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Is service-oriented architecture, or SOA, dead? You may be tempted to
think so. But that’s not really true. Yes, SOA itself may have receded
into the shadows as newer ideas have come forth, yet the remnants of SOA
are still providing the fuel that is propelling the microservices market
forward. That’s because incorporating SOA principles into the design and
build-out of microservices is the best way to ensure that your product
or service offering is well positioned for the long term. In this sense,
understanding SOA is crucial for succeeding in the microservices world.
In this article, I’ll explain which SOA principles you should adopt when
designing a microservices app.
In today’s mobile-first development environment, where code is king, it
is easier than ever to build a service that has a RESTful interface,
connect it to a datastore and call it a day. If you want to go the extra
mile, piece together a few public software services (free or paid), and
you can have yourself a proper continuous delivery pipeline. Welcome to
the modern Web and your fully buzzworthy-compliant application
development process. In many ways, microservices are a direct descendant
of SOA, and a bit like the punk rock of the services world. No strict
rules, just some basic principles that loosely keep everyone on the same
page. And just like punk rock, microservices initially embraced a
do-it-yourself ethic, but has been evolving and picking up some
structure which moved microservices into the mainstream. It’s not just
the dot com or Web companies that use microservices anymore—all
companies are interested.
For the purposes of this discussion, the following are the definitions I
will be using.
Microservices: The implementation of a specific business function,
delivered as a separate deployable artifact, using queuing or a RESTful
(JSON) interface, which can be written in any language, and that
leverages a continuous delivery pipeline.
SOA: Component-based architecture which has the goal of driving
reuse across the technology portfolio within an organization. These
components need to be loosely coupled, and can be services or libraries
which are centrally governed and require an organization to use a single
technology stack to maximize reusability.
As you can tell, microservices possess a couple of distinct features
that SOA lacked, and they are good:
Allowing smaller, self-sufficient teams to own a product/service
that supports a specific business function has drastically improved
business agility and IT responsiveness (to any directions that the
business units they support) want to take.
Automated builds and testing, while possible under SOA, are now
serious table stakes.
Allowing teams to use the tools they want, primarily around which
language and IDE to use.
Using-agile based development with direct access to the business.
Microservices and mobile development teams have successfully shown
businesses how technologists can adapt to and accept constant feedback.
Waterfall software delivery methods suffered from unnecessary overhead
and extended delivery dates as the business changed while the
development team was off creating products that often didn’t meet the
business’ needs by the time they were delivered. Even iterative
development methodologies like the Rational Unified Process (RUP) had
layers of abstraction between the business, product development, and the
developers doing the actual work.
A universal understanding of the minimum granularity of a service.
There are arguments around “Is adding a client a business function, or
is client management a business function?” So it isn’t perfect, but at
least both can be understood by the business side that actually runs the
business. You may not want to believe it, but technology is not the
entire business (for most of the world’s enterprises anyway). Back in
the days when SOA was the king on the hill, some services performed
nothing but a single database operation, and other services were adding
a client to the system, which led to nothing but confusion from business
when IT did not have a consistent answer.
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training After reading those definitions, you are probably
thinking, “Microservices sounds so much better.” You’re right. It is the
next evolution for a reason, except that it threw away a lot of the
lessons that were hard-learned in the SOA world. It gave up all the good
things SOA tried to accomplish because the IT vendors in the space
morphed everything to push more product. Enterprise integration patterns
(which define how new technologies or concepts are adopted by
enterprises) are a key place where microservices are leveraging the work
done by the SOA world. Everyone involved in the integration space can
benefit from these patterns, as they are concepts, and microservices are
a great technological way to implement them. Below, I’ve listed two
other areas where SOA principles are being applied inside the
microservices ecosystem to great success.
Microservices encourage point-to-point connections, and that each client
take care of their own translations for dates and other nuanced things.
This is just not sustainable as the number of microservices available
from most companies skyrockets. So in comes the concept of an Enterprise
Service Bus (ESB), which provides a means of communication between
different application in an SOA environment. SOA originally intended the
ESB to be used to carry things between service components—not to be
the hub and spoke of the entire enterprise, which is what vendors
pushed, and large companies bought into, and left such a bad taste in
people’s mouths. The successful products in the ESB have changed into
today’s API gateway vendors, which is a centralized way for a single
organization to manage endpoints they are presenting to the world, and
provide translation to older services (often SOA/SOAP) that haven’t been
touched in years but are vital to the business.
SOA had WS-* standards. They were heavy-handed, but guaranteed
interoperability (mostly). Having these standards in place, especially
the more common ones like WS-Security and WS-Federation, allowed
enterprises to call services used in their partner systems—in terms
that anyone could understand, though they were just a checklist.
Microservices have begun to formalize a set of standards and the vendors
that provide the services. The OAuth and OpenID authentication
frameworks are two great examples. As microservices mature, building
everything in-house is fun, fulfilling, and great for the ego, but
ultimately frustrating as it creates a lot of technical debt with code
that constantly needs to be massaged as new features are introduced. The
other side where standards are rapidly consolidating is API design and
descriptions. In the SOA world, there was one way. It was ugly and
barely readable by humans, but the Web service definition language
(WSDL), a standardized format for cataloguing network services, was
universal. As of April 2017, all major parties (including Google, IBM,
Microsoft, MuleSoft, and Salesforce.com) involved in providing tools to
build RESTful APIs are members of the OpenAPI Initiative. What was once
a fractured market with multiple standards (JSON API, WASL, RAML, and
Swagger) is now becoming a single way for everything to be described.
SOA originated as a set of concepts, which are the same core concepts as
microservices architecture. Where SOA fell down was driving too much
governance and not enough “Just get it done.” For microservices to
continue to survive, the teams leveraging them need to embrace their
ancestry, continue to steal the best of the ideas, and reintroduce them
using agile development methodologies—with a healthy dose of
anti-governance to stop SOA
from reappearing. And then, there’s the side job of keeping ITIL and
friends safely inside the operational teams where they thrive. Vince
Power is a Solution Architect who has a focus on cloud adoption and
technology implementations using open source-based technologies. He has
extensive experience with core computing and networking (IaaS), identity
and access management (IAM), application platforms (PaaS), and