---
name: spring-boot-observability
description: Spring Boot 4 observability with Actuator, Micrometer, and OpenTelemetry. Use when configuring health indicators, health checks, custom metrics, distributed tracing, production endpoint exposure, Kubernetes probes, Cloud Run probes, logging, or monitoring. Covers Actuator endpoint security, Micrometer Timer/Counter/Gauge patterns, OpenTelemetry span customization, liveness/readiness probe setup, and metric tag best practices.
spring-boot-version: "4.0"
---

# 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 [references/TRACING.md](references/TRACING.md) for OpenTelemetry, span customization, context propagation

## Anti-Pattern Checklist

| Anti-Pattern | Fix |
|--------------|-----|
| DB checks in liveness probe | Move to readiness group only |
| 100% trace sampling in production | Use 10% or less |
| Exposing all endpoints publicly | Separate management port + auth |
| High-cardinality metric tags | Use low-cardinality tags only |
| Missing graceful shutdown | Add `server.shutdown=graceful` |
| No health probe groups | Separate liveness and readiness |

## Related Skills

| Need | Skill |
|------|-------|
| Dependency validation | `spring-boot-verify` |
| Actuator security | `spring-boot-security` |
| Actuator testing | `spring-boot-testing` |
| Module metrics | `spring-boot-modulith` |

## Critical Reminders

1. **Separate liveness from readiness** — Liveness: "is process alive?", Readiness: "can handle traffic?"
2. **Low cardinality tags only** — User IDs, request IDs = bad; status codes, regions = good
3. **Secure Actuator endpoints** — Use separate port or authentication
4. **Sample traces in production** — 100% sampling overwhelms collectors
5. **Graceful shutdown** — Allow in-flight requests to complete