com.legstar.host.server.EngineHolder Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of legstar-distribution
Used to create a single distribution for the entire LegStar project.
The newest version!
/*******************************************************************************
 * Copyright (c) 2010 LegSem.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * 
 * Contributors:
 *     LegSem - initial API and implementation
 ******************************************************************************/
package com.legstar.host.server;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import javax.naming.InitialContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.legstar.config.PoolingEngineConfig;
import com.legstar.pool.manager.ConnectionPoolManager;
import com.legstar.work.invoke.InvokeWorkFactory;
import com.legstar.work.manager.WorkManagerImpl;

import commonj.work.WorkManager;

/**
 * This class holds a reference to a singleton Engine. Any client who needs
 * access to the engine will do so thru the engine holder.
 */
public final class EngineHolder {

    /** The singleton engine instance. */
    private static Engine sEngine;

    /** A thread pool to be used with default work manager implementation. */
    private static ExecutorService sExecutor;

    /** WorkManager implementation for asynchronous work. */
    private static WorkManager sWorkManager;

    /** Host connections pool manager. */
    private static ConnectionPoolManager sPoolManager;

    /** The current configuration settings. */
    private static PoolingEngineConfig sConfig;

    /** Logger. */
    private static final Log LOG = LogFactory.getLog(EngineHolder.class);

    /** An Engine Holder cannot be instantiated. */
    private EngineHolder() {
    }

    /**
     * Create the engine environment described in a configuration.
     * 
     * @param config the complete configuration hierarchy
     * @throws EngineConfigurationException if configuration is invalid
     */
    public static void preInit(final PoolingEngineConfig config)
            throws EngineConfigurationException {
        sConfig = config;
        sPoolManager = new ConnectionPoolManager(sConfig.getHostEndpoints());
        initializeWorkManager();
    }

    /**
     * Create the single instance of an engine.
     * 
     * @throws EngineStartupException if engine fails to start
     * */
    public static void init() throws EngineStartupException {
        LOG.debug("Starting engine.");
        sEngine = new Engine(sConfig.getMaxRequests(),
                sWorkManager,
                sPoolManager,
                new InvokeWorkFactory(),
                sConfig.getTakeTimeout());
        try {
            sWorkManager.schedule(sEngine, new EngineListener());
        } catch (IllegalArgumentException e) {
            throw new EngineStartupException(e);
        }
    }

    /** Shutdown the engine. */
    public static void stop() {
        if (sEngine != null) {
            sEngine.shutDown();
            sEngine = null;
        }
        if (sPoolManager != null) {
            sPoolManager.shutDown();
            sPoolManager = null;
        }
        if (sExecutor != null) {
            sExecutor.shutdownNow();
            sExecutor = null;
        }
        sWorkManager = null;
    }

    /**
     * @return the Engine singleton.
     * @throws EngineNotStartedException if engine is unavailable
     */
    public static Engine getEngine() throws EngineNotStartedException {
        if (sEngine == null) {
            throw new EngineNotStartedException(
                    "The host access engine is not running.");
        }
        if (sEngine.isShuttingDown()) {
            throw new EngineNotStartedException(
                    "The host access engine is shutting down.");
        }
        return sEngine;
    }

    /**
     * This method initializes the work manager used by the engine. We will
     * first attempt to lookup the work manager from the JNDI location
     * specified in the engine config file. If not specified, or unable to load,
     * we will use the default work manager.
     */
    private static void initializeWorkManager() {
        LOG.debug("Initializing Work Manager.");
        String workMgrLocation = sConfig.getWorkManagerJNDILocation();
        if (workMgrLocation != null && workMgrLocation.length() > 0) {
            try {
                InitialContext ic = new InitialContext();
                sWorkManager = (WorkManager) ic.lookup(workMgrLocation);
            } catch (Exception e) {
                sWorkManager = null;
            }
        } else {
            sWorkManager = null;
        }

        if (sWorkManager == null) {
            int threadPoolSize = sConfig.getThreadPoolSize();
            sExecutor = Executors.newFixedThreadPool(threadPoolSize);
            sWorkManager = new WorkManagerImpl(sExecutor);
        }
    }

}