EDIT

/**

 * Copyright (C) 2015 EDIT

 * European Distributed Institute of Taxonomy

 * http://www.e-taxonomy.eu

 *

 * The contents of this file are subject to the Mozilla Public License Version 1.1

 * See LICENSE.TXT at the top of this package for the full license terms.

 */

package eu.etaxonomy.cdm.server.instance;

import java.util.HashSet;

import java.util.LinkedList;

import java.util.Set;

import org.apache.log4j.Logger;

import org.eclipse.jetty.util.component.LifeCycle;

import org.eclipse.jetty.util.component.LifeCycle.Listener;

import org.slf4j.MDC;

import eu.etaxonomy.cdm.server.logging.InstanceLogWrapper;

/**

 * @author a.kohlbecker

 * @date Jul 29, 2015

 */

public class StartupQueue extends LinkedList<CdmInstance> {

    private static final long serialVersionUID = -8173521573512154767L;

    private final Logger logger = Logger.getLogger(InstanceManager.class);

    Set<CdmInstance> instancesStartingUp = new HashSet<>();

    private int parallelStartUps = 1;

    public int getParallelStartUps() {

        return parallelStartUps;

    }

    public void setParallelStartUps(int parallelStartUps) {

        this.parallelStartUps = parallelStartUps;

    }

    @Override

    public boolean add(CdmInstance e) {

        boolean result = super.add(e);

        registerAt(e);

        return result;

    }

    @Override

    public void addFirst(CdmInstance e) {

        super.addFirst(e);

        registerAt(e);

    }

    @Override

    public void addLast(CdmInstance e) {

        super.addLast(e);

        registerAt(e);

    }

    protected void notifyInstanceStartedUp(CdmInstance instance) {

        logger.debug("received message that instance " + instance.getName() + " has started up.");

        instancesStartingUp.remove(instance);

        startNextInstances();

    }

    protected void notifyInstanceFailed(CdmInstance instance) {

        logger.debug("received message that instance " + instance.getName() + " has failed.");

        instancesStartingUp.remove(instance);

        startNextInstances();

    }

    private void startNextInstances() {

        logger.debug("startNextInstances()");

        while(instancesStartingUp.size() < parallelStartUps && !isEmpty()) {

            CdmInstance nextInstance = pop();

            instancesStartingUp.add(nextInstance);

            logger.debug("Starting instance " + nextInstance.getName() + " in new thread.");

            Thread t = new StartupThread(nextInstance);

            t.start();

        }

    }

    @SuppressWarnings("unused")

    private void registerAt(CdmInstance e) {

        new InstanceListener(e);

        startNextInstances();

    }

    class InstanceListener implements Listener {

        private CdmInstance instance;

        InstanceListener(CdmInstance instance) {

            this.instance = instance;

            instance.getWebAppContext().addLifeCycleListener(this);

        }

        @Override

        public void lifeCycleStarting(LifeCycle event) {

            // IGNORE

        }

        @Override

        public void lifeCycleStarted(LifeCycle event) {

            notifyInstanceStartedUp(instance);

            // release reference to the instance so

            // that the thread can be garbage collected

            instance.getWebAppContext().removeLifeCycleListener(this);

            instance = null;

        }

        @Override

        public void lifeCycleFailure(LifeCycle event, Throwable cause) {

            notifyInstanceFailed(instance);

            // release reference to the instance so

            // that the thread can be garbage collected

            instance.getWebAppContext().removeLifeCycleListener(this);

            instance = null;

        }

        @Override

        public void lifeCycleStopping(LifeCycle event) {

            // IGNORE

        }

        @Override

        public void lifeCycleStopped(LifeCycle event) {

            // IGNORE

        }

    }

    class StartupThread extends Thread{

        private final Logger logger = Logger.getLogger(InstanceManager.class);

        private CdmInstance instance;

        StartupThread(CdmInstance instance){

            this.instance = instance;

        }

        @Override

        public void run() {

            try {

                MDC.put(InstanceLogWrapper.CDM_INSTANCE, instance.getName());

                instance.getWebAppContext().setThrowUnavailableOnStartupException(true);

                instance.getWebAppContext().start();

                // release reference to the instance so

                // that the thread can be garbage collected

                instance = null;

            } catch(InterruptedException e) {

                try {

                    instance.getWebAppContext().stop();

                } catch (Exception e1) {

                    logger.error("Error on stopping instance", e1);

                    notifyInstanceFailed(instance);

                }

            } catch (Throwable e) {

                logger.error("Could not start " + instance.getWebAppContext().getContextPath(), e);

                instance.getProblems().add(e.getMessage());

                instance.setStatus(Status.error);

                notifyInstanceFailed(instance);

                try {

                    // try to stop

                    instance.getWebAppContext().stop();

                } catch (Exception e1) {

                    /* IGNORE */

                }

            } finally {

                MDC.clear();

            }

        }

    }

}