org.neo4j.kernel.api.impl.index.LuceneSnapshotter.java Source code

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Here is the source code for org.neo4j.kernel.api.impl.index.LuceneSnapshotter.java

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/**
 * Copyright (c) 2002-2014 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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/>.
 */
package org.neo4j.kernel.api.impl.index;

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

import org.apache.lucene.index.IndexCommit;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.SnapshotDeletionPolicy;
import org.neo4j.graphdb.ResourceIterator;
import org.neo4j.helpers.collection.PrefetchingIterator;

import static org.neo4j.helpers.collection.IteratorUtil.emptyIterator;

public class LuceneSnapshotter {
    private static final String NO_INDEX_COMMIT_TO_SNAPSHOT = "No index commit to snapshot";
    private static final String ID = "backup";

    ResourceIterator<File> snapshot(File indexDir, IndexWriter writer) throws IOException {
        SnapshotDeletionPolicy deletionPolicy = (SnapshotDeletionPolicy) writer.getConfig()
                .getIndexDeletionPolicy();

        try {
            return new LuceneSnapshotIterator(indexDir, deletionPolicy.snapshot(ID), deletionPolicy);
        } catch (IllegalStateException e) {
            if (e.getMessage().equals(NO_INDEX_COMMIT_TO_SNAPSHOT)) {
                return emptyIterator();
            }
            throw e;
        }
    }

    private class LuceneSnapshotIterator extends PrefetchingIterator<File> implements ResourceIterator<File> {
        private final File indexDirectory;
        private final SnapshotDeletionPolicy deletionPolicy;
        private Iterator<String> fileNames;

        LuceneSnapshotIterator(File indexDirectory, IndexCommit snapshotPoint,
                SnapshotDeletionPolicy deletionPolicy) throws IOException {
            this.indexDirectory = indexDirectory;
            this.deletionPolicy = deletionPolicy;
            this.fileNames = snapshotPoint.getFileNames().iterator();
        }

        @Override
        protected File fetchNextOrNull() {
            if (!fileNames.hasNext()) {
                return null;
            }
            return new File(indexDirectory, fileNames.next());
        }

        @Override
        public void close() {
            try {
                deletionPolicy.release(ID);
            } catch (IOException e) {
                // TODO What to do here?
                throw new RuntimeException("Unable to close lucene index snapshot", e);
            }
        }
    }

}