Monitoring with Actuator

Spring Boot Actuator bolts production-ready endpoints onto your app — /actuator/health , /actuator/metrics , /actuator/info — with Micrometer collecting metrics you can export anywhere.

Learn Monitoring with Actuator in our free Java course — a beginner-friendly interactive lesson with worked examples, a practice exercise and a quick reference.

Part of the free Java course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

Before You Start

You should be comfortable building a Spring Boot app and tweaking its configuration and profiles . Knowing a little about HTTP endpoints and JSON helps when reading the responses.

What You'll Learn

The Big Idea — The Dashboard of Your Application

💡 Analogy: Actuator is the dashboard and warning lights of your application, like a car's instrument cluster. /actuator/health is the big green "all systems go" light — and if the oil, brakes, or engine (any component) fails, it flips to red. /actuator/metrics is the set of gauges: speed, RPM, fuel — live numbers about how hard the engine is working. /actuator/info is the little plate showing the model and build. And just as you don't let strangers pop the hood and read the diagnostics port, you lock down the sensitive endpoints in production.

You don't build the dashboard yourself — Actuator wires it in; you just choose which gauges to show and to whom.

1️⃣ /health — Aggregated Status

The health endpoint combines many component checks into one status: if any indicator is DOWN, the whole app reports DOWN. The plain-Java model below shows that aggregation rule.

2️⃣ /metrics — Counters and Gauges

Metrics are collected by Micrometer . The core meter types are counters (ever-increasing totals, like request counts) and gauges (live values, like active sessions). The demo builds tiny versions to show what a registry holds.

3️⃣ Exposing Endpoints

By default only health (and info ) are exposed over HTTP. You opt into more with management.endpoints.web.exposure.include and can enrich /info with build metadata.

4️⃣ Adding a Custom HealthIndicator

Implement HealthIndicator to fold your own check (a downstream service, a queue, a license) into /actuator/health — the same aggregation you saw in section 1.

🧠 Quick Recall

Answer: DOWN — the overall status aggregates components and fails if any one fails.

Answer: Micrometer — a vendor-neutral facade that exports to many monitoring backends.

Answer: add it to management.endpoints.web.exposure.include (it isn't exposed by default).

🎯 YOUR TURN — Health Aggregation

Write overall(components) returning "UP" only when every component is up.

🧩 MINI-CHALLENGE — A Tiny Metrics Registry

Build a named-counter registry like Micrometer: increment by name, then print all metrics sorted.

Common Errors

• ❌ Expecting all endpoints by default. Only health/info are exposed over HTTP. Fix: add others to exposure.include .
• ❌ Exposing everything with * in production. Leaks sensitive data. Fix: expose only what you need and secure it.
• ❌ Showing full health details publicly. Reveals internals. Fix: show-details=when-authorized .
• ❌ Forgetting the starter dependency. No endpoints appear. Fix: add spring-boot-starter-actuator .
• ❌ Confusing counters and gauges. Counters only increase. Fix: use a gauge for values that go up and down.
• ❌ Leaving heapdump/threaddump open. DoS and disclosure risk. Fix: restrict to an internal management port.

Pro Tips

• 💡 Use /actuator/health for liveness/readiness probes in Kubernetes and load balancers.
• 💡 Export metrics to Prometheus by adding the Micrometer Prometheus registry — no code changes needed.
• 💡 Run Actuator on a separate management port ( management.server.port ) to isolate it from public traffic.
• 💡 Add custom HealthIndicator s for critical downstreams so a failure surfaces immediately.

📋 Quick Reference

Concept

Syntax / idea

Note

starter

spring-boot-starter-actuator

Adds endpoints

health

/actuator/health

UP/DOWN aggregate

metrics

/actuator/metrics

Browse meters

info

/actuator/info

App/build details

metrics lib

Micrometer

Facade to backends

counter

monotonic total

Only increases

gauge

current value

Up and down

expose

exposure.include=health,info,metrics

Opt in

custom check

implements HealthIndicator

Adds a component

secure

limit + protect endpoints

Production safety

📚 Resources / Keep Learning

• 📘 Actuator — Spring Boot reference
• 📗 Micrometer documentation
• 📗 Building a RESTful Web Service with Actuator — Spring guide

❓ Frequently Asked Questions

🎉 Lesson Complete!

You now know what Actuator adds, how /health aggregates component checks, how Micrometer collects counters and gauges behind /metrics , how to expose endpoints with exposure.include , and why sensitive endpoints must be secured in production.

Next up: Caching with @Cacheable — speeding up your app by remembering expensive results.

Practice quiz

Continue this course

• Previous: Testing the Data Layer
• Next: Caching with @Cacheable

Related lessons

• configuration and profiles