I'm starting a JEE project that needs to be strongly scalable. So far,
the concept was:
several Message Driven Beans, responsible for different parts of
the architecture
each MDB has a Session
Bean injected, handling
the business logic
a couple of Entity Beans, providing access to
the persistence layer
communication between
the different parts of
the architecture via Request/Reply concept via JMS messages:
MDB receives msg containing activity request
uses its session
bean to execute necessary business logic
returns response object in msg to original requester
The idea was that by de-coupling parts of
the architecture from each other via
the message bus, there is no limit to
the scalability. Simply start more components - as long as they are connected to
the same bus, we can grow and grow.
Unfortunately, we're having massive problems with
the request-reply concept. Transaction Mgmt seems to be in our way plenty. It seams that session beans are not supposed to consume messages?!
Reading http://blogs.sun.com/fkieviet/entry/request_reply_from_an_ejb and http://forums.sun.com/message.jspa?messageID=10338789, I get
the feeling that people actually recommend against
the request/reply concept for EJBs.
If that is
the case, how do you communicate between your EJBs? (Remember, scalability is what I'm after)
Details of my current setup:
MDB 1 'TestController', uses (local) SLSB 1 'TestService' for business logic
TestController.onMessage() makes TestService send a message to queue XYZ and requests a reply
TestService uses
Bean Managed Transactions
TestService establishes a connection & session to
the JMS broker via a joint connection factory upon initialization (@PostConstruct)
TestService commits
the transaction after sending, then begins another transaction and waits 10 sec for
the response
Message gets to MDB 2 'LocationController', which uses (local) SLSB 2 'LocationService' for business logic
LocationController.onMessage() makes LocationService send a message back to
the requested JMSReplyTo queue
Same BMT concept, same @PostConstruct concept
all use
the same connection factory to access
the broker
Problem:
The first message gets send (by SLSB 1) and received (by MDB 2) ok.
The sending of
the returning message (by SLSB 2) is fine as well. However, SLSB 1 never receives anything - it just times out.
I tried without
the messageSelector, no change, still no receiving message.
Is it not ok to consume message by a session bean?
SLSB 1 - TestService.java
@Resource(name = "jms/mvs.MVSControllerFactory")
private javax.jms.ConnectionFactory connectionFactory;
@PostConstruct
public void initialize() {
try {
jmsConnection = connectionFactory.createConnection();
session = jmsConnection.createSession(false, Session.AUTO_ACKNOWLEDGE);
System.out.println("Connection to JMS Provider established");
} catch (Exception e) { }
}
public Serializable sendMessageWithResponse(Destination reqDest, Destination respDest, Serializable request) {
Serializable response = null;
try {
utx.begin();
Random rand = new Random();
String correlationId = rand.nextLong() + "-" + (new Date()).getTime();
// prepare
the sending message object
ObjectMessage reqMsg = session.createObjectMessage();
reqMsg.setObject(request);
reqMsg.setJMSReplyTo(respDest);
reqMsg.setJMSCorrelationID(correlationId);
// prepare
the publishers and subscribers
MessageProducer producer = session.createProducer(reqDest);
// send
the message
producer.send(reqMsg);
System.out.println("Request Message has been sent!");
utx.commit();
// need to start second transaction, otherwise
the first msg never gets sent
utx.begin();
MessageConsumer consumer = session.createConsumer(respDest, "JMSCorrelationID = '" + correlationId + "'");
jmsConnection.start();
ObjectMessage respMsg = (ObjectMessage) consumer.receive(10000L);
utx.commit();
if (respMsg != null) {
response = respMsg.getObject();
System.out.println("Response Message has been received!");
} else {
// timeout waiting for response
System.out.println("Timeout waiting for response!");
}
} catch (Exception e) { }
return response;
}
SLSB 2 - LocationService.Java (only
the reply method, rest is same as above)
public boolean reply(Message origMsg, Serializable o) {
boolean rc = false;
try {
// check if we have necessary correlationID and replyTo destination
if (!origMsg.getJMSCorrelationID().equals("") && (origMsg.getJMSReplyTo() != null)) {
// prepare
the payload
utx.begin();
ObjectMessage msg = session.createObjectMessage();
msg.setObject(o);
// make it a response
msg.setJMSCorrelationID(origMsg.getJMSCorrelationID());
Destination dest = origMsg.getJMSReplyTo();
// send it
MessageProducer producer = session.createProducer(dest);
producer.send(msg);
producer.close();
System.out.println("Reply Message has been sent");
utx.commit();
rc = true;
}
} catch (Exception e) {}
return rc;
}
sun-resources.xml
<admin-object-resource enabled="true" jndi-name="jms/mvs.LocationControllerRequest" res-type="javax.jms.Queue" res-adapter="jmsra">
<property name="Name" value="mvs.LocationControllerRequestQueue"/>
</admin-object-resource>
<admin-object-resource enabled="true" jndi-name="jms/mvs.LocationControllerResponse" res-type="javax.jms.Queue" res-adapter="jmsra">
<property name="Name" value="mvs.LocationControllerResponseQueue"/>
</admin-object-resource>
<connector-connection-pool name="jms/mvs.MVSControllerFactoryPool" connection-definition-name="javax.jms.QueueConnectionFactory" resource-adapter-name="jmsra"/>
<connector-resource enabled="true" jndi-name="jms/mvs.MVSControllerFactory" pool-name="jms/mvs.MVSControllerFactoryPool" />
