What reasons are there against (or for) using the features of an Enterprise Service Bus when building an overall service adhering to a micro-service architecture (http://martinfowler.com/articles/microservices.html)? Why should we use dumb pipes and smart endpoints as opposed to using smarter pipes and be able to develop simpler services?
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4 Answers
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This is a huge question and probably can't be answered effectively in SO's Q&A format.
It depends what you are doing with it.
If you are building a single product which consists of lots of small pieces of function that can be thought of as being independent then microservices maybe the way to go.
If you are a large enterprise organisation where IT is not the main consideration of the board of directors as a competitive advantage and you work in a heavily regulate industry where new standards have to be applied across globally distributed projects with their own IT departments, some from new acquisitions, where you can't centrally control all the endpoints and applications within your organisation, then maybe you need an ESB.
I don't want to be accused of trying to list ALL the advantages of both approaches here as they wouldn't be complete and may be out of date quickly.
Having said that, in an effort to be useful to the OP:
If you look up how Spotify and Netflix do microservices you can find many things they like about the approach, including but not limited to: ease of blue/green deployment of individual services, decoupled team structures, and isolation of failures.
ESBs allow you to centrally administer and enforce policies, like legal requirements, audit everything in one place rather than hoping each team got the memo about logging everything, provide global statistics about load and uptime, as well as many other things. ESBs grew out of large enterprises where the driver was not customer response time on a website and speed of innovation (amongst other things) but Service Level Agreements, cost effectiveness and regulations (amongst other things).
There is a lot of value in both approaches. Microservices are being written about a lot at the moment, just as ESBs were 10-15 years ago. Maybe that's a progression, maybe it's just a change, maybe it's just that consumer product companies need to market themselves and large enterprises like to keep details private. We may find out in another 10 years. For now, it depends heavily on what you are doing. As with most things in programming, I'd start out simple and only move to the more complex solution if you need to.
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The term ESB has gotten overloaded, primarily in the Java world, to mean a big and complex piece of infrastructure that ends up hosting a bunch of poorly implemented logic in a central place.
Lighter-weight technologies like Apache Caml or NServiceBus don't encourage this kind of approach and indeed follow the "dumb pipes / smart endpoints" approach that has served as the backbone of the internet from the beginning.
NServiceBus specifically focuses on providing a higher level framework than most messaging libraries to make it easier to build smart endpoints that are more reliable through its deeper support for once-and-only-once message processing.
Full disclosure - I'm the founder of NServiceBus.
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Because services are isolated and pipes are reused.
Core idea of microservices is isolation - any part of the system can be replaced without affecting other services. Smart pipes means they have configuration, they have state, they have complex (which often means hard-to-predict) behavior. Thus, smart pipes are less likely to retain their exact behavior over time.
But - pipe change will affect every service attached while service change affects only other services that use it.
