Building a Stable and Clustered J2EE Environment?

royles asks: "I am working with several J2EE Application Servers and all seems fine until I start to scale and cluster. The goal is to ensure a web and EJB session is maintained across a pool of Application Servers. The level of complexity to achieve this straightforward requirement is proving too much. It quickly becomes evident that vendors claims of 'robust and scalable' go straight out the window in favour of extortionate support and consultant costs when the installation becomes large. Anybody else experienced this type of problem? What are other peoples experienceâ(TM)s in this area? Any recommendations on Application servers that âdo what they say on the tinâ(TM)? Any good online resources for achieving a highly scaled and robust solution?"

Comments

JBoss does this now

[GOD_ALMIGHTY]

First of all, do not store data on the application server. Secondly, make sure that all of your objects associated with a session in either the EJB layer or the HTTP session implement Serializable.

I'd recommend running JBoss + Tomcat on Linux with Apache frontending it with mod_jk2. Put all your static web content on Apache to free up Tomcat. The easiest way to do this is to use a load-balancing solution in front. Have it pass the sessions through to the Apache server which will offload any JSP/Servlet requests to Tomcat. Have the JBoss/Tomcat installation on each node of the cluster clustered using JBoss' JavaGroups based clustering. You can also use the JBoss Farm service to deploy the EAR file to one node in the cluster then have the other nodes pick it up from there.

If you use a seperate set of machines for the database cluster than the JBoss/Tomcat nodes can be set up as copies of each other with no data on board. Using Linux boxes, this is easy (dd the drives). If a node goes down for some reason, swap it with a spare. Any session info is already serialized and passed to the other nodes in the cluster, and the load-balancer w/ failover should handle the client end of that.

By the way this thing scales to at least 100 boxes from the stories I've heard. I've done it my self in small (5 box) installations. I've also used F5 equip for the load balancer/failover on the front. Everything worked well.

Buy the JBoss docs to help with the clustering. I've also got some docs I wrote on setting up JBoss clustering somewhere around here.

You'll be suprised how simple clustering is with JBoss once you understand a bit how JBoss works and is configured. You will also be amazed at how well it works.

The best part of course is that it's all Open Source, so no license fees. Hell, I'll set it up for you for 30% of the licenses and support you would have bought if you want. ;-)

Check out this article by Bill Burke

[jawahar]

Chief architect of JbossGroup

http://www.onjava.com/lpt/a/1517