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Hadoop Jar runs but no output. Driver, mapper and reduce compiles successfully in namenode

I'm a newbie to Hadoop Programming and I have started learning by setting up Hadoop 2.7.1 on a three node cluster. I have tried running helloworld jars that comes out of the box in Hadoop and it ran fine with success but I wrote my own driver code in my local machine and bundled it into a jar and executed it this way but it fails with NO error messages.
Here is my code and this is what I did.
WordCountMapper.java
package mot.com.bin.test;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
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 WordCountMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable>
{
public void map(LongWritable key, Text Value,
OutputCollector<Text, IntWritable> opc, Reporter r)
throws IOException {
String s = Value.toString();
for (String word :s.split(" ")) {
if( word.length() > 0) {
opc.collect(new Text(word), new IntWritable(1));
}
}
}
}
WordCountReduce.java
package mot.com.bin.test;
import java.io.IOException;
import java.util.Iterator;
import org.apache.hadoop.io.IntWritable;
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 WordCountReduce extends MapReduceBase implements Reducer < Text, IntWritable, Text, IntWritable>{
public void reduce(Text key, Iterator<IntWritable> values,
OutputCollector<Text, IntWritable> opc, Reporter r)
throws IOException {
// TODO Auto-generated method stub
int i = 0;
while (values.hasNext()) {
IntWritable in = values.next();
i+=in.get();
}
opc.collect(key, new IntWritable (i));
}
WordCount.java
/**
* **DRIVER**
*/
package mot.com.bin.test;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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.util.Tool;
import org.apache.hadoop.io.Text;
//import com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider.Text;
/**
* #author rgb764
*
*/
public class WordCount extends Configured implements Tool{
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
}
public int run(String[] arg0) throws Exception {
if (arg0.length < 2) {
System.out.println("Need input file and output directory");
return -1;
}
JobConf conf = new JobConf();
FileInputFormat.setInputPaths(conf, new Path( arg0[0]));
FileOutputFormat.setOutputPath(conf, new Path( arg0[1]));
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(IntWritable.class);
conf.setMapperClass(WordCountMapper.class);
conf.setReducerClass(WordCountReduce.class);
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(IntWritable.class);
JobClient.runJob(conf);
return 0;
}
}
First I tried extracting it as a jar from eclipse and run it in my hadoop cluster. No errors yet no success as well. Then moved my individual java files to my NameNode and compiled each java files and then created the jar file there, still hadoop command returns no results but no errors as well. Kindly help me on this.
hadoop jar WordCout.jar mot.com.bin.test.WordCount /karthik/mytext.txt /tempo
Extracted all dependent jar files using Maven and I added them into the classpath in my name node. Help me figure what and where am I going wrong.

IMO you are missing the code in your main method which instantiate the Tool implementation ( WordCount in your case) and runs the same.
public static void main(String[] args) throws Exception {
int res = ToolRunner.run(new Configuration(), new WordCount(), args);
System.exit(res);
}
Refer this.

Hadoop WordCount code, the following errors are shown

I was reading and implementing this tutorial. At the last, I implement the three classes- Mapper, Reducer and driver. I copied the exact code given on the webpage for all three classes. But following two errors didn't go away:-
Mapper Class
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
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 WordCountMapper extends MapReduceBase // Here WordCountMapper was underlined as error source by Eclipse
implements Mapper<LongWritable, Text, Text, IntWritable> {
private final IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(WritableComparable key, Writable value,
OutputCollector output, Reporter reporter) throws IOException {
String line = value.toString();
StringTokenizer itr = new StringTokenizer(line.toLowerCase());
while(itr.hasMoreTokens()) {
word.set(itr.nextToken());
output.collect(word, one);
}
}
}
The error was:
The type WordCountMapper must implement the inherited abstract method
Mapper.map(LongWritable, Text,
OutputCollector, Reporter)
Driver Class (WordCount.java)
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
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 WordCount {
public static void main(String[] args) {
JobClient client = new JobClient();
JobConf conf = new JobConf(WordCount.class);
// specify output types
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(IntWritable.class);
// specify input and output dirs
FileInputPath.addInputPath(conf, new Path("input")); //////////FileInputPath was underlined
FileOutputPath.addOutputPath(conf, new Path("output")); ////////FileOutputPath as underlined
// specify a mapper
conf.setMapperClass(WordCountMapper.class);
// specify a reducer
conf.setReducerClass(WordCountReducer.class);
conf.setCombinerClass(WordCountReducer.class);
client.setConf(conf);
try {
JobClient.runJob(conf);
} catch (Exception e) {
e.printStackTrace();
}
}
}
The error was:
FileInputPath cannot be resolved
FileOutputPath cannot be resolved

