System behaviour documentation
The Reaction Observer Library is one half of a larger effort to generate system-behaviour documentation automatically. This page gives just enough context to understand where the library fits.
The problem
The jEAP ArchRepo already documents runtime components (microservices) and their dependencies, including interface specifications. What it cannot see from static information alone is how a component reacts when it receives an event — the fine-grained, fast-changing functional behaviour of components and their interactions. Documenting this by hand tends to be incomplete or outdated. The Reaction Observer closes that gap by capturing the behaviour at runtime.
The two products
| Component | Role |
|---|---|
| jEAP Reaction Observer Library | Runs inside each microservice; observes reactions to consumed messages and publishes them as Kafka events (this repository) |
| jEAP Reaction Observer Service | A separate jEAP service that consumes those events, records and aggregates the reactions, and exposes them through a REST API |
The data flows: library (per service) → reaction events on Kafka → Reaction Observer Service → ArchRepo, which includes the observed reactions in the generated architecture documentation.
Preconditions
- An Application Platform runs at least one instance of
jeap-archrepo-service. - An instance of the jEAP Reaction Observer Service runs on that platform.
- Each microservice of the business application depends on this Reaction Observer Library (see Getting started).
What the library currently observes
The only reactions tracked today are domain events and commands produced through jEAP Messaging in response to a consumed message. Other kinds of reactions (for example outgoing HTTP calls) may be added in the future. For the recording details see How it works.