spring-boot-observability

# Spring Boot Observability

Production observability with Actuator endpoints, Micrometer metrics, and OpenTelemetry tracing.

## Core Components

| Component | Purpose |
|-----------|---------|
| **Actuator** | Health checks, info, metrics exposure, operational endpoints |
| **Micrometer** | Metrics abstraction (Timer, Counter, Gauge, DistributionSummary) |
| **OpenTelemetry** | Distributed tracing (default in Spring Boot 4) |

## Core Workflow

1. **Add starters** → `actuator`, `micrometer-registry-*`, `opentelemetry`
2. **Configure endpoint exposure** → Secure sensitive endpoints
3. **Define health groups** → Separate liveness from readiness
4. **Add custom metrics** → Business-specific measurements
5. **Configure tracing** → Sampling, propagation, export

## Quick Patterns

See [EXAMPLES.md](EXAMPLES.md) for complete working examples including:
- **Production Actuator Configuration** with health groups and Kubernetes probes
- **Custom Health Indicator** with latency monitoring (Java + Kotlin)
- **Custom Micrometer Metrics** with Counter, Timer, and Gauge patterns
- **OpenTelemetry Span Customization** with Observation API
- **OpenTelemetry Configuration** for OTLP export
- **Actuator Endpoint Access Control** (Boot 4)

## Spring Boot 4 Specifics

- **OpenTelemetry** is the default tracer (replaces Brave)
- **Health Indicator** imports from `org.springframework.boot.health.contributor.*`
- **Endpoint Access Control** with `access: none/unrestricted/read-only`

## Detailed References

- **Examples**: See [EXAMPLES.md](EXAMPLES.md) for complete working code examples
- **Troubleshooting**: See [TROUBLESHOOTING.md](TROUBLESHOOTING.md) for common issues and Boot 4 migration
- **Actuator Endpoints**: See [references/ACTUATOR.md](references/ACTUATOR.md) for endpoint configuration, security, custom endpoints
- **Micrometer Metrics**: See [references/METRICS.md](references/METRICS.md) for Timer, Counter, Gauge, DistributionSummary patterns
- **Distributed Tracing**: See [