001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.activemq.broker.region.policy;
018
019 import java.util.ArrayList;
020 import java.util.List;
021 import org.apache.activemq.broker.Broker;
022 import org.apache.activemq.broker.ConnectionContext;
023 import org.apache.activemq.broker.region.MessageReference;
024 import org.apache.activemq.broker.region.SubscriptionRecovery;
025 import org.apache.activemq.broker.region.Topic;
026 import org.apache.activemq.command.ActiveMQDestination;
027 import org.apache.activemq.command.Message;
028 import org.apache.activemq.filter.DestinationFilter;
029
030 /**
031 * This implementation of {@link SubscriptionRecoveryPolicy} will keep a fixed
032 * count of last messages.
033 *
034 * @org.apache.xbean.XBean
035 *
036 */
037 public class FixedCountSubscriptionRecoveryPolicy implements SubscriptionRecoveryPolicy {
038 private volatile MessageReference messages[];
039 private int maximumSize = 100;
040 private int tail;
041
042 public SubscriptionRecoveryPolicy copy() {
043 FixedCountSubscriptionRecoveryPolicy rc = new FixedCountSubscriptionRecoveryPolicy();
044 rc.setMaximumSize(maximumSize);
045 return rc;
046 }
047
048 public synchronized boolean add(ConnectionContext context, MessageReference node) throws Exception {
049 messages[tail++] = node;
050 if (tail >= messages.length) {
051 tail = 0;
052 }
053 return true;
054 }
055
056 public synchronized void recover(ConnectionContext context, Topic topic, SubscriptionRecovery sub) throws Exception {
057 // Re-dispatch the last message seen.
058 int t = tail;
059 // The buffer may not have rolled over yet..., start from the front
060 if (messages[t] == null) {
061 t = 0;
062 }
063 // Well the buffer is really empty then.
064 if (messages[t] == null) {
065 return;
066 }
067 // Keep dispatching until t hit's tail again.
068 do {
069 MessageReference node = messages[t];
070 sub.addRecoveredMessage(context, node);
071 t++;
072 if (t >= messages.length) {
073 t = 0;
074 }
075 } while (t != tail);
076 }
077
078 public void start() throws Exception {
079 messages = new MessageReference[maximumSize];
080 }
081
082 public void stop() throws Exception {
083 messages = null;
084 }
085
086 public int getMaximumSize() {
087 return maximumSize;
088 }
089
090 /**
091 * Sets the maximum number of messages that this destination will hold
092 * around in RAM
093 */
094 public void setMaximumSize(int maximumSize) {
095 this.maximumSize = maximumSize;
096 }
097
098 public synchronized Message[] browse(ActiveMQDestination destination) throws Exception {
099 List<Message> result = new ArrayList<Message>();
100 DestinationFilter filter = DestinationFilter.parseFilter(destination);
101 int t = tail;
102 if (messages[t] == null) {
103 t = 0;
104 }
105 if (messages[t] != null) {
106 do {
107 MessageReference ref = messages[t];
108 Message message = ref.getMessage();
109 if (filter.matches(message.getDestination())) {
110 result.add(message);
111 }
112 t++;
113 if (t >= messages.length) {
114 t = 0;
115 }
116 } while (t != tail);
117 }
118 return result.toArray(new Message[result.size()]);
119 }
120
121 public void setBroker(Broker broker) {
122 }
123
124 }