jena-fuseki2/jena-fuseki-webapp/src/main/java/org/apache/jena/fuseki/webapp/SystemState.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.jena.fuseki.webapp;

import org.apache.jena.atlas.lib.FileOps;
import org.apache.jena.fuseki.Fuseki;
import org.apache.jena.query.Dataset;
import org.apache.jena.tdb1.TDB1;
import org.apache.jena.tdb1.TDB1Factory;
import org.apache.jena.tdb1.base.block.FileMode;
import org.apache.jena.tdb1.base.file.Location;
import org.apache.jena.tdb1.setup.StoreParams;
import org.apache.jena.tdb1.sys.StoreConnection;
import org.apache.jena.tdb1.transaction.DatasetGraphTransaction;

/**
 * Small database to record the system state.
 * Used in the Full Fuseki server.
 */
public class SystemState {
    private static String SystemDatabaseLocation;
    // Testing may reset this.
    public static Location location;

    private  static Dataset                 dataset   = null;
    private  static DatasetGraphTransaction dsg       = null;

    public static Dataset getDataset() {
        init();
        return dataset;
    }

    public static DatasetGraphTransaction getDatasetGraph() {
        init();
        return dsg;
    }

    private static boolean initialized = false;
    private static void init() {
        init$();
    }

    /** Small footprint database.  The system database records the server state.
     * It should not be performance critical, mainly being used for system admin
     * functions.
     * <p>Direct mode so that it is not competing for OS file cache space.
     * <p>Small caches -
     */
    private static final StoreParams systemDatabaseParams = StoreParams.builder()
        .fileMode(FileMode.direct)
        .blockSize(1024)
        .blockReadCacheSize(50)
        .blockWriteCacheSize(20)
        .node2NodeIdCacheSize(500)
        .nodeId2NodeCacheSize(500)
        .nodeMissCacheSize(100)
        .build();

    public /* for testing */ static void init$() {
        if ( initialized )
            return;
        initialized = true;

        if ( location == null )
            location = Location.create(FusekiWebapp.dirSystemDatabase.toString());

        if ( ! location.isMem() )
            FileOps.ensureDir(location.getDirectoryPath());

        // Force it into the store connection as a low footprint
        if ( StoreConnection.getExisting(location) != null )
            Fuseki.serverLog.warn("System database already in the StoreConnection cache");
        StoreConnection.make(location, systemDatabaseParams);

        dataset = TDB1Factory.createDataset(location);
        dsg     = (DatasetGraphTransaction)(dataset.asDatasetGraph());
        dsg.getContext().set(TDB1.symUnionDefaultGraph, false);
    }
}