Package org.apache.hadoop.hbase.mapreduce

Class NMapInputFormat

java.lang.Object

org.apache.hadoop.mapreduce.InputFormat<org.apache.hadoop.io.NullWritable,org.apache.hadoop.io.NullWritable>

org.apache.hadoop.hbase.mapreduce.NMapInputFormat

public class NMapInputFormat
extends org.apache.hadoop.mapreduce.InputFormat<org.apache.hadoop.io.NullWritable,org.apache.hadoop.io.NullWritable>

Input format that creates a configurable number of map tasks each provided with a single row of NullWritables. This can be useful when trying to write mappers which don't have any real input (eg when the mapper is simply producing random data as output)

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	NMapInputFormat.NullInputSplit
private static class	NMapInputFormat.SingleRecordReader<K,V>

Field Summary

Fields

Modifier and Type	Field	Description
private static final String	NMAPS_KEY

Constructor Summary

Constructors

Constructor	Description
NMapInputFormat()

Method Summary

Modifier and Type	Method	Description
org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.NullWritable,org.apache.hadoop.io.NullWritable>	createRecordReader(org.apache.hadoop.mapreduce.InputSplit split, org.apache.hadoop.mapreduce.TaskAttemptContext tac)
static int	getNumMapTasks(org.apache.hadoop.conf.Configuration conf)
List<org.apache.hadoop.mapreduce.InputSplit>	getSplits(org.apache.hadoop.mapreduce.JobContext context)
static void	setNumMapTasks(org.apache.hadoop.conf.Configuration conf, int numTasks)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

NMAPS_KEY

private static final String NMAPS_KEY

See Also:

• Constant Field Values

Constructor Details

NMapInputFormat

public NMapInputFormat()

Method Details

createRecordReader

public org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.NullWritable,org.apache.hadoop.io.NullWritable> createRecordReader(org.apache.hadoop.mapreduce.InputSplit split,
 org.apache.hadoop.mapreduce.TaskAttemptContext tac)

Specified by:

createRecordReader in class org.apache.hadoop.mapreduce.InputFormat<org.apache.hadoop.io.NullWritable,org.apache.hadoop.io.NullWritable>

getSplits

public List<org.apache.hadoop.mapreduce.InputSplit> getSplits(org.apache.hadoop.mapreduce.JobContext context)

Specified by:

getSplits in class org.apache.hadoop.mapreduce.InputFormat<org.apache.hadoop.io.NullWritable,org.apache.hadoop.io.NullWritable>

setNumMapTasks

public static void setNumMapTasks(org.apache.hadoop.conf.Configuration conf,
 int numTasks)

getNumMapTasks

public static int getNumMapTasks(org.apache.hadoop.conf.Configuration conf)