Hadoop Not Finding Map Class - hadoop

Question

I am using hadoop-1.2.1 and trying to run a simple RowCount HBase job using ToolRunner. However, no matter what I seem to try, hadoop cannot find the map class. The jar file is being copied correctly into hdfs, but I can't seem to figure out where it is going wrong. Please help!
Here is the code:
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.output.NullOutputFormat;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
public class HBaseRowCountToolRunnerTest extends Configured implements Tool
{
// What to copy.
public static final String JAR_NAME = "myJar.jar";
public static final String LOCAL_JAR = <path_to_jar> + JAR_NAME;
public static final String REMOTE_JAR = "/tmp/"+JAR_NAME;
public static void main(String[] args) throws Exception
{
Configuration config = HBaseConfiguration.create();
//All connection configs set here -- omitted to post the code
config.set("tmpjars", REMOTE_JAR);
FileSystem dfs = FileSystem.get(config);
System.out.println("pathString = " + (new Path(LOCAL_JAR)).toString() + " \n");
// Copy jar file to remote.
dfs.copyFromLocalFile(new Path(LOCAL_JAR), new Path(REMOTE_JAR));
// Get rid of jar file when we're done.
dfs.deleteOnExit(new Path(REMOTE_JAR));
// Run the job.
System.exit(ToolRunner.run(config, new HBaseRowCountToolRunnerTest(), args));
}
#Override
public int run(String[] args) throws Exception
{
Job job = new RowCountJob(getConf(), "testJob", "myLittleHBaseTable");
return job.waitForCompletion(true) ? 0 : 1;
}
public static class RowCountJob extends Job
{
RowCountJob(Configuration conf, String jobName, String tableName) throws IOException
{
super(conf, RowCountJob.class.getCanonicalName() + "_" + jobName);
setJarByClass(getClass());
Scan scan = new Scan();
scan.setCacheBlocks(false);
scan.setFilter(new FirstKeyOnlyFilter());
setOutputFormatClass(NullOutputFormat.class);
TableMapReduceUtil.initTableMapperJob(tableName, scan,
RowCounterMapper.class, ImmutableBytesWritable.class, Result.class, this);
setNumReduceTasks(0);
}
}//end public static class RowCountJob extends Job
//Mapper that runs the count
//TableMapper -- TableMapper<KEYOUT, VALUEOUT> (*OUT by type)
public static class RowCounterMapper extends TableMapper<ImmutableBytesWritable, Result>
{
//Counter enumeration to count the actual rows
public static enum Counters {ROWS}
/**
* Maps the data.
*
* #param row The current table row key.
* #param values The columns.
* #param context The current context.
* #throws IOException When something is broken with the data.
* #see org.apache.hadoop.mapreduce.Mapper#map(KEYIN, VALUEIN,
* org.apache.hadoop.mapreduce.Mapper.Context)
*/
#Override
public void map(ImmutableBytesWritable row, Result values, Context context) throws IOException
{
// Count every row containing data times 2, whether it's in qualifiers or values
context.getCounter(Counters.ROWS).increment(2);
}
}//end public static class RowCounterMapper extends TableMapper<ImmutableBytesWritable, Result>
}//end public static void main(String[] args) throws Exception

Answer 1

Ok- I found a workaround to the problem and thought that I would share for all others having similar issues...
As is turns out, I abandoned the tmpjars configuration option and just copied the jar file directed into the DistributedCache from the code itself. Here is what it looks like:
// Copy jar file to remote.
FileSystem dfs = FileSystem.get(conf);
dfs.copyFromLocalFile(new Path(LOCAL_JAR), new Path(REMOTE_JAR));
// Get rid of jar file when we're done.
dfs.deleteOnExit(new Path(REMOTE_JAR));
//Place it in the distributed cache
DistributedCache.addFileToClassPath(new Path(REMOTE_JAR), conf, dfs);
Perhaps it doesn't solve what is going on with tmpjars, but it does work.

Answer 2

I got the same problem today.Finally, I found it was because I forgot to insert the following sentence in the driver class...
job.setJarByClass(HBaseTestDriver.class);