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java.lang.Objectorg.apache.hadoop.streaming.PipeMapRed
org.apache.hadoop.streaming.PipeMapper
public class PipeMapper
A generic Mapper bridge. It delegates operations to an external program via stdin and stdout.
Field Summary |
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Fields inherited from class org.apache.hadoop.streaming.PipeMapRed |
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LOG, outerrThreadsThrowable |
Constructor Summary | |
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PipeMapper()
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Method Summary | |
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void |
close()
|
void |
configure(JobConf job)
Initializes a new instance from a JobConf . |
void |
map(java.lang.Object key,
java.lang.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 |
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getContext, mapRedFinished |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public PipeMapper()
Method Detail |
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public void configure(JobConf job)
JobConfigurable
JobConf
.
configure
in interface JobConfigurable
configure
in class PipeMapRed
job
- the configurationpublic void map(java.lang.Object key, java.lang.Object value, OutputCollector output, Reporter reporter) throws java.io.IOException
Mapper
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).
map
in interface Mapper
key
- the input key.value
- the input value.output
- collects mapped keys and values.reporter
- facility to report progress.
java.io.IOException
public void close()
close
in interface java.io.Closeable
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