pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/io/text/TextVertexInputFormat.java

/*
 * Copyright 2009-2010 by The Regents of the University of California
 * 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 from
 * 
 *     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 edu.uci.ics.pregelix.api.io.text;

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

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapreduce.InputSplit;
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.TextInputFormat;

import edu.uci.ics.pregelix.api.io.VertexInputFormat;
import edu.uci.ics.pregelix.api.io.VertexReader;

/**
 * Abstract class that users should subclass to use their own text based vertex
 * output format.
 * 
 * @param <I>
 *            Vertex index value
 * @param <V>
 *            Vertex value
 * @param <E>
 *            Edge value
 * @param <M>
 *            Message value
 */
@SuppressWarnings("rawtypes")
public abstract class TextVertexInputFormat<I extends WritableComparable, V extends Writable, E extends Writable, M extends Writable>
        extends VertexInputFormat<I, V, E, M> {
    /** Uses the TextInputFormat to do everything */
    protected TextInputFormat textInputFormat = new TextInputFormat();

    /**
     * Abstract class to be implemented by the user based on their specific
     * vertex input. Easiest to ignore the key value separator and only use key
     * instead.
     * 
     * @param <I>
     *            Vertex index value
     * @param <V>
     *            Vertex value
     * @param <E>
     *            Edge value
     */
    public static abstract class TextVertexReader<I extends WritableComparable, V extends Writable, E extends Writable, M extends Writable>
            implements VertexReader<I, V, E, M> {
        /** Internal line record reader */
        private final RecordReader<LongWritable, Text> lineRecordReader;
        /** Context passed to initialize */
        private TaskAttemptContext context;

        /**
         * Initialize with the LineRecordReader.
         * 
         * @param lineRecordReader
         *            Line record reader from TextInputFormat
         */
        public TextVertexReader(RecordReader<LongWritable, Text> lineRecordReader) {
            this.lineRecordReader = lineRecordReader;
        }

        @Override
        public void initialize(InputSplit inputSplit, TaskAttemptContext context) throws IOException,
                InterruptedException {
            lineRecordReader.initialize(inputSplit, context);
            this.context = context;
        }

        @Override
        public void close() throws IOException {
            lineRecordReader.close();
        }

        @Override
        public float getProgress() throws IOException, InterruptedException {
            return lineRecordReader.getProgress();
        }

        /**
         * Get the line record reader.
         * 
         * @return Record reader to be used for reading.
         */
        protected RecordReader<LongWritable, Text> getRecordReader() {
            return lineRecordReader;
        }

        /**
         * Get the context.
         * 
         * @return Context passed to initialize.
         */
        protected TaskAttemptContext getContext() {
            return context;
        }
    }

    @Override
    public List<InputSplit> getSplits(JobContext context, int numWorkers) throws IOException, InterruptedException {
        // Ignore the hint of numWorkers here since we are using TextInputFormat
        // to do this for us
        return textInputFormat.getSplits(context);
    }
}