Even though the dust hasn't settled around an exact definition of an enterprise service bus (ESB), there are several open source efforts forging ahead. Most recently, the ObjectWeb consortium released Milestone 1 of Celtix, an open source ESB sponsored by Iona Technologies. At the same time, ObjectWeb and Iona announced cooperation between Celtix and ServiceMix, an open source ESB supported by LogicBlaze Inc., a provider of open source integration technology and services.
Iona and ObjectWeb launched the Celtix project in June. "Milestone 1 is a top-to-bottom demonstration of Web services and APIs," said Carl Trieloff, director of product management at Iona. "When we get to Milestone 2, you should be able to start having more ESB-type interactions." He said the project intends to release milestones about every four weeks.
The ServiceMix project was launched this summer, and the first release was available in August. The underlying technology is based on ActiveMQ, LogicBlaze's open source message queue product. ServiceMix was built around the Java Business Integration (JBI) specification JSR 208.
According to Tom Miura, CEO of Marina del Rey, Calif.-based LogicBlaze, ServiceMix and Celtix "took different approaches to the ESB problem. We looked at it from a JBI standpoint. They looked at it from their heritage to solve problems through brokers and adapters. By coming together, the two technologies can serve a larger market. We will support each other, and we may end up committing code to each other."
Trieloff said participants from both projects have been active on each other's mailing lists, but are not committers at this point. By cooperating, Celtix will be able to take advantage of several ServiceMix capabilities, such as "binding for Groovy, binding for ActiveMQ and interacting with Spring," Trieloff said. In return, Celtix can offer ServiceMix "HTTP, reliable messaging, a transport binding mechanism, the container aspect, some of the routing aspects, etc. These are some of the areas they're interested in offering back to their customers."
Both Iona and LogicBlaze are also participating in the Apache Synapse project, an open source Web service mediation framework launched in August. The Synapse participants chose not to call the effort an ESB, "but it certainly looks like one," said Tom Rhinelander, principal industry analyst, New Rowley Group Inc., Georgetown, Mass. "At this point people agree you need something in the middle of the service-oriented architecture."
IDC, Framingham, Mass., last month interviewed 20 vendors and "got 10 different definitions of ESBs," said Dennis Byron, a vice president at IDC. "The one consistency is no one really wants to sell the thing freestanding; IBM just announced it will, but it really pushes people toward the integration broker. BEA sort of announced it will, but it's really pushing the whole AquaLogic platform. But none will claim the real market is in selling this thing freestanding. It's got to be part of an integration platform for SOA."
As has been the trend with open source projects, all vendors with stakes in this area will have to watch which, if any, ESB gains momentum. "Take IBM as an example of trend," Byron said. "If for whatever reason the ObjectWeb [ESB], for example, becomes hugely popular in the market, like the Apache Web server, I don't think they'd hesitate [to support it]."
But New Rowley Group's Rhinelander doesn't think the major vendors will look to support three open source ESBs. "Right now, all are vendor sponsored, so you can see who's behind them. In the open source world, you also want to get people outside of the initial contributors. The real key will be Round 2 [of releases]."
Whether the industry gets behind an open source ESB shouldn't deflect attention from the bigger issues of an SOA infrastructure, said Jason Bloomberg, senior analyst at ZapThink LLC in Waltham, Mass. "The fact that there are now several open source ESB contenders, even before the market has settled on a common definition of ESB, is quite telling. The application server market took several years before open source products entered the fray -- and by that time, the definition of 'app server' had settled. In the ESB space, it seems that commoditization is setting in much earlier, indicating that ESB is truly a transitional market."
While ESB capability will be important, Bloomberg said, it is only a small part of an SOA. "The problem is that so much of distributed computing has been about the plumbing for so long that people are reluctant to shift the conversation to the really important questions behind SOA -- about architecture, process and governance."