replicatedmap.java

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/*
 * Copyright 1999,2004-2006 The Apache Software Foundation.
 *
 * Licensed 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 java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

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;

/**
 * All-to-all replication for a hash map implementation. Each node in the cluster will carry an identical 
 * copy of the map.<br><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><code>replicate(Object,boolean)</code> - replicates only the object that belongs to the key</li>
 * <li><code>replicate(boolean)</code> - Scans the entire map for changes and replicates data</li>
 *  </ul>
 * the <code>boolean</code> value in the <code>replicate</code> method used to decide
 * whether to only replicate objects that implement the <code>ReplicatedMapEntry</code> interface
 * or to replicate all objects. If an object doesn't implement the <code>ReplicatedMapEntry</code> interface
 * each time the object gets replicated the entire object gets serialized, hence a call to <code>replicate(true)</code>
 * will replicate all objects in this map that are using this node as primary.
 *
 * <br><br><b>REMBER TO CALL <code>breakdown()</code> or <code>finalize()</code> when you are done with the map to
 * avoid memory leaks.<br><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.commons.logging.Log log = org.apache.commons.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(Object 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(Object 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(Object 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
//------------------------------------------------------------------------------
    /**
     * 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 {
        //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_BACKUP, false,
                                        (Serializable) key, null, null, backup);

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

        return backup;
    }

    public Object get(Object key) {
        MapEntry entry = (MapEntry)super.get(key);
        if (entry == null) {
            return null;
        }
        return entry.getValue();
    }

    /**
     * Returns true if the key has an entry in the map.
     * The entry can be a proxy or a backup entry, invoking <code>get(key)</code>
     * will make this entry primary for the group
     * @param key Object
     * @return boolean
     */
    public boolean containsKey(Object key) {
        return super.containsKey(key);
    }

    public Object put(Object key, Object value) {
        if (! (key instanceof Serializable))throw new IllegalArgumentException("Key is not serializable:" +key.getClass().getName());
        if (value == null)return remove(key);
        if (! (value instanceof Serializable))throw new IllegalArgumentException("Value is not serializable:" +value.getClass().getName());

        MapEntry entry = new MapEntry( (Serializable) key, (Serializable) value);
        entry.setBackup(false);
        entry.setProxy(false);

        Object old = null;

        //make sure that any old values get removed
        if (containsKey(key)) old = remove(key);
        try {
            Member[] backup = publishEntryInfo(key, value);
            entry.setBackupNodes(backup);
        } catch (ChannelException x) {
            log.error("Unable to replicate out data for a LazyReplicatedMap.put operation", x);
        }
        super.put(key, entry);
        return old;
    }

    /**
     * Copies all values from one map to this instance
     * @param m Map
     * @todo send one bulk message
     */
    public void putAll(Map m) {
        Iterator i = m.entrySet().iterator();
        while (i.hasNext()) {
            Map.Entry entry = (Map.Entry) i.next();
            put(entry.getKey(), entry.getValue());
        }
    }

    /**
     * Removes an object from this map, it will also remove it from
     *
     * @param key Object
     * @return Object
     */
    public Object remove(Object key) {
        MapEntry entry = (MapEntry)super.remove(key);
        MapMessage msg = new MapMessage(getMapContextName(), MapMessage.MSG_REMOVE, false, (Serializable) key, null, null, null);
        try {
            getChannel().send(getMapMembers(), msg, Channel.SEND_OPTIONS_DEFAULT);
        } catch (ChannelException x) {
            log.error("Unable to replicate out data for a LazyReplicatedMap.remove operation", x);
        }
        return entry != null ? entry.getValue() : null;
    }

    public void clear() {
        //only delete active keys
        Iterator keys = keySet().iterator();
        while (keys.hasNext()) remove(keys.next());
    }

    public boolean containsValue(Object value) {
        if (value == null) {
            return super.containsValue(value);
        } else {
            Iterator i = super.entrySet().iterator();
            while (i.hasNext()) {
                Map.Entry e = (Map.Entry) i.next();
                MapEntry entry = (MapEntry) e.getValue();
                if ( value.equals(entry.getValue()) ) return true;
            } //while
            return false;
        } //end if
    }

    public Object clone() {
        throw new UnsupportedOperationException("This operation is not valid on a replicated map");
    }

    /**
     * Returns the entire contents of the map
     * Map.Entry.getValue() will return a LazyReplicatedMap.MapEntry object containing all the information
     * about the object.
     * @return Set
     */
    public Set entrySetFull() {
        return super.entrySet();
    }

    public Set keySetFull() {
        return super.keySet();
    }

    public Set entrySet() {
        LinkedHashSet set = new LinkedHashSet(super.size());
        Iterator i = super.entrySet().iterator();
        while (i.hasNext()) {
            Map.Entry e = (Map.Entry) i.next();
            MapEntry entry = (MapEntry) e.getValue();
            if (entry.isPrimary()) set.add(entry.getValue());
        }
        return Collections.unmodifiableSet(set);
    }

    public Set keySet() {
        //todo implement
        //should only return keys where this is active.
        LinkedHashSet set = new LinkedHashSet(super.size());
        Iterator i = super.entrySet().iterator();
        while (i.hasNext()) {
            Map.Entry e = (Map.Entry) i.next();
            MapEntry entry = (MapEntry) e.getValue();
            if (entry.isPrimary()) set.add(entry.getKey());
        }
        return Collections.unmodifiableSet(set);
    }

    public int sizeFull() {
        return super.size();
    }

    public int size() {
        return super.size();
    }

    protected boolean removeEldestEntry(Map.Entry eldest) {
        return false;
    }

    public boolean isEmpty() {
        return size() == 0;
    }

    public Collection values() {
        ArrayList values = new ArrayList(super.size());
        Iterator i = super.entrySet().iterator();
        while (i.hasNext()) {
            Map.Entry e = (Map.Entry) i.next();
            MapEntry entry = (MapEntry) e.getValue();
            values.add(entry);
        }
        return Collections.unmodifiableCollection(values);
    }

}