Tomcat example source code file (ReplicatedMap.java)

This example Tomcat source code file (ReplicatedMap.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

channel, channelexception, classloader, io, mapmessage, member, member, membershiplistener, replicatedmap, replicatedmap, rpccallback, serializable, serializable, string, string

The Tomcat ReplicatedMap.java source code

/*
 * 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.catalina.tribes.tipis;

import java.io.Serializable;

import org.apache.catalina.tribes.Channel;
import org.apache.catalina.tribes.ChannelException;
import org.apache.catalina.tribes.ChannelListener;
import org.apache.catalina.tribes.Member;
import org.apache.catalina.tribes.MembershipListener;
import org.apache.catalina.tribes.group.RpcCallback;
import org.apache.catalina.tribes.tipis.AbstractReplicatedMap.MapOwner;

/**
 * All-to-all replication for a hash map implementation. Each node in the cluster will carry an identical 
 * copy of the map.<br>

 * This map implementation doesn't have a background thread running to replicate changes.
 * If you do have changes without invoking put/remove then you need to invoke one of the following methods:
 * <ul>
 * <li>replicate(Object,boolean) - replicates only the object that belongs to the key
 * <li>replicate(boolean) - Scans the entire map for changes and replicates data
 *  </ul>
 * the <code>boolean value in the replicate method used to decide
 * whether to only replicate objects that implement the <code>ReplicatedMapEntry interface
 * or to replicate all objects. If an object doesn't implement the <code>ReplicatedMapEntry interface
 * each time the object gets replicated the entire object gets serialized, hence a call to <code>replicate(true)
 * will replicate all objects in this map that are using this node as primary.
 *
 * <br>
REMBER TO CALL breakdown() or finalize() when you are done with the map to
 * avoid memory leaks.<br>

 * @todo implement periodic sync/transfer thread
 * @author Filip Hanik
 * @version 1.0
 * 
 * @todo memberDisappeared, should do nothing except change map membership
 *       by default it relocates the primary objects
 */
public class ReplicatedMap extends AbstractReplicatedMap implements RpcCallback, ChannelListener, MembershipListener {

    protected static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory.getLog(ReplicatedMap.class);

//------------------------------------------------------------------------------
//              CONSTRUCTORS / DESTRUCTORS
//------------------------------------------------------------------------------
    /**
     * Creates a new map
     * @param channel The channel to use for communication
     * @param timeout long - timeout for RPC messags
     * @param mapContextName String - unique name for this map, to allow multiple maps per channel
     * @param initialCapacity int - the size of this map, see HashMap
     * @param loadFactor float - load factor, see HashMap
     */
    public ReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, int initialCapacity,float loadFactor, ClassLoader[] cls) {
        super(owner,channel, timeout, mapContextName, initialCapacity, loadFactor, Channel.SEND_OPTIONS_DEFAULT, cls);
    }

    /**
     * Creates a new map
     * @param channel The channel to use for communication
     * @param timeout long - timeout for RPC messags
     * @param mapContextName String - unique name for this map, to allow multiple maps per channel
     * @param initialCapacity int - the size of this map, see HashMap
     */
    public ReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, int initialCapacity, ClassLoader[] cls) {
        super(owner,channel, timeout, mapContextName, initialCapacity, AbstractReplicatedMap.DEFAULT_LOAD_FACTOR,Channel.SEND_OPTIONS_DEFAULT, cls);
    }

    /**
     * Creates a new map
     * @param channel The channel to use for communication
     * @param timeout long - timeout for RPC messags
     * @param mapContextName String - unique name for this map, to allow multiple maps per channel
     */
    public ReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, ClassLoader[] cls) {
        super(owner, channel, timeout, mapContextName,AbstractReplicatedMap.DEFAULT_INITIAL_CAPACITY, AbstractReplicatedMap.DEFAULT_LOAD_FACTOR, Channel.SEND_OPTIONS_DEFAULT, cls);
    }

//------------------------------------------------------------------------------
//              METHODS TO OVERRIDE
//------------------------------------------------------------------------------
    protected int getStateMessageType() {
        return AbstractReplicatedMap.MapMessage.MSG_STATE_COPY;
    }
    
    /**
     * publish info about a map pair (key/value) to other nodes in the cluster
     * @param key Object
     * @param value Object
     * @return Member - the backup node
     * @throws ChannelException
     */
    protected Member[] publishEntryInfo(Object key, Object value) throws ChannelException {
        if  (! (key instanceof Serializable && value instanceof Serializable)  ) return new Member[0];
        //select a backup node
        Member[] backup = getMapMembers();

        if (backup == null || backup.length == 0) return null;

        //publish the data out to all nodes
        MapMessage msg = new MapMessage(getMapContextName(), MapMessage.MSG_COPY, false,
                                        (Serializable) key, (Serializable) value, null,channel.getLocalMember(false), backup);

        getChannel().send(getMapMembers(), msg, getChannelSendOptions());

        return backup;
    }

}