What are my options in distributing a J2EE app on multiple servers?

I'm using JSP+Struts2+Tomcat6+Hibernate+MySQL as my J2EE developing environment. The first phase of the project has finished and it's up and running on a single server. due to growing scale of the website it's predicted that we're gonna face some performance issues in the future.

So we wanna distribute the application on several servers, What are 开发者_JAVA百科my options around here?

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Before optimize anything you should detect where your bottleneck is (Services, Database,...). If you do not do this, the optimization will be a waste of time and money.

And then the optimization is for example depending on you use case.

For example, if you have a read only application, add the bottleneck is both, Java Server and Database, then you can setup two database servers and two java servers.

Hardware is very important too. May the easiest way to to update the hardware. But this will only work if the hardware is the bottleneck.

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You can use any J2EE application server that supports clustering (e.g. WebLogic, WebSphere, JBoss, Tomcat). You are already using Tomcat so you may want use their clustering solution. Note that each offering provides different levels of clustering support so you should do some research before picking a particular app server (make sure it is the right clustering solution for your needs).

Also porting code from a standalone to a cluster environment often requires a non-negligible amount of development work. Among many other things you'll need to make sure that your application doesn't rely on any local files on the file system (this is a bad J2EE practice anyway), that state (HTTP sessions or stateful EJB - if any) gets properly propagated to all nodes in your cluster, etc. As a general rule, the more stateless, the smoother the transition to a cluster environment.

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As you are using Tomcat, I'd recommend to take a look at mod_cluster. But I suggest you to consider a real application server, like JBoss AS. Also, make sure to run some performance tests and understand where is the bottleneck of your application. Throwing more application servers is ineffective if, for instance, the bottleneck is at the database.