The enterprise service bus (ESB) has found a home in the tool box of many modern architects, but it is still a young technology and implementation details can be daunting. It may seem counterintuitive, but enterprise service buses are still adding the capabilities that would mark them as enterprise-ready.
For many people, "SOA" is "ESB." But, the definition of ESB is a moving target—it started rather as a "three-ring binder" of accepted corporate integration practices, and now has taken the form of a service architecture that holds various middleware types. The term "bus" is used to allude to the hardware bus that connects chips on printed-circuit computer boards in the realm of hardware.
Messaging continues to be the primary service that ESBs provide, and many of them use Java as the language of choice. As with other Java undertakings, loading and unloading runtimes can be a job in itself.
One ESB is ServiceMix4, discussed by independent consultant Jeff Genender in a recent SearchSOA.com interview. In the story, entitled ''Software developers bring SOA apps into cloud computing architectures,'' Genender talks about issues of hot and cold swapping that have largely been addressed for computer hardware bus boards, but which still require a bit more magic on the software side. Genender tells developers that ServiceMix4 employs OSGi bundles that shield class loaders so some of the impact of deploying or un-deploying an ESB is mitigated. "It makes it so, as you deploy and un-deploy, the need to restart your instances is diminished," he said. Genender is among presenters on hand at TheServerSide Java Symposium in March in Las Vegas.
As indicated, ESBs are still relatively new technology. What happens when they come upon another new technology? A slightly more complex and different breed of challenges, perhaps. Or, alternatively, some improvements. Genender sees cloud as providing provisioning of services on the fly. It allows you to "bring up instances of ESB containers … you are also able to provision the actual services and bring them up or down," he said.
Related resources: ESB configuration drill-down info