Enterprise Service Bus

Rating:
Summary: Looks promising
Review: Chappell describes a highly promising but still speculative technology for connecting together enterprise-wide computations. It can also potentially be used to span different companies. Some of you may groan. Haven't we heard this already, several times? Remember the toutings of CORBA, Java's RMI, JMX, JMS, and the nascent Web Services?

Well, ESB draws upon often bitter lessons learnt with these earlier endeavours. CORBA was widely found to be too complex. RMI works only for tightly coupled systems, which do not scale well. So that became one reason for JMS, because it enabled loose coupling. But JMS is too low level. Web Services may indeed be promising, but face a danger of overspecifying a standard before enough practical experience is garnered.

ESB tries to subsume the best ideas from the above, and from other efforts. It promises loose coupling and an incremental rollout, amongst other things. The incremental ability may be key to getting a small scale project approved and implemented, due to its minimal investment.

You could think of ESB as taking the ideas of the JMX management console a step further. Plus, ESB can use JMX as a subsidiary technology.

Chappell also offers nice visual component schematics that could be used to represent and perhaps even assemble an ESB network. If this indeed is possible, it would be tremendous. Akin to the 1980s, when MicroSim offered a graphical version of Spice, with electronic parts availabled from a menu.

Rating:
Summary: Definitive study of emerging technology
Review: David Chappell's book on Enterprise Service Bus describes application integration technology using emerging open standards, event driven messaging and loosely coupled component architecture. The applications that dot any enterprise IT landscape are diverse and hence integrating them to cohesive, collaborating services is by no means simple. In its initial few chapters, Mr.Chappell does a brilliant job in describing typical enterprise IT systems, their current state of cohesiveness (or rather lack of it), importance of integration for business purpose and makes the case for a consistent pattern such as Enterprise Service Bus that can bring diverse IT systems together. He introduces the term "accidental architecture" to describe the ad-hoc, point-to-point integration between systems that had become many maintenance manager's nightmare and helped many to keep their jobs.

The very nature of application integration technology involves a host of technologies such as Message Oriented Middleware, XML processing such as JAXB, XPath or XSLT, protocols such as RMI, SOAP, HTTP. After the initial chapters the book transits to ESB in a rather abrupt manner without spending enough time to elaborate the core capabilities of the underlying technologies involved. The experienced readers may not find this limiting but a more systematic exposition to key technologies for ESB would have been helpful for many readers.

In the same vein, the author misses a substantial discourse on how the ESB container works. The description mainly focuses on "what" the container does rather than "how". For example, how the ESB container maintains transactional integrity across loosely coupled systems, how it copes up with erroneous messages or faulty services or how a repository of metadata can be useful to handle message versioning could have been described in a more in-depth manner.

The book provided numerous descriptions of complex integration scenarios. These examples elaborate the capabilities and scope of ESB approach and its benefit against "accidental architecture". However, focussing more on what this complex integration achieved rather than how ESB carried such tasks, and how were the key challenges solved, these descriptions often read like "mother-and-apple-pie" stories. They are all good, but aren't there any pain?

Besides its main limitation of lack of detailed mechanics, the book covers the breadth of the topics covering JMS, Web Services, new JBI standards, Portal Server, Application Server, Synchronous and asynchronous communication protocols, declarative rule based routing. All these concepts are important in ESB context and the author has tried to bring them together.

I hope experienced reader will be able to find a common thread between these concepts but am not so sure about those who are relatively new in the domain of system integration.



Rating:
Summary: Useful book but too Java Centric
Review: Perhaps a better title for the book would have been ESB for the J2EE technology stack. Although the author positions the book as a technology agnostic exploration of the technolgy, his lack of understanding of the Microsoft technology stack makes it impossible for him to pull this off. His obsession with JMS shows through in every chapter and the if he made a convincing argument about why JMS compatability is so useful in an ESB in a Microsoft based platform - I failed to spot it. Also his cavalier dismissal of Biztalk ( the latest version of which incidentally does have all the features of ESB he identifies ) is also quite surprising. As an architect who is working in a non java centric ,microsoft based environment, the book comes across as primarily written for people working on the Java stack. He does pay lip service to how the ESB in his view will work with any technology but the arguments fail to impress and appear incomplete. Given the fact that the essence of SOA and ESB in my view is interoperability, his espousal of JMS,a java specific mechanism, as a key standard ESBs must implement is strange to say the least.

Having said all that, I did think the book is extremely well written and the concepts outlines nicely complement Hohpe's book on intergation patterns in my view. He should perhaps have looked a bit more at that book to see how to truly write a technology independent book.


Rating:
Summary: A must-read for integration architects
Review: This book should be required reading for anyone involved with EAI, especially integration architects.

For those of you who may not have heard about ESB, it is a rather new approach to structuring a SOA (service-oriented architecture), using a distributed MOM infrastructure, XML messages, intelligent message routing, automatic transformation of messages, and centralized administration. The SOA approach to EAI solutions is compelling, but it is still too early in the game to tell if ESB will take the world by storm. It has a lot of promise, and many EAI vendors are jumping onto the bandwagon that Sonic, including Dave Chappell, helped to build.

The book offers the first comprehensive definition of an ESB that I have seen, almost entirely stripped bare of vendor-specific information and sales info. I say almost, for some issues (such as app-servers vs. ESB service containers) are presented in a less vendor neutral fashion than I would like. Overall, the book stays high on useful content, and low on vendor product positioning.

The books combines nicely described technical descriptions of ESB features with some high-level case studies culled from Dave's experiences in industry, or based on interviews with IT leaders that he conducted while researching the book.

The technical descriptions avoid becoming too detailed, but are sufficient to capture the essential issues encountered in integration. The book's diagrams, resembling Gregor-grams, are very useful, although I was a bit mystified to find a reference card for the glyphs used, tucked away in the back of the book. The diagrams are self-explanatory, IMHO.

The case studies are similarly abstract, avoiding introducing a level of detail that would cause the forest to be lost amongst the trees. At times I wished to a little more detail here, but I suspect I'm something of a glutton for punishment that way.

ESB is threatening to become something of a buzz word these days, what with IBM weighing into the ESB market. This book should help secure a rational, useful definition of Enterprise Service Bus before the marketing machines of the various integration vendors obliterate it in a storm of white papers and glossy brochures.

Rating:
Summary: Very good introduction to ESB
Review: Very good introduction to ESB