Microservices, SOA, and EITA: Where To Draw the Line? Why to Draw the Line?

Surveying and drafting instruments and examples

In my part of the world, it’s not uncommon for people to say that someone wouldn’t recognize something if it “bit them in the [rude rump reference]”. For many organizations, that seems to be the explanation for the state of their enterprise IT architecture. For while we might claim to understand terms like “design”, “encapsulation”, and “separation of concerns”, the facts on the ground fail to show it. Just as software systems can degenerate into a “Big Ball of Mud”, so too can the systems of systems comprising our enterprise IT architectures. If we look at organizations as the systems they are, it should be obvious that this same entropy can infect the organization as well.

One symptom of this entropy is when the dividing lines blur, weakening or even removing constraints. While the term “constraint” commonly has a negative connotation, constraints provide the structure and definition of a system. Separation of concerns, encapsulation, and DRY are all constraints that are intended to provide benefit. We accept limits on concerns addressed, accessibility of internals and/or instances of code or data in order to reduce complexity, not just check off a philosophical box. If we remove or even just relax these types of constraints too much, we incur risk.

This blurring of lines can occur at any level and on multiple levels. Additionally, architectural weakness at a higher level of abstraction can negate strengths at lower levels. A collection of well-designed systems will not ensure a coherent enterprise IT architecture if there is overlap and redundancy without a clear understanding of which ones are authoritative. Accidental architecture is no more likely to work at higher levels of abstraction than lower ones.

Architectural design, at each level of granularity, should be intentional and appropriate to that level. The ideal, is not to over-regulate, but to strike a balance. Micromanaging internals wastes effort better spent on something beneficial; abdicating design responsibility practically guarantees chaos. An additional consideration is the fit between the human and technological aspects. Conway’s law is more than just an observation, it can be used as a tool to align applications to a specific business concern as well as aligning development teams to specific applications/application components.

Just as a carver takes note of the grain of the wood being shaped, so should an architect work with rather than against the grain of the organization.

Jessica Kerr’s post, “Microservices, Microbusinesses”, captures these concepts from the viewpoint of microservice architectures. Partitioning application concerns into microservices allows for internal flexibility at the cost of external conformance to necessary governance. As Kerr puts it, “…everybody is a responsible adult”:

That’s a lot of overhead and glue code. Every service has to do translation from input to its internal format, and then to whatever output format someone else requires. Error handling, caching or throttling, failover and load balancing and monitoring, contract testing, maintaining multiple interface versions, database interaction details. Most of the code is glue, layers of glue protecting a small core of business logic. These strong boundaries allow healthy relationships with other services, including new interactions that weren’t designed into the architecture from the beginning. For all this work, we get freedom on the inside.

Kerr also recognizes the applicability of this trade-off to the architecture of the organization:

Still, a team exists as a citizen inside a larger organization. There are interfaces to fulfill. Management really does need to know about progress. Outward collaboration is essential. We can do this the same way our code does: with glue. Glue made of people. One team member, taking the responsibility of translating cards on the wall into JIRA, can free the team to optimize communication while filling management’s strongest needs.

Management defines an API. Encapsulate the inner workings of the team, and expose an interface that makes sense outside. By all means, provide a reference implementation: “Other teams use Target Process to track work.” Have default recommendations: “We use Clojure here unless there’s some better solution. SQL Server is our first choice database for these reasons.” Give teams a strong process and technology stack to start from, and let them innovate from there.

“Good fences make good neighbors” not by keeping out, but by channeling traffic into commonly understood and commonly accepted directions. We recognize lines so as to influence those aspects we truly need to influence. More importantly, we recognize lines to prevent needless conflict and waste. The key is to draw the lines so that they work for us, not against us.


5 thoughts on “Microservices, SOA, and EITA: Where To Draw the Line? Why to Draw the Line?

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