“Microservices and API Complexity – Inside and Out” on Iasa Global

The signature benefit of a microservice architecture is that its highly granular nature allows for a great deal of flexibility in composing applications. Components are simplified by virtue of a high degree of focus. The ability to replace individual components is enhanced by the modularity inherent in the style.

A very significant drawback to microservice architecture is that its highly granular nature can lead to a great deal of complexity in composing applications. Highly focused components can force service consumers to become more involved in the internals of an interaction than they might otherwise wish. Unwanted options can become more of a source of confusion than useful modularity.

How do you resolve this paradox? See the full post on the Iasa Global Site

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“Microservice Mistakes – Complexity as a Service” on Iasa Global

I’m pleased to announce that I’ve been asked to continue as a contributor to the Iasa Global site. I’m planning to post original content there on at least a monthly basis. In the interim, please enjoy a re-post of “Microservice Mistakes – Complexity as a Service”

Form Follows Function on SPaMCast 339

This week’s episode of Tom Cagley’s Software Process and Measurement (SPaMCast) podcast features Tom’s essay on demonstrations and a Form Follows Function installment on microservices, SOA, and Enterprise IT Architecture.

For SPaMCast 339, Tom and I discuss my “Microservices, SOA, and EITA: Where To Draw the Line? Why to Draw the Line?” post.

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

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.

Microservice Mistakes – Complexity as a Service

Technical Empathy - the ability to see the system from the point of view of the caller of your code, not just the point of view of your code

—
Michael Feathers (@mfeathers) January 26, 2015

Michael Feathers’ tweet about technical empathy packs a lot of wisdom into 140 characters. Lack of technical empathy can lead to a system that is harder to both implement and maintain since no thought was given to simplifying things for the caller. Maintainability is one of those quality of service requirements that appears to be a purely technical consideration right up to the point that it begins significantly affecting development time. If this sounds suspiciously like technical debt to you, then move to the head of the class.

The issue of technical empathy is particularly on point given the popular interest in microservice architectures (MSAs). The granular nature of the MSA style brings many benefits, but also comes with the cost of increased complexity (among others). Michael Feathers referred to this in a post from last summer titled “Microservices Until Macro Complexity”:

It is going to be interesting to see how this approach scales. Some organizations have a relatively low number of microservices. Others are pushing higher, around the 600 mark. This is a bit beyond the point where people start seeking a bigger picture. If services are often bigger than classes in OO, then the next thing to look for is a level above microservices that provides a more abstract view of an architecture. People are struggling with that right now and it was foreseeable. Along with that concern, we have the general issue of dealing with asynchrony and communication patterns between services. I strongly believe that there is a law of conservation of complexity in software. When we break up big things into small pieces we invariably push the complexity to their interaction.

The last sentence bears repeating: “When we break up big things into small pieces we invariably push the complexity to their interaction”. Breaking a monolith into microservices simplifies each individual component, however, as Eran Hammer observed in “The Fallacy of Tiny Modules”, “…at some point, someone has to put it all together and then, all the complexity is going to surface…”. As Yamen Sader illustrated in his slide deck “Microservices 101 – The Big Why” (slide #26), the structure of the organization, domain, and system will diverge in an MSA. The implication of this is that for a given domain task, we need to know more about the details of that task (i.e. have less encapsulation of the internals) in a microservice environment.

The further removed the consumer of these services are from the providers, the harder and less convenient it will be to transfer that knowledge. To put this in perspective, consider two fast food restaurants: one operates in a traditional manner where money is exchanged for burgers, the other is a microservice style operation where you must obtain the beef, lettuce, pickles, onion, cheese, and buns separately, after which the cooking service combines them (provided the money is there also). The second operation will likely be in business for a much shorter period of time in spite of the incredible flexibility it offers. Additionally, it that flexibility only truly exists when the contracts between two or more providers are swappable. As Ben Morris noted in “Do Microservices create extra challenges for distributed development?”:

Each team will develop its own interpretation of the system and view of the data model. Any service collaboration will have to involve some element of translation or mapping and will be vulnerable to subtle bugs that can arise from semantic differences.

Adopting a canonical model across the platform can help to address this problem by asserting a common vocabulary. Each service is expected to exchange information based on a shared definition of the main entities. However, this requires a level of cross-team governance which is very much at odds with the decentralised nature of microservices.

None of this is meant to say that the microservice architecture style is “bad” or “wrong”. It is my opinion, however, that MSA is first and foremost an architectural style of building applications rather than systems of systems. This isn’t an absolute; I could see multiple MSA applications within an organization sharing component microservices. Where those microservices transcend the organizational boundary, however, making use of them becomes more complex. Actions at a higher level of granularity, such as placing an order for some product or service, involves coordinating multiple services in the MSA realm rather than consuming one “chunkier” service. While the principles behind microservice architectures are relevant at higher levels of abstraction, a mismatch in granularity between the concept and implementation can be very troublesome. Maintainability issues are both technical debt and a source of customer dissatisfaction. External customers are far easier to lose than internal ones.