ConsumerFlowLimit set to 0 working incorrectly

Question

I've got a simple program which creates a queue and sets the consumerFlowLimit on that queue. Then it creates a producer for the queue which loads the queue with 10 messages. The payload of each message is the order it was created in. So the first message is a text message "1", the second message is a text message "2", etc.
The program then creates two consumers. The first is called "c5" because it reads a single message, prints the message, then sleeps for 5 seconds. The second is named "c1" because it does the same, but sleeps for only one second.
When I set consumerFlowLimit on the queue to -1 (unlimited) I get what I expect. The 10 messages get randomly "pre-assigned" to the queues, and I get output (something) like this:
c1 read message: 2 Mon Jul 14 08:37:53 PDT 2008
c5 read message: 1 Mon Jul 14 08:37:53 PDT 2008
c1 read message: 5 Mon Jul 14 08:37:54 PDT 2008
c1 read message: 7 Mon Jul 14 08:37:55 PDT 2008
c1 read message: 9 Mon Jul 14 08:37:56 PDT 2008
c5 read message: 3 Mon Jul 14 08:37:58 PDT 2008
c5 read message: 4 Mon Jul 14 08:38:03 PDT 2008
c5 read message: 6 Mon Jul 14 08:38:08 PDT 2008
c5 read message: 8 Mon Jul 14 08:38:13 PDT 2008
c5 read message: 10 Mon Jul 14 08:38:18 PDT 2008
What I want, however, is for the messages to be pulled off and printed in order, from 1 to 10. So I don't want the broker pre-assigning any of the messages -- I want the messages assigned to consumers only when they ask for them. So, I set the consumerFlowLimit to 0. But the setting of 0 behaves exactly like it does for the setting of -1. I think this is a bug and want to know if I should enter it as such. I see the same behavior for both the 1.3 and 1.4 brokers.
I do know that I'm successfully setting consumerFlowLimit, not only because I query and print it after I set it , but because when I set it to 1, it works as expected: only one message gets pre-assigned and output looks like this:
c5 read message: 1 Mon Jul 14 09:12:32 PDT 2008
c1 read message: 2 Mon Jul 14 09:12:32 PDT 2008
c1 read message: 4 Mon Jul 14 09:12:33 PDT 2008
c1 read message: 5 Mon Jul 14 09:12:34 PDT 2008
c1 read message: 6 Mon Jul 14 09:12:35 PDT 2008
c1 read message: 7 Mon Jul 14 09:12:36 PDT 2008
c5 read message: 3 Mon Jul 14 09:12:37 PDT 2008
c1 read message: 8 Mon Jul 14 09:12:37 PDT 2008
c1 read message: 10 Mon Jul 14 09:12:38 PDT 2008
c5 read message: 9 Mon Jul 14 09:12:42 PDT 2008
Thanks if you can help.

Answer 1

Challenge to Sun: Explain why there are no settings that allow this program to finish in 8 seconds every time it runs. 1 producer queues 10 messages. 2 consumers drain the queue. One sleeps 1 second after it dequeues a message, the other sleeps 5 seconds. Two messages should be dequeued at the 0 second marker and the 5 second marker, and one message at other second markers. 10 messages in 8 seconds. Should be easy, but openmq can't do it.
Command line looks like this once you compile it:
java -cp build\classes;lib\imqjmx.jar;lib\jms.jar;lib\imq.jar my.example.Flow 1 -1
The parameters are for the consumerFlowLimit and maxNumActiveConsumers attributes. Set them any way you like. Nothing will get you to 8 seconds consistently.
package my.example;
import java.util.Date;
import javax.jms.Connection;
import javax.jms.DeliveryMode;
import javax.jms.Destination;
import javax.jms.MessageConsumer;
import javax.jms.MessageProducer;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.management.Attribute;
import javax.management.MBeanServerConnection;
import javax.management.ObjectName;
import javax.management.remote.JMXConnector;
import com.sun.messaging.AdminConnectionFactory;
import com.sun.messaging.ConnectionConfiguration;
import com.sun.messaging.jms.management.server.DestinationAttributes;
import com.sun.messaging.jms.management.server.DestinationType;
import com.sun.messaging.jms.management.server.MQObjectName;
public class Flow {
private static com.sun.messaging.ConnectionFactory
connectionFactory = new com.sun.messaging.ConnectionFactory();
private String brokerName;
private int brokerPort;
private long flowLimit;
private int activeConsumers;
public Flow(String brokerName, int brokerPort, long flowLimit, int activeConsumers) {
this.brokerName = brokerName;
this.brokerPort = brokerPort;
this.flowLimit = flowLimit;
this.activeConsumers = activeConsumers;
public void start() {
try {
connectionFactory.setProperty(ConnectionConfiguration.imqAddressList,
this.brokerName + ":" + this.brokerPort);
Connection connection = connectionFactory.createConnection();
connection.start();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
String queueName = "myQueue";
Destination myQueue = session.createQueue(queueName);
MessageProducer producer = session.createProducer(myQueue);
producer.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
AdminConnectionFactory acf = new AdminConnectionFactory();
JMXConnector jmxc = acf.createConnection("admin", "admin");
MBeanServerConnection mbsc = jmxc.getMBeanServerConnection();
ObjectName destConfigName = MQObjectName.createDestinationConfig(DestinationType.QUEUE, queueName);
Attribute attr = new Attribute(DestinationAttributes.CONSUMER_FLOW_LIMIT, flowLimit);
mbsc.setAttribute(destConfigName, attr);
attr = new Attribute(DestinationAttributes.MAX_NUM_ACTIVE_CONSUMERS, activeConsumers);
mbsc.setAttribute(destConfigName, attr);
Long longAttrValue = (Long)mbsc.getAttribute(destConfigName, DestinationAttributes.CONSUMER_FLOW_LIMIT);
Integer attrValue = (Integer)mbsc.getAttribute(destConfigName, DestinationAttributes.MAX_NUM_ACTIVE_CONSUMERS);
jmxc.close();
System.out.println( "consumerFlowLimit: " + longAttrValue );
System.out.println( "maxNumActiveConsumers: " + attrValue);
// Pre-load the queue with 10 messages numbered from 1 to 10
for (int i = 1; i <= 10; i++) {
TextMessage message = session.createTextMessage();
message.setText(String.valueOf(i));
producer.send(message);
System.out.println("");
// Kick off two consumers
new Thread(new Consumer("c5", 5)).start();
new Thread(new Consumer("c1", 1)).start();
} catch (Exception e) {
System.out.println( "Exception occurred: " + e);
public static void main(String[] args) {
String limit = "1";
String activeConsumers = "-1";
if (args.length > 0) {
limit = args[0];
if (args.length > 1) {
activeConsumers = args[1];
Flow flow = new Flow("localhost", 7676, Long.parseLong(limit), Integer.parseInt(activeConsumers));
flow.start();
class Consumer implements Runnable {
private String name;
private int sleepSeconds;
public Consumer(String name, int sleepSeconds) {
this.name = name;
this.sleepSeconds = sleepSeconds;
public void run() {
try {
String queueName = "myQueue";
Connection connection = connectionFactory.createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
Destination myQueue = session.createQueue(queueName);
MessageConsumer consumer = session.createConsumer(myQueue);
connection.start();
while (true) {
TextMessage message = (TextMessage) consumer.receive();
System.out.println(this.name + " read message: " + message.getText() + "\t" + (new Date()));
Thread.sleep(sleepSeconds * 1000);
} catch (Exception e) {
System.out.println("Exception occurred: " + e);
}