);
}
}
I am able to compile my code. When I run in hadoop I am getting the
following error with the combiner
12/04/17 19:59:29 INFO mapred.JobClient: map 100% reduce 27%
12/04/17 19:59:38 INFO mapred.JobClient: map 100% reduce 30%
12/04/17 19:59:47 INFO mapred.JobClient: map 100% reduce 33%
12/04/17 20:00:23 INFO mapred.JobClient: Task Id :
attempt_201204061316_0018_r_000000_2, Status : FAILED
java.lang.RuntimeException: java.lang.NoSuchMethodException:
DataJoin$TaggedWritable.<init>()
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
at
org.apache.hadoop.io.serializer.WritableSerialization$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:1136)
at
org.apache.hadoop.mapred.Task$ValuesIterator.next(Task.java:1076)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.moveToNext(ReduceTask.java:246)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.next(ReduceTask.java:242)
at
org.apache.hadoop.contrib.utils.join.DataJoinReducerBase.regroup(DataJoinReducerBase.java:106)
I checked some forums and found out that the error may occur due to non
static class. My program has no non static class!
The command I use to run hadoop is
/hadoop/core/bin/hadoop jar /export/scratch/lopez/Join/DataJoin.jar
DataJoin /export/scratch/user/lopez/Join
/export/scratch/user/lopez/Join_Output
and the DataJoin.jar file has DataJoin$TaggedWritable packaged in it
Could someone please help me
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