Observability: Spring Boot Actuator, Micrometer & Prometheus Metrics
Instrument production microservices with Spring Boot Actuator endpoints (`/actuator/health`, `/actuator/metrics`), Micrometer metrics collection, and Prometheus dashboard scraping.
The Three Pillars of Observability
### Observability Pillars in Java
- **Metrics (Micrometer + Prometheus)**: Numeric time-series counters, gauges, and timers tracking JVM heap, CPU, and HTTP request rates.
- **Logs (SLF4J + Logback + JSON)**: Structured application event logs.
- **Traces (OpenTelemetry + Zipkin/Jaeger)**: Distributed transaction correlation IDs tracking requests across microservices.