Use this
FileInputFormat.addInputPath(conf, new Path(args[0]));
FileOutputFormat.setOutputPath(conf,new Path(args[1]));
or
FileInputFormat.addInputPath(conf, new Path("inputfile.txt"));
FileOutputFormat.setOutputPath(conf,new Path("outputfile.txt"));
instead of this
// specify input and output dirs
FileInputPath.addInputPath(conf, new Path("input")); //////////FileInputPath was underlined
FileOutputPath.addOutputPath(conf, new Path("output")); ////////FileOutputPath as underlined
This should be the one to import in this case
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;

How to override the default sorting of Hadoop

I have a map-reduce job in which the keys are numbers from 1-200. My intended output was (number,value) in the number order.
But I'm getting the output as :
1 value
10 value
11 value
:
:
2 value
20 value
:
:
3 value
I know this is due to the default behavior of Map-Reduce to sort keys in ascending order.
I want my keys to be sorted in numerical order only. How can I achieve this?

If I had to take a guess, I'd say that you are storing your numbers as Text objects and not IntWritable objects.
Either way, once you have more than one reducer, only the items within a reducer will be sorted, but it won't be totally sorted.

The default WritableComparator in MapReduce framework would normally handle your numerical ordering if the key was IntWritable. I suspect it's getting a Text key thus resulting in lexicographical ordering in your case. Please have a look at the sample code which uses IntWritable key to emit the values:
1) Mapper Implementaion
package com.stackoverflow.answers.mapreduce;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
public class SourceFileMapper extends Mapper<LongWritable, Text, IntWritable, Text> {
private static final String DEFAULT_DELIMITER = "\t";
private IntWritable keyToEmit = new IntWritable();
private Text valueToEmit = new Text();
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String line = value.toString();
keyToEmit.set(Integer.parseInt(line.split(DEFAULT_DELIMITER)[0]));
valueToEmit.set(line.split(DEFAULT_DELIMITER)[1]);
context.write(keyToEmit, valueToEmit);
}
}
2) Reducer Implementation
package com.stackoverflow.answers.mapreduce;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
public class SourceFileReducer extends Reducer<IntWritable, Text, IntWritable, Text> {
public void reduce(IntWritable key, Iterable<Text> values, Context context) throws IOException,
InterruptedException {
for (Text value : values) {
context.write(key, value);
}
}
}
3) Driver Implementation
package com.stackoverflow.answers.mapreduce;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
public class SourceFileDriver {
public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
Path inputPath = new Path(args[0]);
Path outputDir = new Path(args[1]);
// Create configuration
Configuration conf = new Configuration(true);
// Create job
Job job = new Job(conf, "SourceFileDriver");
job.setJarByClass(SourceFileDriver.class);
// Setup MapReduce
job.setMapperClass(SourceFileMapper.class);
job.setReducerClass(SourceFileReducer.class);
job.setNumReduceTasks(1);
// Specify key / value
job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(Text.class);
// Input
FileInputFormat.addInputPath(job, inputPath);
job.setInputFormatClass(TextInputFormat.class);
// Output
FileOutputFormat.setOutputPath(job, outputDir);
job.setOutputFormatClass(TextOutputFormat.class);
// Delete output if exists
FileSystem hdfs = FileSystem.get(conf);
if (hdfs.exists(outputDir))
hdfs.delete(outputDir, true);
// Execute job
int code = job.waitForCompletion(true) ? 0 : 1;
System.exit(code);
}
}
Thank you!

