The version of EmptyInputFormat available in the tarball (I downloaded CDH4 if
that matteres) uses mapred, not mapreduce, and therefore is not compatible with
calls to setInputFormatClass(), so I attempted to extrapolate the pattern of
the old code to an updated version. The class I created can be passed to
setInputFormatClass() without a compile error, and the Hadoop job runs...but
the job uses 0 mappers! The map class isn't called at all, a map slot isn't
even allocated to the job. Clearly, this was not my intent. Any help? Here's
what I put together:
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
/**
* InputFormat which simulates the absence of input data by returning zero
split.
* @param <V>
* @param <K>
*/
public class EmptyInputFormat<V, K> extends InputFormat<K, V> {
@Override
public List<InputSplit> getSplits(JobContext arg0) throws IOException,
InterruptedException {
return new ArrayList<InputSplit>();
}
@Override
public RecordReader<K, V> createRecordReader(InputSplit arg0,
TaskAttemptContext arg1) throws IOException,
InterruptedException {
return new RecordReader<K,V>() {
@Override
public void close() throws IOException { }
@Override
public K getCurrentKey() throws IOException,
InterruptedException {
return null;
}
@Override
public V getCurrentValue() throws IOException,
InterruptedException {
return null;
}
@Override
public float getProgress() throws IOException,
InterruptedException {
return 0;
}
@Override
public void initialize(InputSplit arg0,
TaskAttemptContext arg1)
throws IOException,
InterruptedException {
}
@Override
public boolean nextKeyValue() throws IOException,
InterruptedException {
return false;
}
};
}
}
________________________________________________________________________________
Keith Wiley kwi...@keithwiley.com keithwiley.com music.keithwiley.com
"You can scratch an itch, but you can't itch a scratch. Furthermore, an itch can
itch but a scratch can't scratch. Finally, a scratch can itch, but an itch can't
scratch. All together this implies: He scratched the itch from the scratch that
itched but would never itch the scratch from the itch that scratched."
-- Keith Wiley
________________________________________________________________________________
