Package ml.shifu.guagua.mapreduce

Class GuaguaMRRecordReader

java.lang.Object

org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

ml.shifu.guagua.mapreduce.GuaguaMRRecordReader

All Implemented Interfaces:

Closeable, AutoCloseable

public class GuaguaMRRecordReader
extends org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

GuaguaMRRecordReader is used as a mock for mapreduce reader interface, not real reading data.

To update progress, currentIteration and totalIterations should be set. currentIteration only can be set in GuaguaMapper.run.

Why set currentIteration to static? The reason is that currentIteration for task cannot be transferred to #GuaguaRecordReader because of no API from MapperContext. So static field here is used to update current iteration.

If currentIteration is not set in each iteration. It can only start from 0. This progress update doesn't work well for task fail-over(TODO).

Constructor Summary

Constructors

Constructor	Description
GuaguaMRRecordReader()	Default constructor, totalIterations is set to default 0.
GuaguaMRRecordReader(int totalIterations)	Constructor with totalIterations setting.

Method Summary

Modifier and Type	Method	Description
void	close()
org.apache.hadoop.io.LongWritable	getCurrentKey()	This is a mock to hide Hadoop raw map iteration on map input key.
org.apache.hadoop.io.Text	getCurrentValue()	This is a mock to hide Hadoop raw map iteration on map input value.
float	getProgress()	Each iteration context.nextKeyValue should be called, and currentIteration is updated, so the progress is updated.
void	initialize(org.apache.hadoop.mapreduce.InputSplit inputSplit, org.apache.hadoop.mapreduce.TaskAttemptContext context)
boolean	nextKeyValue()	Update iteration number.
static void	setCurrentIteration(int currentIteration)	Should only be called in GuaguaMapper Progress callback.

Methods inherited from class java.lang.Object

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

Constructor Detail

GuaguaMRRecordReader

public GuaguaMRRecordReader()

Default constructor, totalIterations is set to default 0.

GuaguaMRRecordReader

public GuaguaMRRecordReader(int totalIterations)

Constructor with totalIterations setting.

Parameters:

totalIterations - total iterations for such guagua job.

Method Detail

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

Throws:

IOException

getProgress

public float getProgress()
                  throws IOException

Each iteration context.nextKeyValue should be called, and currentIteration is updated, so the progress is updated.

Specified by:

getProgress in class org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

Throws:

IOException

getCurrentKey

public org.apache.hadoop.io.LongWritable getCurrentKey()
                                                throws IOException,
                                                       InterruptedException

This is a mock to hide Hadoop raw map iteration on map input key.

Specified by:

getCurrentKey in class org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

Throws:

IOException

InterruptedException

getCurrentValue

public org.apache.hadoop.io.Text getCurrentValue()
                                          throws IOException,
                                                 InterruptedException

This is a mock to hide Hadoop raw map iteration on map input value.

Specified by:

getCurrentValue in class org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

Throws:

IOException

InterruptedException

initialize

public void initialize(org.apache.hadoop.mapreduce.InputSplit inputSplit,
                       org.apache.hadoop.mapreduce.TaskAttemptContext context)
                throws IOException,
                       InterruptedException

Specified by:

initialize in class org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

Throws:

IOException

InterruptedException

nextKeyValue

public boolean nextKeyValue()
                     throws IOException,
                            InterruptedException

Update iteration number. This is called for each iteration once. It is used to update Hadoop job progress more precisely.

Specified by:

nextKeyValue in class org.apache.hadoop.mapreduce.RecordReader<org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.Text>

Throws:

IOException

InterruptedException

setCurrentIteration

public static void setCurrentIteration(int currentIteration)

Should only be called in GuaguaMapper Progress callback.