4.4 Spring Boot Actuator

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Spring Boot Actuator brings production-ready monitoring, telemetry, and management endpoints to your running application via HTTP or JMX.

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What is Spring Boot Actuator?

Actuator provides production-ready features for monitoring and managing Spring Boot applications.

Common endpoints include:

/actuator/health
/actuator/info
/actuator/metrics

Other endpoints exist, but they should be exposed carefully.

Example configuration:

management.endpoints.web.exposure.include=health,info,metrics

1. Key Actuator Endpoints

Endpoint	Purpose	Security Default
/actuator/health	Shows application uptime status (UP, DOWN, OUT_OF_SERVICE). Used by Kubernetes probes.	Exposed by default
/actuator/info	Arbitrary application metadata (git commit hash, version, build time).	Disabled by default
/actuator/metrics	JVM memory, thread pool usage, HTTP request latencies.	Disabled by default
/actuator/env	Inspects currently loaded environment properties.	Disabled by default (Sensitive)
/actuator/beans	Full catalog of all registered Spring beans in the container.	Disabled by default
/actuator/loggers	Query and dynamically adjust logging levels at runtime without restarting!	Disabled by default

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2. Exposing & Securing Actuator in application.yml

management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus
      base-path: /actuator
  endpoint:
    health:
      show-details: when-authorized
      probes:
        enabled: true # Enables /actuator/health/liveness and readiness for K8s
  server:
    port: 8081 # Separate management port from user-facing port 8080!

Security Warning: Exposing sensitive endpoints like /actuator/env or /actuator/heapdump publicly without authentication can leak database passwords and secrets. Always secure the management port or restrict it to internal VPC networks.

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3. Custom Health Indicators

You can write custom health indicators to check downstream dependencies:

@Component
public class PaymentGatewayHealthIndicator implements HealthIndicator {

    private final PaymentGatewayClient client;

    public PaymentGatewayHealthIndicator(PaymentGatewayClient client) {
        this.client = client;
    }

    @Override
    public Health health() {
        try {
            boolean isReachable = client.ping();
            if (isReachable) {
                return Health.up().withDetail("provider", "Stripe").withDetail("latencyMs", 12).build();
            }
            return Health.down().withDetail("error", "Ping timeout").build();
        } catch (Exception ex) {
            return Health.down(ex).build();
        }
    }
}