org.apache.giraph.examples
Class SimpleAggregatorWriter

java.lang.Object
  org.apache.giraph.conf.DefaultImmutableClassesGiraphConfigurable
      org.apache.giraph.examples.SimpleAggregatorWriter

All Implemented Interfaces:

AggregatorWriter, ImmutableClassesGiraphConfigurable

public class SimpleAggregatorWriter
extends DefaultImmutableClassesGiraphConfigurable
implements AggregatorWriter

This is a simple example for an aggregator writer. After each superstep the writer will persist the aggregator values to disk, by use of the Writable interface. The file will be created on the current working directory.

Field Summary

Fields inherited from interface org.apache.giraph.aggregators.AggregatorWriter

LAST_SUPERSTEP

Constructor Summary

SimpleAggregatorWriter()

Method Summary

void	close() The method is called at the end of a successful computation.
static String	getFilename()
void	initialize(org.apache.hadoop.mapreduce.Mapper.Context context, long applicationAttempt) The method is called at the initialization of the AggregatorWriter.
void	writeAggregator(Iterable<Map.Entry<String,org.apache.hadoop.io.Writable>> aggregatorMap, long superstep) The method is called at the end of each superstep.

Methods inherited from class org.apache.giraph.conf.DefaultImmutableClassesGiraphConfigurable

getConf, setConf

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.giraph.conf.ImmutableClassesGiraphConfigurable

getConf, setConf

Constructor Detail

SimpleAggregatorWriter

public SimpleAggregatorWriter()

Method Detail

getFilename

public static String getFilename()

initialize

public void initialize(org.apache.hadoop.mapreduce.Mapper.Context context,
                       long applicationAttempt)
                throws IOException

Description copied from interface: AggregatorWriter

The method is called at the initialization of the AggregatorWriter. More precisely, the aggregatorWriter is initialized each time a new master is elected.

Specified by:

initialize in interface AggregatorWriter

Parameters:

context - Mapper Context where the master is running on

applicationAttempt - ID of the applicationAttempt, used to disambiguate aggregator writes for different attempts

Throws:

IOException

writeAggregator

public void writeAggregator(Iterable<Map.Entry<String,org.apache.hadoop.io.Writable>> aggregatorMap,
                            long superstep)
                     throws IOException

Description copied from interface: AggregatorWriter

The method is called at the end of each superstep. The user might decide whether to write the aggregators values for the current superstep. For the last superstep, AggregatorWriter.LAST_SUPERSTEP is passed.

Specified by:

writeAggregator in interface AggregatorWriter

Parameters:

aggregatorMap - Map from aggregator name to aggregator value

superstep - Current superstep

Throws:

IOException

close

public void close()
           throws IOException

Description copied from interface: AggregatorWriter

The method is called at the end of a successful computation. The method is not called when the job fails and a new master is elected. For this reason it's advised to flush data at the end of AggregatorWriter.writeAggregator(Iterable, long).

Specified by:

close in interface AggregatorWriter

Throws:

IOException