With the increased adoption of SOA, companies are finding the ESB (enterprise service bus) the "must have" application to connect disparate systems. Although a number of open source ESBs, such as Mule, OpenESB, Apache ServiceMix, and JBoss ESB have been around for a while, these products take a relatively heavyweight approach to integration by implementing the JBI (Java Business Integration) specification. A more recent open source arrival, WSO2 ESB, takes a lightweight approach, focusing on integration based on Web service standards.

The Bottom Line WSO2 Enterprise Service Bus 1.0 WSO2, http://wso2.com Good  7.0 criteria score weight Interoperability 6 30% Features 6 20% Management 7 15% Scalability 9 15% Security 7 10% Value 9 10% Cost: Free; licensed under the Apache Software License; support available for between $2,000 and $8,000 per two-socket server Platforms: ESB: Windows XP/Vista (not fully tested on Windows Vista) or Linux. Administration console: Internet Explorer 6 or higher or Mozilla Firefox. Bottom Line: WSO2 ESB is a lightweight, fast, reliable, and easy-to-deploy ESB that supports many of the most important WS-* standards. Configuration is a bit more complicated than that of commercial ESBs, high availability options are limited, and only XML messaging are supported. But if you’re implementing a SOA around XML and Web services and are willing to consider open source, the WSO2 ESB should be on the short list. About our Reviews and Scoring Methodology

WSO2 ESB is based on the open source Web service mediation and routing engine, Apache Synapse, released in June 2007 after two years of development effort. Synapse was written with the goal of providing fast XML message processing.

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WSO2 provides several enhancements to the Synapse framework, and a few of the Synapse committers work for WSO2. Among the enhancements are a browser-based GUI for configuring the ESB; an integrated registry for browsing, loading, and configuring services; and graphical management and monitoring tools. All of these enhancements are released under the same open source software license, the Apache License, as Synapse itself. WSO2 also provides several intangible enhancements to Synapse, such as sponsoring an active user community, providing commercial support, and offering a Web site with tools and forums.

Of the WSO2 enhancements, the Web management console is one of the most useful. Although the underlying XML-based configuration files are not terribly difficult to understand, and clear examples are provided for most common EAI patterns, the console makes mistakes less likely. This is especially true in environments where the operators and administrators of the ESB are not developers, commonly the case in larger enterprises. Proxies, end points, and sequences can all be created and managed via the DHTML-based management console. Although configuring the ESB does require some knowledge of the underlying ESB principals, the task is significantly easier in this environment.

The WSO2 management console also provides useful monitoring functions, allowing administrators to see graphical depictions of message traffic to proxies, end points and sequences, as well as details such as min/max/average response times, faults, and total message counts.

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A simple registry
The WSO2 ESB includes a simple file-based registry that can be used to dynamically update the ESB by deploying new configuration files. The "integrated registry," as they call it, can be referred to by any particular instance of the ESB, so any number of ESB servers may be deployed with the same configuration. Local registry entries can override remotely derived values.

The simple registry works well enough, but making a remote file system available to all running instances of the ESB isn’t feasible in most production environments, where the ESB is likely to run in a clustered, high-availability configuration.

That said, one advantage to a file-based registry is ease of integration into an organization's existing change management practices. Most commercial vendors have their own form of version control for registries, and shoehorning these schemes into the IT organization's way of doing things is a constant source of frustration for the customer. WSO2 has a separate registry project that will ultimately provide a full feature set; hopefully it will also make it easy to adopt different change management practices.