Functional programming is waiting for microservices

Functional programming has been bubbling on the edge of mainstream development for years (perhaps decades). The advent of microservices may give functional programming its big break.

Why has it taken so long for the industry to adopt functional programming? I can think of a few reasons:

• The effort to learn the techniques of functional programming
• The effort to convert existing programs
• The belief that current techniques are "good enough"

Individual developers (and teams of developers) have already learned the techniques of object-oriented programming. They are comfortable with them. They know the tools and understand the issues of object-oriented development. Changing to functional programming is a big change, with new techniques and new issues. That change can make people reluctant to switch to functional programming.

Existing systems are large and complex. Converting them to functional programming is a large effort, and one that must be done completely. The switch from procedural programming to object-oriented programming could be done gradually, especially if you were moving from C to C++. Functional programming has no gradual path.

Switching from object-oriented programming to functional programming incurs a cost, and the benefits are not so clear. The "return on investment" is not obvious.

These are all reasons to not switch from object-oriented programming to functional programming. (And they're pretty good reasons.)

Microservices change the equation.

Microservices are small, independent services. Changing an existing system (probably a large, monolithic system) to one that is composed of microservices is a large significant effort. It requires the decomposition of the monolith into smaller pieces.

If one is constructing small, independent services, either as part of a re-engineering effort or a new system, one can certainly consider functional programming -- if only for some of the microservices. Writing small functional programs is much easier than writing large systems in a functional language. (A statement that holds for object-oriented programming languages, and procedural languages, and assembly language.)

For microservices, a functional language may be better than an object-oriented one. Object-oriented languages are suited to large systems; classes and namespaces are designed for organizing the data and code of large systems. Microservices are, by design, small. It is possible that functional programming will be a better match for the small code of microservices.

If you are building microservices, or just contemplating microservices, think about functional programming.