Eclipse - Run on Hadoop does not prompt anything

Im trying to build a simple Wordcount Hadoop project(https://developer.yahoo.com/hadoop/tutorial/module3.html#running) but when I click "Run on Hadoop" there is no action at all...Infact nothing is displayed in the console.
Here is my project structure -
Here is my wordcount job file...
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
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 WordCount {
public static void main(String[] args) {
Configuration config = new Configuration();
config.addResource(new Path("/HADOOP_HOME/conf/hadoop-default.xml"));
config.addResource(new Path("/HADOOP_HOME/conf/hadoop-site.xml"));
JobClient client = new JobClient();
JobConf conf = new JobConf(WordCount.class);
// specify output types
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(IntWritable.class);
// specify input and output dirs
FileInputPath.addInputPath(conf, new Path("input"));
FileOutputPath.addOutputPath(conf, new Path("output"));
// specify a mapper
conf.setMapperClass(WordCountMapper.class);
// specify a reducer
conf.setReducerClass(WordCountReducer.class);
conf.setCombinerClass(WordCountReducer.class);
client.setConf(conf);
try {
JobClient.runJob(conf);
} catch (Exception e) {
e.printStackTrace();
}
}

I think the problem is with the jar file you used for hadoop client to server, So What happens is it tries to stay in the following line and try to search for the server
Configuration config = new Configuration();
Try to debug and let us know if you face any more problem,
If not try the following
Have you tried running the program on eclipse by pointing the core-site , hdfs-site
Configuration.addResource(new Path("path-to-your-core-site.xml file"));
Configuration.addResource(new Path("path-to-your-hdfs-site.xml file"));
and
FileInputPath.addInputPath(hdfs path to your input file);
FileInputPath.addOutputPath(hdfs path to your output file);
See that It works and get back to us

try this,
import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;
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.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
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;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
public class WordCount {
public static class Map extends MapReduceBase implements
Mapper<Object, Text, Text, IntWritable> {
#Override
public void map(Object key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter)
throws IOException {
String line = value.toString();
StringTokenizer tokenizer = new StringTokenizer(line);
System.out.println(line);
while (tokenizer.hasMoreTokens()) {
value.set(tokenizer.nextToken());
output.collect(value, new IntWritable(1));
}
}
}
public static class Reduce extends MapReduceBase implements
Reducer<Text, IntWritable, Text, IntWritable> {
#Override
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,IOException {
JobConf conf = new JobConf(WordCount.class);
conf.setJobName("WordCount");
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(IntWritable.class);
conf.setMapperClass(Map.class);
conf.setReducerClass(Reduce.class);
conf.setInputFormat(TextInputFormat.class);
conf.setOutputFormat(TextOutputFormat.class);
FileInputFormat.setInputPaths(conf, new Path("/home/user17/test.txt"));
FileOutputFormat.setOutputPath(conf, new Path("hdfs://localhost:9000/out2"));
JobClient.runJob(conf);
}
}

I had the exact same problem, and I have just figured it out.
Add parameters in the run configurations.
Right Click WordCount.java > Run As > Run Configurations > Java Application > Word Count > Arguments
Enter this hdfs://hadoop:9000/ hdfs://hadoop:9000/
Apply and Finish Run again.
After running, refresh the project and the result is in the output folder.

