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.
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
PipeMapper
public PipeMapper()
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
Copyright © 2008 The Apache Software Foundation