trunk/activemq-core/src/main/java/org/apache/activemq/broker/region/policy/FixedSizedSubscriptionRecoveryPolicy.java

/**
 * 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.activemq.broker.region.policy;

import java.util.Iterator;
import java.util.List;
import org.apache.activemq.broker.Broker;
import org.apache.activemq.broker.ConnectionContext;
import org.apache.activemq.broker.region.MessageReference;
import org.apache.activemq.broker.region.SubscriptionRecovery;
import org.apache.activemq.broker.region.Topic;
import org.apache.activemq.command.ActiveMQDestination;
import org.apache.activemq.command.Message;
import org.apache.activemq.memory.list.DestinationBasedMessageList;
import org.apache.activemq.memory.list.MessageList;
import org.apache.activemq.memory.list.SimpleMessageList;

/**
 * This implementation of {@link SubscriptionRecoveryPolicy} will keep a fixed
 * amount of memory available in RAM for message history which is evicted in
 * time order.
 * 
 * @org.apache.xbean.XBean
 * 
 */
public class FixedSizedSubscriptionRecoveryPolicy implements SubscriptionRecoveryPolicy {

    private MessageList buffer;
    private int maximumSize =  64 * 1024;
    private boolean useSharedBuffer = true;

    public FixedSizedSubscriptionRecoveryPolicy() {
        
    }
    
    public SubscriptionRecoveryPolicy copy() {
        FixedSizedSubscriptionRecoveryPolicy rc = new FixedSizedSubscriptionRecoveryPolicy();
        rc.setMaximumSize(maximumSize);
        rc.setUseSharedBuffer(useSharedBuffer);
        return rc;
    }

    public boolean add(ConnectionContext context, MessageReference message) throws Exception {
        buffer.add(message);
        return true;
    }

    public void recover(ConnectionContext context, Topic topic, SubscriptionRecovery sub) throws Exception {
        // Re-dispatch the messages from the buffer.
        List copy = buffer.getMessages(sub.getActiveMQDestination());
        if (!copy.isEmpty()) {
            for (Iterator iter = copy.iterator(); iter.hasNext();) {
                MessageReference node = (MessageReference)iter.next();
                sub.addRecoveredMessage(context, node);
            }
        }
    }

    public void start() throws Exception {
        buffer = createMessageList();
    }

    public void stop() throws Exception {
        buffer.clear();
    }

    // Properties
    // -------------------------------------------------------------------------
    public MessageList getBuffer() {
        return buffer;
    }

    public void setBuffer(MessageList buffer) {
        this.buffer = buffer;
    }

    public int getMaximumSize() {
        return maximumSize;
    }

    /**
     * Sets the maximum amount of RAM in bytes that this buffer can hold in RAM
     */
    public void setMaximumSize(int maximumSize) {
        this.maximumSize = maximumSize;
    }

    public boolean isUseSharedBuffer() {
        return useSharedBuffer;
    }

    public void setUseSharedBuffer(boolean useSharedBuffer) {
        this.useSharedBuffer = useSharedBuffer;
    }

    public Message[] browse(ActiveMQDestination destination) throws Exception {
        return buffer.browse(destination);
    }
    
    public void setBroker(Broker broker) {        
    }

    // Implementation methods

    // -------------------------------------------------------------------------
    protected MessageList createMessageList() {
        if (useSharedBuffer) {
            return new SimpleMessageList(maximumSize);
        } else {
            return new DestinationBasedMessageList(maximumSize);
        }
    }

}