Sunday, February 15, 2015

Microservices, Microbusinesses

To avoid duplication of effort, we can build software uniformly. Everything in one monolithic system or (if that gets unwieldy) in services that follow the same conventions, in the same language, developed with uniform processes, released at the same time, connecting to the same database.

That may avoid duplication, but it doesn't make great software. Excellence in architecture these days involves specialization -- not by task, but by purpose. Microservices divide a software system into fully independent pieces. Instead of limiting which pieces talk to which, they specify clear APIs and let both the interactions and the innards vary as needed.

A good agile team is like a microservice: centered around a common purpose. In each retro, the team looks for ways to optimize their workings, ways particular to that team's members, context, objectives.

When a service has a single purpose[1], it can focus on the problems important to that purpose. Authentication? availability is important, consistency, and security. Search? speed is crucial, repeatability is not. Each microservice can use the database suited to its priorities, and change it out when growth exceeds capacity. The business logic at the core of each service is optimized for efficient and clear execution.

Independence has a cost. Each service is a citizen in the ecosystem. That means accepting requests that come in, with backwards compatibility. It means sending requests and output in the format other services require, not overloading services it depends on, and handling failure of any downstream service. Basically, 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. We get the opportunity to exceed expectations, rather than straining standardized languages and tools to meet requirements.

Do the teams in your company have the opportunity to optimize in the same way?

I've worked multiple places where management decreed that all teams would track work in JIRA, with umpteen required fields, because they like how progress tracking rolls up. They can see high-level numbers or drill down into each team's work. This is great for legibility.[3] All the work fits into nice little boxes that add together. However, what suits the organizational hierarchy might not suit the work of an individual team.

Managers love to have a standard programming language, standard testing tools with reports that roll up, standard practices. This gives them the feeling that they can move people from team to team with less impact to performance. If that feeling is accurate, it's only because the level of performance is constrained everywhere.

Like software components, teams have their own problems to solve. Communication between individuals matters most, so optimize for that[2]. Given the freedom to vary practices and tools, a healthy agile team gets better and better. The outcome of a given day's work is not only a task completed: it includes ideas about how to do this better next time.

Tom Marsh says, "Make everyone in your organisation believe that they are working in a business unit about 10 people big." A team can learn from decisions and make better ones and spiral upward into exceptional performance (plus innovation), when internal consensus is enough to implement a change. Like a microbusiness.

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.

On a healthy team, people are accomplishing something together, and that's motivating. When we feel agency to share and try out ideas, when the external organization is only encouraging, then a team can gel, excel and innovate. This cohesive team culture (plus pairing) brings new members up to speed faster than any familiarity with tooling.

As in microservices, it takes work to fulfill external obligations and allow internal optimization. This duplication is not waste. Sometimes a little overhead unleashes all the potential.

[1] The "micro" in microservices is a misnomer: the only size restriction on a microservice is Conway's Law: each is maintained by a single team, 10 or fewer people. A team may maintain one or more system components, and one team takes full responsibility for the functioning of the piece of software.

[2] Teams work best when each member connects with each other member (NYTimes)

[3] Seeing Like a State points out how legibility benefits the people in charge, usually at the detriment of the people on the ground. Sacrificing local utility for upward legibility is ... well, it's efficiency over innovation.

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