Among SOA technologies, the ESB is one of the most discussed options for open source. The ESB is a popular open source choice because the amount of flexibility and integration needed for implementation means that vendor lock-in with a commercial product can have a greater effect than with other technologies. "If you buy Oracle, you have to adapt your architecture to your middleware. If you go open source, you can adapt your middleware to your architecture," said Sanjiva Weerawarana, Founder and CEO of WSO2, in recent story on open source ESBs. Ross Mason, co-founder and CTO of MuleSource, echoed Weerawarana's sentiments: "With open source, it's tailored to real value. You can say, 'If I don't need complex event processing, don't send it to me."
ESBs, though, come with the same risks associated with most open source products. When SearchSOA.com contributor George Lawton spoke about open source ESBs with Gartner Research VP Jess Thompson in July, Thompson pointed out that open source ESBs often contain more bugs than commercial products because their providers cannot spend as much money on rigorous testing. Fixing those bugs costs money and manpower that can out-weigh other benefits. "If the operational expenses are high in terms of staffing," said Thompson, "The overall cost of ownership for open source can be higher than for licensed technology."
Despite these risks open source ESBs remain a viable choice, especially for those wary of vendor lock-in. "Avoiding lock-in was a major driver for Web services and SOA," wrote Jack Vaughan in a recent editorial on open source ESBs. "And it is the same these days with ESB-related development."
Open Source SOA Quick Guide
Part 1: Benefits of open source go beyond cost savings
Part 2: Open source ESBs drive integration but not without risk
Part 3: Application development frameworks offer open source alternatives
Part 4: Open source options exist for BPM, IDEs, and more
Open source ESB resources
Our new ESB tutorial provides the tips, expert advice, definitions, implementation examples, trends and news you need to get started with or optimize the performance of an enterprise service bus.
Open source ESB user story
Concur, a Redmond, Wash.-based provider of an on-demand employee expense reporting system for corporate customers, has deployed an open source ESB and servers with data services functionality to cut down the work required to meet end users' needs to obtain finance, accounting, and customer information.
CXF open source framework merges SOAP toolkit with Celtix ESB Celtix was a open source project to develop an enterprise service bus framework (ESB) to promote integration of Java components based on code donated by IONA and initially housed as part of ObjectWeb. Celtix merged with the XFire project to become Apache CXF.
MuleSoft is the creator of the Mule ESB. The Mule ESB is the most widely downloaded open source ESB.
The WSO2 ESB is designed to be extremely lightweight and scalable. It includes graphical editing of service interaction and XML support.
Apache ServiceMix ESB
The Apache Service Mix ESB is built on the Java Business Integration specification and includes support for Spring.