org.apache.hadoop.streaming
Class PipeMapper

java.lang.Object
  org.apache.hadoop.streaming.PipeMapRed
      org.apache.hadoop.streaming.PipeMapper

All Implemented Interfaces:

Closeable, JobConfigurable, Mapper

public class PipeMapper
extends PipeMapRed
implements Mapper

A generic Mapper bridge. It delegates operations to an external program via stdin and stdout.

Field Summary

Fields inherited from class org.apache.hadoop.streaming.PipeMapRed

LOG, mapOutputFieldSeparator, numOfMapOutputKeyFields, numOfMapOutputPartitionFields, numOfReduceOutputKeyFields, outerrThreadsThrowable, reduceOutFieldSeparator

Constructor Summary

PipeMapper()

Method Summary

void	close()
void	configure(JobConf job) Initializes a new instance from a JobConf.
void	map(Object key, Object value, OutputCollector output, Reporter reporter) Maps a single input key/value pair into an intermediate key/value pair.

Methods inherited from class org.apache.hadoop.streaming.PipeMapRed

getContext, mapRedFinished

Methods inherited from class java.lang.Object

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

Constructor Detail

PipeMapper

public PipeMapper()

Method Detail

configure

public void configure(JobConf job)

Description copied from interface: JobConfigurable

Initializes a new instance from a JobConf.

Specified by:

configure in interface JobConfigurable

Overrides:

configure in class PipeMapRed

Parameters:

job - the configuration

map

public void map(Object key,
                Object value,
                OutputCollector output,
                Reporter reporter)
         throws IOException

Description copied from interface: Mapper

Maps a single input key/value pair into an intermediate key/value pair.

Output pairs need not be of the same types as input pairs. A given input pair may map to zero or many output pairs. Output pairs are collected with calls to OutputCollector.collect(Object,Object).

Applications can use the Reporter provided to report progress or just indicate that they are alive. In scenarios where the application takes an insignificant amount of time to process individual key/value pairs, this is crucial since the framework might assume that the task has timed-out and kill that task. The other way of avoiding this is to set mapred.task.timeout to a high-enough value (or even zero for no time-outs).

Specified by:

map in interface Mapper

Parameters:

key - the input key.

value - the input value.

output - collects mapped keys and values.

reporter - facility to report progress.

Throws:

IOException

close

public void close()

Specified by:

close in interface Closeable