Spring Boot · Lesson 10 of 15

Actuator, Health and Metrics

Expose health, info and Prometheus metrics without leaking internals.

Intermediate
15 min read
3 objectives

Before this lessonLesson 9: Caching with Spring Cache

What you will learn

Add Actuator
Customise health
Scrape metrics

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Actuator exposes operational endpoints: health for the load balancer, metrics for Prometheus, info for the build version.

Dependencies and exposure

# application.yml
management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus
  endpoint:
    health:
      show-details: when_authorized
      probes:
        enabled: true          # /actuator/health/liveness and /readiness

A custom health indicator

@Component
public class DiskHealth implements HealthIndicator {
    @Override public Health health() {
        long free = new File("/").getUsableSpace();
        return free < 100_000_000
            ? Health.down().withDetail("free", free).build()
            : Health.up().build();
    }
}

Do not expose env or heapdump on the public internet. Put Actuator on a separate port or restrict it to the cluster network.

Up next · Lesson 11OpenAPI with springdocGenerate Swagger UI from your controllers and document security.