spark-gremlin/src/main/java/org/apache/tinkerpop/gremlin/spark/structure/io/OutputFormatRDD.java

/*
 * 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.tinkerpop.gremlin.spark.structure.io;

import org.apache.commons.configuration2.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.tinkerpop.gremlin.hadoop.Constants;
import org.apache.tinkerpop.gremlin.hadoop.structure.io.ObjectWritable;
import org.apache.tinkerpop.gremlin.hadoop.structure.io.ObjectWritableIterator;
import org.apache.tinkerpop.gremlin.hadoop.structure.io.VertexWritable;
import org.apache.tinkerpop.gremlin.hadoop.structure.util.ConfUtil;
import org.apache.tinkerpop.gremlin.process.computer.KeyValue;
import scala.Tuple2;

import java.io.IOException;
import java.util.Collections;
import java.util.Iterator;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public final class OutputFormatRDD implements OutputRDD {

    @Override
    public void writeGraphRDD(final Configuration configuration, final JavaPairRDD<Object, VertexWritable> graphRDD) {
        final org.apache.hadoop.conf.Configuration hadoopConfiguration = ConfUtil.makeHadoopConfiguration(configuration);
        final String outputLocation = hadoopConfiguration.get(Constants.GREMLIN_HADOOP_OUTPUT_LOCATION);
        if (null != outputLocation) {
            // map back to a <nullwritable,vertexwritable> stream for output
            graphRDD.mapToPair(tuple -> new Tuple2<>(NullWritable.get(), tuple._2()))
                    .saveAsNewAPIHadoopFile(Constants.getGraphLocation(outputLocation),
                            NullWritable.class,
                            VertexWritable.class,
                            (Class<OutputFormat<NullWritable, VertexWritable>>) hadoopConfiguration.getClass(Constants.GREMLIN_HADOOP_GRAPH_WRITER, OutputFormat.class), hadoopConfiguration);
        }
    }

    @Override
    public <K, V> Iterator<KeyValue<K, V>> writeMemoryRDD(final Configuration configuration, final String memoryKey, JavaPairRDD<K, V> memoryRDD) {
        final org.apache.hadoop.conf.Configuration hadoopConfiguration = ConfUtil.makeHadoopConfiguration(configuration);
        final String outputLocation = hadoopConfiguration.get(Constants.GREMLIN_HADOOP_OUTPUT_LOCATION);
        if (null != outputLocation) {
            // map back to a Hadoop stream for output
            memoryRDD.mapToPair(keyValue -> new Tuple2<>(new ObjectWritable<>(keyValue._1()), new ObjectWritable<>(keyValue._2())))
                    .saveAsNewAPIHadoopFile(Constants.getMemoryLocation(outputLocation, memoryKey),
                            ObjectWritable.class,
                            ObjectWritable.class,
                            SequenceFileOutputFormat.class, hadoopConfiguration);
            try {
                return (Iterator) new ObjectWritableIterator(hadoopConfiguration, new Path(Constants.getMemoryLocation(outputLocation, memoryKey)));
            } catch (final IOException e) {
                throw new IllegalStateException(e.getMessage(), e);
            }
        }
        return Collections.emptyIterator();
    }
}