org.veronicadb.core.diskgraph.VDiskGraphShard.java Source code

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Here is the source code for org.veronicadb.core.diskgraph.VDiskGraphShard.java

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/*
 * Copyright 2015 Ambud Sharma
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.2
 */
package org.veronicadb.core.diskgraph;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ConcurrentHashMap;

import org.veronicadb.core.structures.ReadOnlyShardException;
import org.veronicadb.core.structures.ShardInitializationException;
import org.veronicadb.core.structures.VGraphShard;
import org.veronicadb.core.structures.VVertex;

import com.google.common.hash.BloomFilter;
import com.google.common.hash.Funnels;

public class VDiskGraphShard extends VGraphShard {

    private static final String CONFIG_STORAGE_DIRECTORY = "./target";
    private LinkedHashMap<String, VVertex> cache;
    private Map<Long, Long> vertexIndexHash;
    private BloomFilter<Long> shardBloom;
    private Queue<RandomAccessFile> fileReadPointers;
    private Set<Long> elementLocks;
    private String shardFileLocation;
    private MappedByteBuffer vertexIndex;
    private FileChannel indexChannel;

    public VDiskGraphShard(long shardId, int shardSize) {
        super(shardId, shardSize);
        this.shardBloom = BloomFilter.create(Funnels.longFunnel(), shardSize, 0.0001);
        this.cache = new LinkedHashMap<String, VVertex>((int) (shardSize / 0.40), 0.75f, true);
        this.shardFileLocation = CONFIG_STORAGE_DIRECTORY + "/" + shardId;
        this.fileReadPointers = new ArrayBlockingQueue<RandomAccessFile>(10, true);
        this.elementLocks = new HashSet<Long>();
        this.vertexIndexHash = new ConcurrentHashMap<Long, Long>(shardSize);
    }

    @Override
    public void init() throws ShardInitializationException {
        File shardFile = new File(shardFileLocation + ".dat");
        File indexFile = new File(shardFileLocation + ".idx");
        if (!shardFile.exists()) {
            try {
                shardFile.createNewFile();
            } catch (IOException e) {
                throw new ShardInitializationException(e);
            }
        }
        if (!indexFile.exists()) {
            try {
                indexFile.createNewFile();
            } catch (IOException e) {
                throw new ShardInitializationException(e);
            }
        }
        try {
            this.indexChannel = new RandomAccessFile(indexFile, "rw").getChannel();
            this.vertexIndex = this.indexChannel.map(MapMode.READ_WRITE, 0, this.indexChannel.size());
        } catch (IOException e) {
            throw new ShardInitializationException(e);
        }
        for (int i = 0; i < fileReadPointers.size(); i++) {
            RandomAccessFile filePointer = null;
            try {
                filePointer = new RandomAccessFile(shardFile, "r");
            } catch (FileNotFoundException e) {
                throw new ShardInitializationException(e);
            }
            fileReadPointers.add(filePointer);
        }
    }

    @Override
    public VVertex addVertex(String id, String label) throws ReadOnlyShardException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    protected void addVertex(VVertex vertex) throws ReadOnlyShardException {
    }

    public void updateElement() {
        // put element id in the locks set

    }

    @Override
    public VVertex getVertex(long vertexId) throws IOException {
        if (!vertexExists(vertexId)) {
            return null;
        } else {
            if (cache.containsKey(vertexId)) {
                return cache.get(vertexId);
            } else {
                // put data in the cache
                RandomAccessFile raf = fileReadPointers.poll();
                FileChannel channel = raf.getChannel();
                Long position = vertexIndexHash.get(vertexId);
                try {
                    channel.position(position);
                    ByteBuffer buffer = ByteBuffer.allocate(4);
                    channel.read(buffer);
                    int length = buffer.getInt();
                    buffer = ByteBuffer.allocate(length);
                    int next = 0;
                    do {
                        next = buffer.getInt();
                    } while (next != -1);

                } catch (IOException e) {
                    throw e;
                }
                return null;
            }
        }
    }

    @Override
    public boolean vertexExists(long vertexId) {
        if (shardBloom.mightContain(vertexId)) {
            if (cache.containsKey(vertexId)) {
                return true;
            } else {
                // actual file lookup
                return false;
            }
        } else {
            return false;
        }
    }

}