THE ANATOMY OF A PRODUCTION HARNESS (COMPONENT MAP)

WHY A COMPONENT MAP HELPS Chapter 7 gave you seven layers, which are ways of grouping concerns. This chapter gives you something more concrete: a map of the actual parts, called components, that a production harness is built from. A component is a distinct piece of software with one clear job and a defined way of talking to the other pieces. Anatomy is the right word, because just as a doctor studies the heart, lungs, and stomach as separate organs that cooperate, an engineer studies a harness as separate components that cooperate. Production means a system that real users depend on, as opposed to a quick experiment on your own computer. A production harness needs more parts than an experiment, because real users expect it to be safe, affordable, and dependable. The component names in this chapter are common ones, but they are not universal. Different products may give the parts different names, combine two parts into one, or split one part into two. What matters is that you recognize the jobs that need doing, wherever the code happens to live. This book uses eight components: the instruction manager, the context builder, the model adapter, the tool registry, the permission resolver, the budget tracker, the logger, and the reporter. The first six do their work during the loop, and the last two record and summarize what happened.