/*
* Copyright 2013 Alex Holmes
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.alexholmes.hadooputils.combine.avro.mapred;
import com.alexholmes.hadooputils.combine.common.mapred.CommonCombineRecordReader;
import com.alexholmes.hadooputils.combine.common.mapred.SplitMetricsCombineInputFormat;
import org.apache.avro.mapred.AvroOutputFormat;
import org.apache.avro.mapred.AvroRecordReader;
import org.apache.avro.mapred.AvroWrapper;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.mapred.lib.CombineFileInputFormat;
import org.apache.hadoop.mapred.lib.CombineFileSplit;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
* An {@link org.apache.hadoop.mapred.InputFormat} which can feed multiple
* input splits for Avro data files to individual mappers. This is useful in situations where you have a large
* number of Avro files that are at or smaller than the HDFS block size, and you wish to have a sensible
* cap on the number of reducers that run.
* <p/>
* Bear in mind that by default the {@link org.apache.hadoop.mapred.lib.CombineFileInputFormat} will only create a single input split
* for each node, which means only 1 mapper for the job will run on the node (under normal operating conditions).
* Therefore the default behavior impacts the mapper parallelism. You can cap the maximum number of
* bytes in an input split by either calling {@link org.apache.hadoop.mapred.lib.CombineFileInputFormat#setMaxSplitSize(long)},
* or by setting the configurable property {@code mapred.max.split.size}.
*
* @param <T> The type of the record in the Avro file.
*/
public class CombineAvroInputFormat<T> extends SplitMetricsCombineInputFormat<AvroWrapper<T>, NullWritable> {
@Override
protected FileStatus[] listStatus(JobConf job) throws IOException {
List<FileStatus> result = new ArrayList<FileStatus>();
for (FileStatus file : super.listStatus(job))
if (file.getPath().getName().endsWith(AvroOutputFormat.EXT))
result.add(file);
return result.toArray(new FileStatus[0]);
}
@Override
@SuppressWarnings("unchecked")
public RecordReader<AvroWrapper<T>, NullWritable>
getRecordReader(final InputSplit split, final JobConf job, final Reporter reporter)
throws IOException {
reporter.setStatus(split.toString());
return new CommonCombineRecordReader(job, (CombineFileSplit) split, new CommonCombineRecordReader.RecordReaderEngineerer() {
@Override
public RecordReader createRecordReader(Configuration conf, FileSplit split) throws IOException {
return new AvroRecordReader<T>(job, (FileSplit) split);
}
});
}
}