Scalability and high availability of a Java standalone application

Question

We are currently running a Java integration application on a Linux box. First an overview of the application.

The Java application is a standalone application (not deployed on any Java EE application server like OracleAS,WebLogic,JBOSS etc). By Stand Alone I mean its NOT a DESKTOP application. However it is run from the command line from a Main class. The user does not directly interact with this application at all. Messages are dumped into the queue using an API which is then read out by my Application which is constantly running 24/7. I wouldn't qualify this as a desktop app since the user has no direct interaction with it.(Not sure if this is the correct reasoning to qualify as one).

It uses Spring and connects to WebSphere MQ and Oracle Database We use a Spring Listener(Spring Message Driven POJOs) which listens to a queue on WebSphere MQ. Once there is a message in the queue, the application read the message from the MQ and dumps(insert/update) it into the database.

Now the question is:

1. How can we horizontally scale this application? I mean just putting more boxes and running multiple instances of this same application, is that a viable approach?
2. Should we consider moving from Spring MDPs to EJB MDBs? Thereby deploying it on the Application Server. Is there any added benefit by doing so?
3. There is a request to make the application High Available(HA)? What are the suggested methodologies or strategies that can be put in place to make a standalone application HA?

Answer 1

Another option is Terracotta, a framework that does precisely what you want; running your app on several machines simultaneously and balancing the load among them.