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.advisory;
018
019 import java.util.concurrent.atomic.AtomicBoolean;
020 import java.util.concurrent.atomic.AtomicInteger;
021
022 import javax.jms.Connection;
023 import javax.jms.Destination;
024 import javax.jms.JMSException;
025 import javax.jms.Message;
026 import javax.jms.MessageConsumer;
027 import javax.jms.MessageListener;
028 import javax.jms.Session;
029
030 import org.apache.activemq.Service;
031 import org.apache.activemq.command.ActiveMQDestination;
032 import org.apache.activemq.command.ActiveMQMessage;
033 import org.apache.activemq.command.ActiveMQTopic;
034 import org.apache.activemq.command.ProducerId;
035 import org.apache.activemq.command.ProducerInfo;
036 import org.apache.activemq.command.RemoveInfo;
037 import org.slf4j.Logger;
038 import org.slf4j.LoggerFactory;
039
040 /**
041 * An object which can be used to listen to the number of active consumers
042 * available on a given destination.
043 *
044 *
045 */
046 public class ProducerEventSource implements Service, MessageListener {
047 private static final Logger LOG = LoggerFactory.getLogger(ProducerEventSource.class);
048
049 private final Connection connection;
050 private final ActiveMQDestination destination;
051 private ProducerListener listener;
052 private AtomicBoolean started = new AtomicBoolean(false);
053 private AtomicInteger producerCount = new AtomicInteger();
054 private Session session;
055 private MessageConsumer consumer;
056
057 public ProducerEventSource(Connection connection, Destination destination) throws JMSException {
058 this.connection = connection;
059 this.destination = ActiveMQDestination.transform(destination);
060 }
061
062 public void setProducerListener(ProducerListener listener) {
063 this.listener = listener;
064 }
065
066 public void start() throws Exception {
067 if (started.compareAndSet(false, true)) {
068 session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
069 ActiveMQTopic advisoryTopic = AdvisorySupport.getProducerAdvisoryTopic(destination);
070 consumer = session.createConsumer(advisoryTopic);
071 consumer.setMessageListener(this);
072 }
073 }
074
075 public void stop() throws Exception {
076 if (started.compareAndSet(true, false)) {
077 if (session != null) {
078 session.close();
079 }
080 }
081 }
082
083 public void onMessage(Message message) {
084 if (message instanceof ActiveMQMessage) {
085 ActiveMQMessage activeMessage = (ActiveMQMessage)message;
086 Object command = activeMessage.getDataStructure();
087 int count = 0;
088 if (command instanceof ProducerInfo) {
089 count = producerCount.incrementAndGet();
090 count = extractProducerCountFromMessage(message, count);
091 fireProducerEvent(new ProducerStartedEvent(this, destination, (ProducerInfo)command, count));
092 } else if (command instanceof RemoveInfo) {
093 RemoveInfo removeInfo = (RemoveInfo)command;
094 if (removeInfo.isProducerRemove()) {
095 count = producerCount.decrementAndGet();
096 count = extractProducerCountFromMessage(message, count);
097 fireProducerEvent(new ProducerStoppedEvent(this, destination, (ProducerId)removeInfo.getObjectId(), count));
098 }
099 } else {
100 LOG.warn("Unknown command: " + command);
101 }
102 } else {
103 LOG.warn("Unknown message type: " + message + ". Message ignored");
104 }
105 }
106
107 protected int extractProducerCountFromMessage(Message message, int count) {
108 try {
109 Object value = message.getObjectProperty("producerCount");
110 if (value instanceof Number) {
111 Number n = (Number)value;
112 return n.intValue();
113 }
114 LOG.warn("No producerCount header available on the message: " + message);
115 } catch (Exception e) {
116 LOG.warn("Failed to extract producerCount from message: " + message + ".Reason: " + e, e);
117 }
118 return count;
119 }
120
121 protected void fireProducerEvent(ProducerEvent event) {
122 if (listener != null) {
123 listener.onProducerEvent(event);
124 }
125 }
126
127 }