Setting MessageProducer priority has no effect on messages - spring-boot

Question

I have high priority messages that needs to be processed over lower priority messages, but setting the priority on MessageProducer seems to have no impact and the messages are consumed in the same order as they are sent to queue.
Below is my code:
package com.example.jms;
import javax.jms.ConnectionFactory;
import javax.jms.DeliveryMode;
import javax.jms.JMSException;
import javax.jms.MessageProducer;
import javax.jms.Session;
import javax.jms.TextMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jms.DefaultJmsListenerContainerFactoryConfigurer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.jms.config.DefaultJmsListenerContainerFactory;
import org.springframework.jms.config.JmsListenerContainerFactory;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.jms.core.ProducerCallback;
import org.springframework.jms.support.converter.MappingJackson2MessageConverter;
import org.springframework.jms.support.converter.MessageConverter;
import org.springframework.jms.support.converter.MessageType;
#SpringBootApplication
public class JmsPriorityApplication {
private static final Logger logger= LoggerFactory.getLogger(JmsPriorityApplication.class);
public static void main(String[] args) {
// Launch the application
ConfigurableApplicationContext context = SpringApplication.run(JmsPriorityApplication.class, args);
JmsTemplate jmsTemplate = context.getBean(JmsTemplate.class);
// Send a message with a POJO - the template reuse the message converter
System.out.println("Sending an email message.");
jmsTemplate.execute("mailbox", new ProducerCallback<Object>() {
#Override
public Object doInJms(Session session, MessageProducer producer) throws JMSException {
String text = "Hello this msg1";
int priority=1;
TextMessage message1 = session.createTextMessage(text);
producer.send(message1, DeliveryMode.PERSISTENT, priority, 0);
logger.info("{} sent with priority={}", text, priority);
text = "Hello this msg2";
priority=9;
TextMessage message2 = session.createTextMessage(text);
producer.send(message2, DeliveryMode.PERSISTENT, priority, 0);
logger.info("{} sent with priority={}", text, priority);
return null;
}
} );
}
#Bean
public JmsListenerContainerFactory<?> myFactory(ConnectionFactory connectionFactory,
DefaultJmsListenerContainerFactoryConfigurer configurer) {
DefaultJmsListenerContainerFactory factory = new DefaultJmsListenerContainerFactory();
// This provides all boot's default to this factory, including the message converter
configurer.configure(factory, connectionFactory);
// You could still override some of Boot's default if necessary.
return factory;
}
}
Receiver.java
package com.example.jms;
import org.springframework.jms.annotation.JmsListener;
import org.springframework.stereotype.Component;
#Component
public class Receiver {
#JmsListener(destination = "mailbox", containerFactory = "myFactory")
public void receiveMessage(String msg) {
System.out.println("Received <" + msg + ">");
}
}
Below is the output:
Sending an email message.
2019-02-05 17:42:44.161 INFO 7828 --- [ main] com.example.jms.JmsPriorityApplication : Hello this msg1 sent with priority=1
2019-02-05 17:42:44.161 INFO 7828 --- [ main] com.example.jms.JmsPriorityApplication : Hello this msg2 sent with priority=9
Received <Hello this msg1>
Received <Hello this msg2>
I was expecting msg2 to be received before msg1. I am not sure what I am missing here. Note: the consumer is active while messages are being sent.

Answer 1

Since the consumer is active when the messages are being sent it's almost certain that the broker is dispatching the first message to the client before the second one arrives on the broker. This means that there's basically no time for the higher priority message to preempt the lower priority message since the client has already received the lower priority message.
In general, the idea of prioritized delivery only makes sense when there is a build-up of messages in the queue. For your test you should either not activate the consumer until all the messages have been sent (a task that would require some kind of external coordination or manual intervention) or increase the message volume so that enough messages build up in the queue the prioritized delivery can actually happen.