JMS Provider Responsibilities For Concurrent Message Delivery

Question

Hi,
(This question pertains to the JMS api, outside a j2ee container)
Is it JMS-provider dependent on how concurrent message delivery is implemented? In other words, the code below sets up multiple consumers (on a topic), each with their own unique session and MessageListener and then a separate producer (with its own session) sends a message to the topic and I observer that only (4) onMessage() calls can execute concurrently. When one onMessage() method exits, that same thread gets assigned to execute another onMessage().
The only thing I could find on the matter in the spec was section in 4.4.15 Concurrent Message Delivery and it's pretty vague.
It's really important because of the acknowledgment mode. If it turns out that I need to delegate the real work that would be done in the onMessage() to another thread that I must manage (create, pool, etc), then once the onMessage() method completes (i.e., after it does the delegation to another thread), the message is deemed successfully consumed and will not be re-delivered again (and that's a problem if the custom thread fails for any reason). Of course, this assumes I'm using AUTO_ACKNOWLEDGE as the acknowledgment mode (which seems to make sense since using CLIENT_ACKNOWLEDGE mode will automatically acknowledge the receipt of all messages that have been consumed by the corresponding session and that's not good).
My JMS Provider is WL 9.1 and the trival sample code I'm using as my test follows below. I also show the ouput from running the example.
thanks for any help or suggestions,
mike
--- begin TopicExample.java ---
import java.io.*;
import java.util.*;
import javax.naming.*;
import javax.jms.*;
import javax.rmi.PortableRemoteObject;
class TopicExample {
public final static String JMS_PROVIDER_URL = "t3://localhost:8001";
public final static String JNDI_FACTORY="weblogic.jndi.WLInitialContextFactory";
public final static String JMS_FACTORY="CConFac";
public final static String TOPIC="CTopic";
public final static int NUM_CONSUMERS = 10;
public static void main(String[] args) throws Exception {
InitialContext ctx = getInitialContext(JMS_PROVIDER_URL);
ConnectionFactory jmsFactory;
Connection jmsConnection;
Session jmsReaderSession[] = new Session[10];
Session jmsWriterSession;
TextMessage jmsMessage;
Destination jmsDestination;
MessageProducer jmsProducer;
MessageConsumer jmsConsumer[] = new MessageConsumer[10];
MessageListener ml;
try
// Create connection
jmsFactory = (ConnectionFactory)
PortableRemoteObject.narrow(ctx.lookup(JMS_FACTORY), ConnectionFactory.class);
jmsConnection = jmsFactory.createConnection();
// Obtain topic
jmsDestination = (Destination) PortableRemoteObject.narrow(ctx.lookup(TOPIC), Destination.class);
// Reader session and consumer
for (int i=0; i<NUM_CONSUMERS; i++)
jmsReaderSession[i] = jmsConnection.createSession(false, Session.AUTO_ACKNOWLEDGE);
jmsConsumer[i] = jmsReaderSession.createConsumer(jmsDestination);
jmsConsumer[i].setMessageListener(
new MessageListener()
public void onMessage(Message msg) {
try {
String msgText;
if (msg instanceof TextMessage) {
msgText = ((TextMessage)msg).getText();
} else {
msgText = msg.toString();
System.out.println("JMS Message Received: "+ msgText );
System.out.println("press <return> to exit onMessage");
char c = getChar();
System.out.println("Exiting onMessage");
} catch (JMSException jmse) {
System.err.println("An exception occurred: "+jmse.getMessage());
// Writer session and producer
jmsWriterSession = jmsConnection.createSession(false, Session.AUTO_ACKNOWLEDGE);
jmsProducer = jmsWriterSession.createProducer(jmsDestination);
jmsMessage = jmsWriterSession.createTextMessage();
jmsMessage.setText("Hello World from Java!");
jmsConnection.start();
jmsProducer.send(jmsMessage);
char c = '\u0000';
while (!((c == 'q') || (c == 'Q'))) {
System.out.println("type q then <return> to exit main");
c = getChar();
for (int i=0; i<NUM_CONSUMERS; i++)
jmsReaderSession[i].close();
jmsWriterSession.close();
jmsConnection.close();
System.out.println("INFO: Completed normally");
} finally {
protected static InitialContext getInitialContext(String url)
throws NamingException
Hashtable<String,String> env = new Hashtable<String,String>();
env.put(Context.INITIAL_CONTEXT_FACTORY, JNDI_FACTORY);
env.put(Context.PROVIDER_URL, url);
return new InitialContext(env);
static public char getChar()
char ch = '\u0000';
try {
ch = (char) System.in.read();
System.out.flush();
} catch (IOException i) {
return ch;
--- end code --
Running the example:
prompt>java TopicExample
JMS Message Received: Hello World from Java!
JMS Message Received: Hello World from Java!
press <return> to exit onMessage
press <return> to exit onMessage
JMS Message Received: Hello World from Java!
press <return> to exit onMessage
JMS Message Received: Hello World from Java!
press <return> to exit onMessage
type q then <return> to exit main
[you see, only 4 onMessage() calls execute concurrently. Now I press <return>]
Exiting onMessage
JMS Message Received: Hello World from Java!
press <return> to exit onMessage
[now once the thread executing the onMessage() completes, the JMS providor assigns it to execute another onMessage() until all 10 onMessage() exections complete).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

Answer 1

I am too facing the same issue. but in my case I start getting this problem when the message size is about 1 MB itself.
Any help is appraciated.
Regards,
ved