I'm going with Michael and Jason on this one. An ESB needs to be a _bus_ not a service development platform. As soon as an ESB becomes a SDP it ceases to be a bus and becomes just another application platform that you have to integrate with and which has application platform release schedules and complexities.
Keep the bus simple, keep it for mediation and don't put business logic into the bus. This was a rule that I started back in the EAI days where I'd see the EAI solution have business logic in it that should have been put into the various end points but wasn't due to "time" constraints, which normally meant they hit deadline 1 but missed 2-10 and then canned the programme. I think the issue here though is the "what is an ESB". With the BSB spec I tried to define what I meant by a business level service bus and it has many of the elements that you talk about Anne from a governance perspective. So maybe the challenge here isn't whether an ESB should be an SDP but the following 1) What are you SDPs 2) Keep the links between them simple and limited So some of the "richer" (i.e. basically non-standards based app server) ESBs fit into category 1 and some of the more "limited" (i.e. actually more powerful) ones fit into category 2. For me the purpose of a Bus is to enable producers and consumers to link, this means supporting the basic communication approaches (pub/sub included) and mediating between the different models (security and data). From an RM perspective I don't think it causes an issue as its effectively just part of the execution context (as long as you don't put any business logic and hence RWE into it). Keep the Bus (what ever you call it) stupid, because that stupidity gives you the ability to change the rest much more simply. Steve 2008/6/29 Anne Thomas Manes <[EMAIL PROTECTED]>: > Haven't we seen this flash before on this list? > > While I agree with Jason's overall perspective (i.e., don't let > technology drive your architecture and recognize that too much > reliance on an ESB can be harmful to your initiative), I disagree with > his recommendation to view an ESB primarily as a service intermediary. > An ESB is first an foremost a service platform -- one that includes > built-in transformation capabilities. > > As Jason says, > > "you need security, governance, quality, and management, in addition > to the transformation and content-based routing capabilities of Service > intermediaries, in order to build an effective SOA infrastructure." > > My overarching recommendation for service intermediaries is to keep > the number of intermediaries in the path to a minimum. Security, > governance, and management are required features in a SOA runtime > environment. These capabilities are supplied via SOA management or XML > gateways -- not by ESBs. And, oh by the way, SOA management and XML > gateway solutions can also support transformations and content-based > routing. Hence SOA management and XML gateways offer more > comprehensive intermediary solutions than ESBs -- at least for typical > intermediary requirements. > > In some circumstances, you may need more advanced routing and/or > transformation capabilities. i.e., you may need to support a pub/sub > model, reliable message delivery, or transformations based on a > database query or external algorithm. I view these scenarios as > "integration" rather than service-enablement, and as Jason indicated, > ESBs are good at integration. In these circumstances, it's appropriate > to use an ESB in the middle. > > But for more typical mediations (e.g., message validation, > transformations using XSLT, and simple routing) the management > infrastructure can handle it. Or--do the mediation at the endpoint. An > ESB is a useful component in a SOA infrastructure. It provides a > platform that enables a service to natively speak multiple protocols, > and it can transform messages to and from standard formats. > > My recommendation is to think of an ESB as an edge component -- not as > something that sits in the middle enabling universal communication. It > is one of many platforms that will host services within a SOA > environment. > > Anne > > On Sun, Jun 29, 2008 at 7:23 AM, Gervas Douglas > <[EMAIL PROTECTED]> wrote: >> >> >> Avoid Getting Lost on the (Enterprise Service) Bus >> >> Document ID: ZAPFLASH-2008530 | Document Type: ZapFlash >> By: Jason Bloomberg >> Posted: May. 30, 2008 >> >> So, you've been following ZapThink long enough to know that beginning a >> Service-Oriented Architecture (SOA) project by purchasing an Enterprise >> Service Bus (ESB) is starting at the wrong end of the initiative. >> Purchasing >> any technology, especially an ESB, at the beginning of an architecture >> project is a recipe for failure, you've been telling anyone who'll listen. >> But for whatever reason, your organization didn't pay attention to you, >> and >> now they've dropped a bundle on an ESB. Maybe your boss golfs with the >> vendor sales rep, or maybe the powers-that-be are listening to the wrong >> analyst firm, who knows. But in any case, you're stuck with that decision, >> and you're now expected to implement SOA with it. >> >> Fortunately, while purchasing an ESB too early in a SOA project does >> substantially increase your risk of failure, all is not lost. After all, >> you're not alone; this mistake is one of the most prevalent SOA snafus in >> IT >> shops around the world today, and not all of those projects end up as >> failures. Many of today's ESBs are now mature products, and can be an >> important part of a fully functional SOA implementation. Understanding the >> risks that buying an ESB too early in a SOA initiative presents, and >> dealing >> with those risks proactively, can turn a bad situation around and get your >> SOA initiative back on the right track. >> >> Understanding the Risks >> Fundamentally, the problem with buying the ESB first is that you might >> fall >> into the trap of doing things the way the ESB would like you to do them, >> in >> light of the fact that many ESBs are in many ways traditional middleware >> under the covers. After all, if middleware solved all your problems, then >> you wouldn't be considering SOA in the first place -- and adding Service >> capabilities to your middleware doesn't change this fundamental fact. >> >> In fact, the pitfalls that the ESB-first approach introduce fall into >> three >> broad categories: >> >> Taking an overly integration-centric perspective of the project -- Most >> ESBs >> are generally really good at connecting things -- in other words, most >> ESBs >> are quite capable integration middleware solutions. The problem is, SOA >> isn't about connecting things, it's about building loosely-coupled >> Services >> the business can leverage to meet changing process needs. We