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.

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.

💡 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.

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.

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.

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.

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.

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.

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

What does Spring Boot Actuator provide?

  • Production-ready endpoints for monitoring and managing your app
  • A UI framework
  • A build tool
  • A database driver

Answer: Production-ready endpoints for monitoring and managing your app. Actuator exposes ready-made endpoints (health, metrics, info, and more) so you can monitor and manage a running application.

Which Actuator endpoint reports whether the app is up?

  • /actuator/shutdown
  • /actuator/health
  • /actuator/beans
  • /actuator/env

Answer: /actuator/health. The /actuator/health endpoint reports overall health (UP/DOWN) and aggregates component health indicators.

Which endpoint exposes application metrics?

  • /actuator/info
  • /actuator/threaddump
  • /actuator/metrics
  • /actuator/loggers

Answer: /actuator/metrics. /actuator/metrics lists metric names; /actuator/metrics/{name} shows a specific metric's measurements.

What is the /actuator/info endpoint for?

  • Listing all beans
  • Shutting down the app
  • Streaming logs
  • Showing arbitrary application info (build, git, custom details)

Answer: Showing arbitrary application info (build, git, custom details). /actuator/info surfaces general, customizable application information such as build and git details.

Which library backs Actuator's metrics collection?

  • Log4j
  • Micrometer
  • Jackson
  • Hibernate

Answer: Micrometer. Micrometer is the metrics facade Actuator uses; it can export to Prometheus, Datadog, and other monitoring systems.

By default in recent Spring Boot, which endpoint is exposed over HTTP?

  • All endpoints
  • None
  • Only health (and info)
  • Only shutdown

Answer: Only health (and info). For safety, only a minimal set (health, and info) is exposed over HTTP by default; others must be opted in.

How do you expose more endpoints over HTTP?

  • management.endpoints.web.exposure.include
  • server.expose=all
  • spring.actuator.on=true
  • endpoints.show()

Answer: management.endpoints.web.exposure.include. Set management.endpoints.web.exposure.include (e.g. health,info,metrics or *) in your configuration.

Why should you secure or limit Actuator endpoints in production?

  • They are slow
  • Some reveal sensitive internals (env, configprops, heapdump)
  • They use too much memory always
  • They break JSON

Answer: Some reveal sensitive internals (env, configprops, heapdump). Endpoints like env, configprops, and heapdump can leak sensitive data, so restrict exposure and protect them.

Micrometer acts as...

  • a database
  • a web server
  • a vendor-neutral facade so the same metrics export to many backends
  • a serializer

Answer: a vendor-neutral facade so the same metrics export to many backends. Like SLF4J for logging, Micrometer is a facade letting you instrument once and export to Prometheus, Datadog, etc.

A custom HealthIndicator lets you...

  • change the server port
  • rename endpoints
  • disable metrics
  • contribute a component's health (e.g. a downstream service) to /actuator/health

Answer: contribute a component's health (e.g. a downstream service) to /actuator/health. Implementing HealthIndicator adds your own UP/DOWN check that is aggregated into the overall health response.