Sakai MessageService

Info

The Sakai MessageService integrates JMS with Sakai and exposes the JMS API as a service. ActiveMQ is used as the JMS implementation.
Moire info about this related to events here: JMS Event Service

News

Source Code

https://source.sakaiproject.org/contrib/messageservice

Documentation JMS v1.1

Make sure that you look at the v1.1 and NOT v1.0.2 of the JMS API
- J2EE 1.4 Tutorial
  - Chapter 33 : JMS Tutorial
- JavaTM 2 Platform Enterprise Edition, v 1.4 API Specification
  - JMS v1.1 javax.jms

Usage

The MessageService API is very simple and exposes the following methods:


  /*
   * Creates a JMS connection with the default user identity. The connection is
   * created in stopped mode. No messages will be delivered until the
   * Connection.start method is explicitly called.
   *
   * @return a newly created JMS connection. May return null
   *
   */
   public Connection createConnection();

  /*
   * Creates a JMS connection with the specified user identity. The connection is
   * created in stopped mode. No messages will be delivered until the
   * Connection.start method is explicitly called.
   *
   * @parameter userName - the caller's user name
   * @parameter password - the caller's password
   *
   * @return a newly created JMS connection. May return null
   */
   public Connection createConnection(String userName, String password);

  /*
   * Gets the JMS Connection with the specified user identity, configured in components.xml
   * The connection is returned in start mode.
   *
   * @return the initially created JMS Connection object. May return null
   *
   */
   public Connection getConnection();

Usage with Spring (Sakai 2.5)


  <!-- definition of a message producer -->
  <bean id="org.sakaiproject.messageservice.test.MessageProducer"
    class="org.sakaiproject.messageservice.test.MessageProducerImpl">
      <property name="connectionFactory"
        ref="org.sakaiproject.messageservice.JmsConnectionFactory" />
      <property name="queueName" value="test.destination" />
  </bean>

  <!-- definition of listner container -->
  <bean id="listenerContainer"
    class="org.springframework.jms.listener.DefaultMessageListenerContainer"
    depends-on="org.sakaiproject.messageservice.JmsConnectionFactory">
      <property name="concurrentConsumers" value="1" />
      <property name="maxConcurrentConsumers" value="1" />
      <property name="connectionFactory"
        ref="org.sakaiproject.messageservice.JmsConnectionFactory" />
      <property name="destinationName" value="test.destination" />
      <!-- set pubSubDomain to false to create a queue instead of a Publish/Subscribe topic -->
      <property name="pubSubDomain" value="true"/>
      <property name="messageListener">
	<bean class="org.sakaiproject.messageservice.test.MessageListenerImpl"/>
      </property>
  </bean>

MessageService (JMS) Best Practices

JMS Connection Object
- Usually there is no need to create more than one JMS Connection object, and the ActiveMQ documentation and AQM Forum posts recommend to create/use only one connection object per server. Thus, in Sakai, we should use only one connection by calling getConnection(). In rare cases, it's justified to create a second connection.
JMS Session
- I asked about JMS session usage in the ActiveMQ forum, and here is the thread:
  - http://www.nabble.com/Using-one-session-per-message-to15114117s2354.html

Configuring

changing the persistence adapter
The persistence adapter can be changed in sakai.properties or local.properties.
property name:
targetBeanName@org.sakaiproject.messageservice.activemq.PersistenceAdapter
default value:
org.sakaiproject.messageservice.activemq.AMQPersistenceAdapter
possible persistence adapters:
org.sakaiproject.messageservice.activemq.AMQPersistenceAdapter
org.sakaiproject.messageservice.activemq.JournalPersistenceAdapter
org.sakaiproject.messageservice.activemq.JdbcPersistenceAdapter

enable clustered broker
By default the broker is configured to run in standalone mode. To enable a clustered environment and auto discovery the following change have to be applied to activemq-beans.xml
<bean id="org.sakaiproject.messageservice.JmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory"> <property name="brokerURL" value="discovery:(multicast://sakai)"/> </bean> <bean id="org.sakaiproject.messageservice.activemq.TransportConnector" class="org.apache.activemq.broker.TransportConnector" lazy-init="true"> <property name="name" value="default" /> <property name="uri" ref="org.sakaiproject.messageservice.api.BrokerUrl" /> <property name="discoveryUri" ref="org.sakaiproject.messageservice.api.DiscoveryUrl"/> </bean> <bean id="org.sakaiproject.messageservice.activemq.NetworkConnectorListFactory" class="org.springframework.beans.factory.config.BeanReferenceFactoryBean" lazy-init="true"> <property name="targetBeanName" value="org.sakaiproject.messageservice.activemq.DiscoveryNetworkConnectorList" /> </bean>

changing other Broker properties

On each application node, you need to enable the following ports and protocols in your host based firewall
- TCP port 61616
- UDP port 6155
- e.g. Linux iptables
  -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp -s 192.168.1.0/24 --dport 61616 -j ACCEPT -A RH-Firewall-1-INPUT -m state --state NEW -m udp -p udp -s 192.168.1.0/24 --dport 6155 -j ACCEPT

Building The MessageService sakai_2-4-x Branch (Maven 1)

svn co https://source.sakaiproject.org/contrib/messageservice/branches/sakai_2-4-x messageservice-2-4-x
cd messageservice-sakai_2-4-x
maven sakai