Spring Boot Actuator Skill

Overview

• Deliver production-ready observability for Spring Boot services using Actuator endpoints, probes, and Micrometer integration.
• Standardize health, metrics, and diagnostics configuration while delegating deep reference material to references/.
• Support platform requirements for secure operations, SLO reporting, and incident diagnostics.

When to Use

• Trigger: "enable actuator endpoints" – Bootstrap Actuator for a new or existing Spring Boot service.
• Trigger: "secure management port" – Apply Spring Security policies to protect management traffic.
• Trigger: "configure health probes" – Define readiness and liveness groups for orchestrators.
• Trigger: "export metrics to prometheus" – Wire Micrometer registries and tune metric exposure.
• Trigger: "debug actuator startup" – Inspect condition evaluations and startup metrics when endpoints are missing or slow.

Instructions

Follow these steps to configure Spring Boot Actuator for production-grade monitoring:

1. Add Actuator Dependency

Include spring-boot-starter-actuator in your build configuration (Maven or Gradle).

2. Expose Required Endpoints

Configure management.endpoints.web.exposure.include property with the specific endpoints you need. