public abstract class DataJoinMapperBase extends JobBase
Modifier and Type | Field and Description |
---|---|
protected java.lang.String |
inputFile |
protected org.apache.hadoop.io.Text |
inputTag |
protected JobConf |
job |
protected Reporter |
reporter |
Constructor and Description |
---|
DataJoinMapperBase() |
Modifier and Type | Method and Description |
---|---|
void |
close() |
void |
configure(JobConf job)
Initializes a new instance from a
JobConf . |
protected abstract org.apache.hadoop.io.Text |
generateGroupKey(TaggedMapOutput aRecord)
Generate a map output key.
|
protected abstract org.apache.hadoop.io.Text |
generateInputTag(java.lang.String inputFile)
Determine the source tag based on the input file name.
|
protected abstract TaggedMapOutput |
generateTaggedMapOutput(java.lang.Object value)
Generate a tagged map output value.
|
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.
|
void |
reduce(java.lang.Object arg0,
java.util.Iterator arg1,
OutputCollector arg2,
Reporter arg3)
Reduces values for a given key.
|
addDoubleValue, addLongValue, getDoubleValue, getLongValue, getReport, report, setDoubleValue, setLongValue
protected java.lang.String inputFile
protected JobConf job
protected org.apache.hadoop.io.Text inputTag
protected Reporter reporter
public void configure(JobConf job)
JobBase
JobConf
.configure
in interface JobConfigurable
configure
in class JobBase
job
- the configurationprotected abstract org.apache.hadoop.io.Text generateInputTag(java.lang.String inputFile)
inputFile
- protected abstract TaggedMapOutput generateTaggedMapOutput(java.lang.Object value)
value
- protected abstract org.apache.hadoop.io.Text generateGroupKey(TaggedMapOutput aRecord)
aRecord
- public 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).
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() throws java.io.IOException
java.io.IOException
public void reduce(java.lang.Object arg0, java.util.Iterator arg1, OutputCollector arg2, Reporter arg3) throws java.io.IOException
Reducer
The framework calls this method for each
<key, (list of values)>
pair in the grouped inputs.
Output values must be of the same type as input values. Input keys must
not be altered. The framework will reuse the key and value objects
that are passed into the reduce, therefore the application should clone
the objects they want to keep a copy of. In many cases, all values are
combined into zero or one value.
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).
arg0
- the key.arg1
- the list of values to reduce.arg2
- to collect keys and combined values.arg3
- facility to report progress.java.io.IOException
Copyright © 2009 The Apache Software Foundation