I have a JMS client which is producing messages and sending over a JMS queue to its unique consumer.
What I want is more than one consumer getting those messages. The first thing that comes to my mind is converting the queue to a topic, so current and new consumers can subscribe and get the same message delivered to all of them.
This will obviously involve modifying the current clients code in both producer and consumer side of things.
I would like to also look at other options like creating a second queue, so that I don't have to modify the existing consumer. I believe there are advantages in this approach like (correct me if I am wrong) balancing the load between two different queues rather than one, which might have a positive impact on performance.
I would like to get advise on these options and cons / pros that you might see. Any feedback is highly appreciated.
Best Answer
You have a few options as you stated.
If you convert it to a topic to get the same effect you will need to make the consumers persistent consumers. One thing the queue offers is persistence if your consumer isn't alive. This will depend on the MQ system you are using.
If you want to stick with queues, you will create a queue for each consumer and a dispatcher that will listen on the original queue.
Pros of Topics
Cons of Topics
Pros of Queues
Cons of Queues
When developing a Messaging System I prefer topics as it gives me the most power, but seeing as you are already using Queues it would require you to change how your system works to implement Topics instead.
Design and Implementation of Queue System with multiple consumers
Source
Keep in mind there are other things you'll need to take care of such as problem exception handling, reconnection to the connection and queues if you lose your connection, etc. This is just designed to give you an idea of how to accomplish what I described.
In a real system I probably wouldn't exit out at the first exception. I would allow the system to continue operating the best it could and log errors. As it stands in this code if putting a message in a single consumers queue fails, the whole dispatcher will stop.
Dispatcher.java
Main.java