Chapter 3. Fundamentals of Event-Driven Microservices
An event-driven microservice is an application much like any other. It requires the exact same type of compute, storage, and network resources as any other application. It also requires a place to store the source code, tools to build and deploy the application, and monitoring and logging to ensure healthy operation. As an event-driven application, it reads events from a stream (or streams), does work based on those events, and then outputs results—in the form of new events, API calls, or other forms of work.
Chapter 1 briefly introduced the main benefits of event-driven microservices. In this chapter, I’ll cover the fundamentals of event-driven microservices, exploring their roles and responsibilities, along with the requirements, rules, and recommendations for building healthy applications.
The Basics of Event-Driven Microservices
Event-driven means that the events drive the business logic, just as water from a stream turns the water wheel of a mill (see Figure 3-1). Event-driven applications, be they micro or macro, typically do work only when there are events coming through it (or a timer expires—also an event). Otherwise, they sit idle until there are new events to process.
Figure 3-1. The water stream powers the wheel, as event streams power the microservice (Source: Laxey Wheel, wikimedia)
The consumer microservice ...
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