org.apache.hadoop.hbase.mapreduce

Class MultithreadedTableMapper<K2,V2>

java.lang.Object

<any>

org.apache.hadoop.hbase.mapreduce.TableMapper<K2,V2>

org.apache.hadoop.hbase.mapreduce.MultithreadedTableMapper<K2,V2>

public class MultithreadedTableMapper<K2,V2>
extends TableMapper<K2,V2>

Multithreaded implementation for @link org.apache.hbase.mapreduce.TableMapper

It can be used instead when the Map operation is not CPU bound in order to improve throughput.

Mapper implementations using this MapRunnable must be thread-safe.

The Map-Reduce job has to be configured with the mapper to use via setMapperClass(Job, java.lang.Class<? extends <any>>) and the number of thread the thread-pool can use with the getNumberOfThreads(JobContext) method. The default value is 10 threads.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	MAPPER_CLASS
static java.lang.String	NUMBER_OF_THREADS

Constructor Summary

Constructors

Constructor and Description
MultithreadedTableMapper()

Method Summary

Modifier and Type	Method and Description
static <K2,V2> java.lang.Class<<any>>	getMapperClass(JobContext job) Get the application's mapper class.
static int	getNumberOfThreads(JobContext job) The number of threads in the thread pool that will run the map function.
void	run(Context context) Run the application's maps using a thread pool.
static <K2,V2> void	setMapperClass(Job job, java.lang.Class<? extends <any>> cls) Set the application's mapper class.
static void	setNumberOfThreads(Job job, int threads) Set the number of threads in the pool for running maps.

Methods inherited from class java.lang.Object

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

Field Detail

NUMBER_OF_THREADS

public static final java.lang.String NUMBER_OF_THREADS

See Also:

Constant Field Values

MAPPER_CLASS

public static final java.lang.String MAPPER_CLASS

See Also:

Constant Field Values

Constructor Detail

MultithreadedTableMapper

public MultithreadedTableMapper()

Method Detail

getNumberOfThreads

public static int getNumberOfThreads(JobContext job)

The number of threads in the thread pool that will run the map function.

Parameters:

job - the job

Returns:

the number of threads

setNumberOfThreads

public static void setNumberOfThreads(Job job,
                                      int threads)

Set the number of threads in the pool for running maps.

Parameters:

job - the job to modify

threads - the new number of threads

getMapperClass

public static <K2,V2> java.lang.Class<<any>> getMapperClass(JobContext job)

Get the application's mapper class.

Type Parameters:

K2 - the map's output key type

V2 - the map's output value type

Parameters:

job - the job

Returns:

the mapper class to run

setMapperClass

public static <K2,V2> void setMapperClass(Job job,
                                          java.lang.Class<? extends <any>> cls)

Set the application's mapper class.

Type Parameters:

K2 - the map output key type

V2 - the map output value type

Parameters:

job - the job to modify

cls - the class to use as the mapper

run

public void run(Context context)
         throws java.io.IOException,
                java.lang.InterruptedException

Run the application's maps using a thread pool.

Throws:

java.io.IOException

java.lang.InterruptedException