org.apache.gora.mapreduce.GoraMapReduceUtils.java Source code

Introduction

Here is the source code for org.apache.gora.mapreduce.GoraMapReduceUtils.java

Source

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.gora.mapreduce;

import java.io.IOException;
import java.util.List;

import org.apache.gora.shims.hadoop.HadoopShim;
import org.apache.gora.shims.hadoop.HadoopShimFactory;
import org.apache.gora.util.StringUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

/**
 * MapReduce related utilities for Gora
 */
public class GoraMapReduceUtils {

    private static final HadoopShim hadoopShim = HadoopShimFactory.INSTANCE().getHadoopShim();

    public static class HelperInputFormat<K, V> extends FileInputFormat<K, V> {
        @Override
        public RecordReader<K, V> createRecordReader(InputSplit arg0, TaskAttemptContext arg1)
                throws IOException, InterruptedException {
            return null;
        }
    }

    /**
     * Add our own serializer (obtained via the {@link PersistentSerialization} 
     * wrapper) to any other <code>io.serializations</code> which may be specified 
     * within existing Hadoop configuration.
     * 
     * @param conf the Hadoop configuration object
     * @param reuseObjects boolean parameter to reuse objects
     */
    public static void setIOSerializations(Configuration conf, boolean reuseObjects) {
        String serializationClass = PersistentSerialization.class.getCanonicalName();
        String[] serializations = StringUtils.joinStringArrays(conf.getStrings("io.serializations"),
                "org.apache.hadoop.io.serializer.WritableSerialization",
                StringSerialization.class.getCanonicalName(), serializationClass);
        conf.setStrings("io.serializations", serializations);
    }

    public static List<InputSplit> getSplits(Configuration conf, String inputPath) throws IOException {
        JobContext context = createJobContext(conf, inputPath);

        HelperInputFormat<?, ?> inputFormat = new HelperInputFormat<Object, Object>();
        return inputFormat.getSplits(context);
    }

    public static JobContext createJobContext(Configuration conf, String inputPath) throws IOException {

        if (inputPath != null) {
            Job job = hadoopShim.createJob(conf);
            FileInputFormat.addInputPath(job, new Path(inputPath));
            return hadoopShim.createJobContext(job.getConfiguration());
        }

        return hadoopShim.createJobContext(conf);
    }
}