27.3. Using the Hadoop Connector

InfinispanInputFormat and InfinispanOutputFormat

In Hadoop, the InputFormat interface indicates how a specific data source is partitioned, along with how to read data from each of the partitions, while the OutputFormat interface specifies how to write data.

There are two methods of importance defined in the InpoutFormat interface: 
  • List<InputSplit> getSplits(JobContext context);
  • RecordReader<K,V> createRecordReader(InputSplit split,TaskAttemptContext context);
The getSplits method defines a data partitioner, returning one or more InputSplit instances that contain information regarding a certain section of the data. The InputSplit can then be used to obtain a RecordReader which will be used to iterate over the resulting dataset. These two operations allow for parallelization of data processing across multiple nodes, resulting in Hadoop's high throughput over large datasets.
In regards to JBoss Data Grid, partitions are generated based on segment ownership, meaning that each partition is a set of segments on a certain server. By default there will be as many partitions as servers in the cluster, and each partition will contain all segments associated with that specific server.
Running a Hadoop Map Reduce job on JBoss Data Grid

Example of configuring a Map Reduce job targeting a JBoss Data Grid cluster: 

import org.infinispan.hadoop.*;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Job;

[...]
Configuration configuration = new Configuration();
configuration.set(InfinispanConfiguration.INPUT_REMOTE_CACHE_SERVER_LIST, "localhost:11222");
configuration.set(InfinispanConfiguration.INPUT_REMOTE_CACHE_NAME, "map-reduce-in");
configuration.set(InfinispanConfiguration.OUTPUT_REMOTE_CACHE_SERVER_LIST, "localhost:11222");
configuration.set(InfinispanConfiguration.OUTPUT_REMOTE_CACHE_NAME, "map-reduce-out");

Job job = Job.getInstance(configuration, "Infinispan Integration");
[...]

In order to target the JBoss Data Grid, the job needs to be configured with the InfinispanInputFormat and InfinispanOutputFormat classes: 
[...]
// Define the Map and Reduce classes
job.setMapperClass(MapClass.class);
job.setReducerClass(ReduceClass.class);
  	
// Define the JBoss Data Grid implementations
job.setInputFormatClass(InfinispanInputFormat.class);
job.setOutputFormatClass(InfinispanOutputFormat.class);
[...]
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