SessionFactory.java

/*
 * Copyright 2009-2016 Tilmann Zaeschke. All rights reserved.
 * 
 * This file is part of ZooDB.
 * 
 * ZooDB 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.
 * 
 * ZooDB 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 ZooDB.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * See the README and COPYING files for further information. 
 */
package org.zoodb.internal.server;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;

import org.zoodb.internal.Node;
import org.zoodb.internal.client.AbstractCache;
import org.zoodb.internal.util.DBLogger;

/**
 * 
 * @author Tilmann Zaeschke
 */
public class SessionFactory {

	//TODO remove me
	@Deprecated
	public static boolean IGNORE_OPEN_SESSIONS = false;
	
	/**
	 * This is a hack to ensure that we don't use non-transactional read with multiple sessions.
	 */
	//TODO remove the following two!
	@Deprecated
	public static boolean FAIL_BECAUSE_OF_ACTIVE_NON_TX_READ = false;
	//TODO remove the following!
	@Deprecated
	public static boolean MULTIPLE_SESSIONS_ARE_OPEN = false;
	
	private static List<SessionManager> sessions = new ArrayList<>();
	
	public synchronized static DiskAccessOneFile getSession(Node node, AbstractCache cache) {
		String dbPath = node.getDbPath();
		DBLogger.debugPrintln(1, "Opening DB file: " + dbPath);

		Path path = FileSystems.getDefault().getPath(dbPath); 

		SessionManager sm = null;
		try {
			//TODO this does not scale
			for (SessionManager smi: sessions) {
				if (Files.isSameFile(smi.getPath(), path)) {
					sm = smi;
					break;
				}
			}
		} catch (IOException e) {
			throw DBLogger.newFatal("Failed while acessing path: " + dbPath, e);
		}

		if (sm == null) {
			//create DB file
			sm = new SessionManager(path);
			sessions.add(sm);
		} else {
			MULTIPLE_SESSIONS_ARE_OPEN = true;
			if (FAIL_BECAUSE_OF_ACTIVE_NON_TX_READ) {
				throw DBLogger.newFatal("Not supported: Can't use non-transactional read with "
						+ "mutliple sessions");
			}
		}
		
		return sm.createSession(node, cache);
	}
	
	static synchronized void removeSession(SessionManager sm) {
		//TODO this does not scale
		if (!sessions.remove(sm)) {
			throw DBLogger.newFatalInternal("Server session not found for: " + sm.getPath());
		}
		if (sessions.size() <= 1) {
			MULTIPLE_SESSIONS_ARE_OPEN = false;
		}
		if (sessions.isEmpty()) {
			FAIL_BECAUSE_OF_ACTIVE_NON_TX_READ = false;
		}
	}

	public synchronized static void clear() {
		sessions.clear();
		FAIL_BECAUSE_OF_ACTIVE_NON_TX_READ = false;
		MULTIPLE_SESSIONS_ARE_OPEN = false;
	}

	public static synchronized void cleanUp(File dbFile) {
		Path path = dbFile.toPath(); 

		try {
			//TODO this does not scale
			for (SessionManager smi: sessions) {
				if (Files.isSameFile(smi.getPath(), path)) {
					if (smi.isLocked() && !IGNORE_OPEN_SESSIONS) {
						throw DBLogger.newUser("Found open session on " + dbFile);
					}
					sessions.remove(smi);
					break;
				}
			}
			FAIL_BECAUSE_OF_ACTIVE_NON_TX_READ = false;
			MULTIPLE_SESSIONS_ARE_OPEN = false;
		} catch (IOException e) {
			throw DBLogger.newFatal("Failed while acessing path: " + dbFile, e);
		}
	}
}