want to get >> away from the "connecting things" approach to distributed computing, and >> instead move to a "composing Services" paradigm, where integration becomes >> a >> byproduct of composition. >> >> The "middleware for your middleware" problem -- if it were practical (or >> even possible) to take a single piece of middleware and put it all by >> itself >> in the middle of your IT infrastructure, that would be one thing, but for >> most large (and many midsize) organizations, the vision of relying upon >> one >> piece of middleware to solve all integration problems is an unrealistic >> fantasy. In reality, organizations tend to have several different pieces >> of >> middleware, of different vintages and for different purposes. Introducing >> one or more ESBs into the mix means that now you have to integrate your >> ESBs >> with existing middleware as well as with each other, leading to the >> requirement of middleware for your middleware. Where will it ever end? >> >> The "good money after bad" fallacy -- The "good money after bad" fallacy >> is >> actually much broader than IT. People would rather throw money at an >> approach that's already cost a bundle than to switch approaches to a less >> expensive, but more effective alternative. If you've been buying >> middleware >> from a vendor for years, and now they tell you that you need an ESB, >> you're >> likely to take that advice, even if an alternative is lower cost and lower >> risk, simply because you've already spent so much with that vendor. >> >> ESB-First SOA Best Practices >> Now that you've steered your bus past the pitfalls, let's see if we can >> point it in the right direction moving forward. The most important thing >> to >> remember is that your architecture should drive the technology, not the >> other way around. Remember that ESBs, like any mature solution, come with >> a >> boatload of features -- many of which may not be appropriate for your >> situation. It is often figuring out which features not to use rather than >> the capabilities you should actually use that is the key to being >> successful >> with a product like an ESB. >> >> In particular, it is essential to take a process-driven approach to your >> infrastructure, instead of an integration-centric approach. Remember that >> building Service compositions that implement processes typically compose >> capabilities across multiple execution environments. Furthermore, those >> compositions are both dynamic and unpredictable -- the business process >> specialist in charge of the compositions may change them around long after >> you've deployed the Services. Governance becomes the key to managing that >> unpredictability, rather than pre-defined integrations. >> >> As a result, you shouldn't rely upon any one execution environment for >> your >> Service implementations, or any one process management environment either, >> for that matter. ESBs can offer an effective, managed execution >> environment >> for some of your Service interfaces, but you rarely if ever want to rely >> upon any one runtime environment for all of your Services. In other words, >> you should balance the advantages of running your Services "on the bus" >> with >> the fact that SOA allows you to leverage heterogeneity both on and off the >> bus. >> >> One essential point here is that SOA leverages interoperability more so >> than >> portability. In a virtual machine-based "write once, run anywhere" >> environment, whether Java or Microsoft Common Language Runtime >> (CLR)-based, >> distributed computing relies upon the portability of code. SOA, however, >> leverages the interoperability of the Service interfaces so that you don't >> need to move the underlying Service implementations around. As a result, >> running all your Services on the ESB can actually impede your SOA >> implementation, rather than support it. >> >> So, if you shouldn't think of your ESB as either integration middleware or >> as a universal Service execution environment, then what role should your >> ESB >> play? The answer is a Service intermediary. Transformations and >> content-based routing are the essential capabilities a Service >> intermediary >> should deliver, in conjunction with robust security and management. >> Building >> the Business Service abstraction depends upon transformations and >> content-based routing, and fortunately, most ESBs offer these >> capabilities. >> So, only use the traditional messaging middleware capabilities of your ESB >> if you really need them, and only leverage the Service runtime your ESB >> provides when convenient, but configure your ESB as an intermediary to get >> full value out of it as part of your SOA infrastructure. >> >> Not only does using an ESB as an intermediary enable you to architect the >> Business Service abstraction, it also resolves the "middleware for your >> middleware" problem, because intermediaries can intermediate between >> disparate integration technologies just as well as they can intermediate >> between Service providers and consumers. If you feel you need to use your >> ESB's message queuing technology, for example, just because it's there, >> however, then you won't get this benefit. >> >> The ZapThink Take >> Yes, you need security, governance, quality, and management, in addition >> to >> the transformation and content-based routing capabilities of Service >> intermediaries, in order to build an effective SOA infrastructure. But >> remember, ESBs aren't the be-all and end-all of SOA infrastructure -- many >> ESBs on the market include most of the above capabilities, but rarely if >> ever offer everything an organization requires. In fact, XML appliances >> are >> likely a better approach to security and policy enforcement, a >> registry/repository combined with a full-lifecycle SOA quality solution >> might serve as your design time and run time governance tools, while a >> robust SOA management solution might be a critical part of your >> infrastructure as well. In fact, many organizations leverage such products >> in conjunction with existing middleware to build out their SOA >> infrastructure without having to buy an ESB at all. >> >> The bottom line is to always remember that the business drives the >> architecture, and the architecture drives the technology. Don't let the >> technology drive the architecture! SOA is particularly adept at >> abstracting >> existing technology, which can include recently purchased products in >> addition to your legacy environment. But knowing which of your existing >> capabilities to leverage -- and which to forego -- can make or break your >> SOA initiative. >> >> >> Messages in this topic (1) Reply (via web post) | Start a new topic >> Messages | Members >> MARKETPLACE >> ________________________________ >
