David Pallmann of Neudesic responded to my comment that "Physically distributed but logically centralized" didn't make any sense to me at all:
What exactly does this mean? To some this may sound like a contradiction. This simply means that a bus is physically more like the point-to-point architecture (spread out, no hub) but functionally more like the hub-and-spoke architecture (pub-sub messaging, centralized configuration and activity tracking, easy change management).
What exactly does this mean? To some this may sound like a contradiction.
This simply means that a bus is physically more like the point-to-point architecture (spread out, no hub) but functionally more like the hub-and-spoke architecture (pub-sub messaging, centralized configuration and activity tracking, easy change management).
Unfortunately, I wasn't confused about the seeming contradictory nature of these concepts. In other words, I understand the "what" and "how" of David's physically distributed/logically centralized approach.
I don't understand the "why". As in, "why would you want to do this?" or "why do you think this would work at any significant scale?".
If we check out Neudesic's page on their ESB product (which David pointed me to) we find the following blurb:
Centralized ManagementThe distributed nature of service oriented programming can create a management nightmare. Neuron·ESB supports this distributed architecture while simultaneously centralizing monitoring and configuration.
SOA's "distributed nature" is it's primary strength. SOA's not primarily about standards or ease-of-connectivity - though those obviously play a role. It's about enabling decentralized decision making. Since you can't be both centralized and decentralized, enforcing centralized management basically negates SOA's primary strength. This seems like the worst of both worlds to me. All the hassle of distributed decision making combined with all the hassle of centralized management.
Yes, decentralized decision making can create a management nightmare. Personally, a management nightmare is much more attractive anything centralized approaches have ever delivered in the IT industry.
Dare Obasanjo recently wrote "If You Fight the Web, You Will Lose". He was talking about the Web as a Platform, but it's good general advice. Can you imagine applying the marketing blurb above to the Internet at large?
Centralized ManagementThe distributed nature of service oriented programming the Internet can create a management nightmare. Neuron·ESB supports this distributed architecture while simultaneously centralizing monitoring and configuration.
If the Internet can somehow get by without centralized management, why can't you?