Configuration object is null in hadoop mapper

I have the following mapper class. I want to write to hdfs in my mapper function. So I need acces to configuration object which I am retrieving in the setup() method. However it is being returned as null and I am getting a NPE. Can you let me know what am I doing wrong ?
Here is the stacktrace
hduser#nikhil-VirtualBox:/usr/local/hadoop/hadoop-1.0.4$ bin/hadoop jar GWASMapReduce.jar /user/hduser/tet.gpg /user/hduser/output3
12/11/04 08:50:17 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
12/11/04 08:50:24 INFO mapred.FileInputFormat: Total input paths to process : 1
12/11/04 08:50:28 INFO mapred.JobClient: Running job: job_201211031924_0008
12/11/04 08:50:29 INFO mapred.JobClient: map 0% reduce 0%
12/11/04 08:51:35 INFO mapred.JobClient: Task Id : attempt_201211031924_0008_m_000000_0, Status : FAILED
java.lang.NullPointerException
at org.apache.hadoop.fs.FileSystem.getDefaultUri(FileSystem.java:131)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:123)
at com.test.GWASMapper.writeCsvFileSmry(GWASMapper.java:208)
at com.test.GWASMapper.checkForNulls(GWASMapper.java:153)
at com.test.GWASMapper.map(GWASMapper.java:51)
at com.test.GWASMapper.map(GWASMapper.java:1)
at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372)
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)
attempt_201211031924_0008_m_000000_0: ******************************************************************************************************************************************************************************************
attempt_201211031924_0008_m_000000_0: null
attempt_201211031924_0008_m_000000_0: ******************************************************************************************************************************************************************************************
12/11/04 08:51:37 INFO mapred.JobClient: Task Id : attempt_201211031924_0008_m_000001_0, Status : FAILED
Here is my driver class
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
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.util.Tool;
import org.apache.hadoop.util.ToolRunner;
public class GWASMapReduce extends Configured implements Tool{
/**
* #param args
*/
public static void main(String[] args) throws Exception {
Configuration configuration = new Configuration();
ToolRunner.run(configuration, new GWASMapReduce(), args);
}
#Override
public int run(String[] arg0) throws Exception {
JobConf conf = new JobConf();
conf.setInputFormat(GWASInputFormat.class);
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(Text.class);
conf.setJarByClass(GWASMapReduce.class);
conf.setMapperClass(GWASMapper.class);
conf.setNumReduceTasks(0);
FileInputFormat.addInputPath(conf, new Path(arg0[0]));
FileOutputFormat.setOutputPath(conf, new Path(arg0[1]));
JobClient.runJob(conf);
return 0;
}
}
Mapper Class
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileSplit;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import com.google.common.base.Strings;
public class GWASMapper extends MapReduceBase implements Mapper<LongWritable, GWASGenotypeBean, Text, Text> {
private static Configuration conf;
#SuppressWarnings("rawtypes")
public void setup(org.apache.hadoop.mapreduce.Mapper.Context context) throws IOException {
conf = context.getConfiguration();
// conf is null here
}
#Override
public void map(LongWritable inputKey, GWASGenotypeBean inputValue, OutputCollector<Text, Text> output, Reporter reporter) throws IOException {
// mapper code
}
}

I think u r missing this
JobClient jobClient = new JobClient();
client.setConf(conf);
JobClient.runJob(conf);
The conf parameter is not passed to the jobclient. Try this and see if it helps
And I suggest to use the new mapreduce librbary. check the v2.0 for the word count
http://hadoop.apache.org/docs/mapreduce/r0.22.0/mapred_tutorial.html#Example%3A+WordCount+v2.0
And also
try this JobConf job = new JobConf(new Configuration());
I think the configuration object is not initialized here.
And moreover u dont have anything special in the configuration object, so u can initialized the configuration object in the mapper also though which is not a good practice just for trying out

This is just a tip for others facing similar issue:
please make sure that you set the values first and declare a job.
For example:
Configuration conf = new Configuration();
conf.set("a","2");
conf.set("inputpath",args[0]);
//Must be set before the below line:
Job myjob = new Job(conf);
Hope this helps.