clustermanager.java

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/**
 * $RCSfile: $
 * $Revision: $
 * $Date: $
 *
 * Copyright (C) 2008 Jive Software. All rights reserved.
 *
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution, or a commercial license
 * agreement with Jive.
 */

package org.jivesoftware.openfire.cluster;

import org.jivesoftware.openfire.XMPPServer;
import org.jivesoftware.util.JiveGlobals;
import org.jivesoftware.util.JiveProperties;
import org.jivesoftware.util.Log;
import org.jivesoftware.util.cache.CacheFactory;

import java.util.Collection;
import java.util.Queue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.LinkedBlockingQueue;

/**
 * A cluster manager is responsible for triggering events related to clustering.
 * A future version will also provide statistics about the cluster.
 *
 * @author Gaston Dombiak
 */
public class ClusterManager {
    public static String CLUSTER_PROPERTY_NAME = "clustering.enabled";
    private static Queue<ClusterEventListener> listeners = new ConcurrentLinkedQueue<ClusterEventListener>();
    private static BlockingQueue<Event> events = new LinkedBlockingQueue<Event>();

    static {
        Thread thread = new Thread("ClusterManager events dispatcher") {
            public void run() {
                for (; ;) {
                    try {
                        Event event = events.take();
                        EventType eventType = event.getType();
                        // Make sure that CacheFactory is getting this events first (to update cache structure)
                        if (eventType == EventType.joined_cluster && event.getNodeID() == null) {
                            // Replace standalone caches with clustered caches. Local cached data is not moved.
                            CacheFactory.joinedCluster();
                        }
                        // Now notify rest of the listeners
                        for (ClusterEventListener listener : listeners) {
                            try {
                                switch (eventType) {
                                    case joined_cluster: {
                                        if (event.getNodeID() == null) {
                                            listener.joinedCluster();
                                        }
                                        else {
                                            listener.joinedCluster(event.getNodeID());
                                        }
                                        break;
                                    }
                                    case left_cluster: {
                                        if (event.getNodeID() == null) {
                                            listener.leftCluster();
                                        }
                                        else {
                                            listener.leftCluster(event.getNodeID());
                                        }
                                        break;
                                    }
                                    case marked_senior_cluster_member: {
                                        listener.markedAsSeniorClusterMember();
                                        break;
                                    }
                                    default:
                                        break;
                                }
                            }
                            catch (Exception e) {
                                Log.error(e);
                            }
                        }
                        // Mark event as processed
                        event.setProcessed(true);
                    } catch (InterruptedException e) {
                        Log.warn(e);
                    } catch (Exception e) {
                        Log.error(e);
                    }
                }
            }
        };
        thread.setDaemon(true);
        thread.start();
    }

    /**
     * Registers a listener to receive events.
     *
     * @param listener the listener.
     */
    public static void addListener(ClusterEventListener listener) {
        if (listener == null) {
            throw new NullPointerException();
        }
        listeners.add(listener);
    }

    /**
     * Unregisters a listener to receive events.
     *
     * @param listener the listener.
     */
    public static void removeListener(ClusterEventListener listener) {
        listeners.remove(listener);
    }


    /**
     * Triggers event indicating that this JVM is now part of a cluster. At this point the
     * {@link org.jivesoftware.openfire.XMPPServer#getNodeID()} holds the new nodeID value and
     * the old nodeID value is passed in case the listener needs it.<p>
     * <p/>
     * When joining the cluster as the senior cluster member the {@link #fireMarkedAsSeniorClusterMember()}
     * event will be sent right after this event.<p>
     * <p/>
     * This event will be triggered in another thread. This will avoid potential deadlocks
     * in Coherence.
     *
     * @param asynchronous true if event will be triggered in background
     */
    public static void fireJoinedCluster(boolean asynchronous) {
        try {
            Event event = new Event(EventType.joined_cluster, null);
            events.put(event);
            if (!asynchronous) {
                while (!event.isProcessed()) {
                    Thread.sleep(50);
                }
            }
        } catch (InterruptedException e) {
            // Should never happen
            Log.error(e);
        }
    }

    /**
     * Triggers event indicating that another JVM is now part of a cluster.<p>
     *
     * This event will be triggered in another thread. This will avoid potential deadlocks
     * in Coherence.
     *
     * @param nodeID    nodeID assigned to the JVM when joining the cluster.
     * @param asynchronous true if event will be triggered in background
     */
    public static void fireJoinedCluster(byte[] nodeID, boolean asynchronous) {
        try {
            Event event = new Event(EventType.joined_cluster, nodeID);
            events.put(event);
            if (!asynchronous) {
                while (!event.isProcessed()) {
                    Thread.sleep(50);
                }
            }
        } catch (InterruptedException e) {
            // Should never happen
            Log.error(e);
        }
    }

    /**
     * Triggers event indicating that this JVM is no longer part of the cluster. This could
     * happen when disabling clustering support or removing the enterprise plugin that provides
     * clustering support.<p>
     *
     * Moreover, if we were in a "split brain" scenario (ie. separated cluster islands) and the
     * island were this JVM belonged was marked as "old" then all nodes of that island will
     * get the <tt>left cluster event</tt> and <tt>joined cluster events</tt>. That means that
     * caches will be reset and thus will need to be repopulated again with fresh data from this JVM.
     * This also includes the case where this JVM was the senior cluster member and when the islands
     * met again then this JVM stopped being the senior member.
     */
    public static void fireLeftCluster() {
        // Now notify rest of the listeners
        for (ClusterEventListener listener : listeners) {
            try {
                listener.leftCluster();
            }
            catch (Exception e) {
                Log.error(e);
            }
        }
    }

    /**
     * Triggers event indicating that another JVM is no longer part of the cluster. This could
     * happen when disabling clustering support or removing the enterprise plugin that provides
     * clustering support.
     *
     * @param nodeID    nodeID assigned to the JVM when joining the cluster.
     */
    public static void fireLeftCluster(byte[] nodeID) {
        try {
            Event event = new Event(EventType.left_cluster, nodeID);
            events.put(event);
        } catch (InterruptedException e) {
            // Should never happen
            Log.error(e);
        }
    }

    /**
     * Triggers event indicating that this JVM is now the senior cluster member. This
     * could either happen when initially joining the cluster or when the senior cluster
     * member node left the cluster and this JVM was marked as the new senior cluster member.<p>
     * <p/>
     * Moreover, in the case of a "split brain" scenario (ie. separated cluster islands) each
     * island will have its own senior cluster member. However, when the islands meet again there
     * could only be one senior cluster member so one of the senior cluster members will stop playing
     * that role. When that happens the JVM no longer playing that role will receive the
     * {@link #fireLeftCluster()} and {@link #fireJoinedCluster(boolean)} events.<p>
     * <p/>
     * This event will be triggered in another thread. This will avoid potential deadlocks
     * in Coherence.
     */
    public static void fireMarkedAsSeniorClusterMember() {
        try {
            events.put(new Event(EventType.marked_senior_cluster_member, null));
        } catch (InterruptedException e) {
            // Should never happen
        }
    }

    /**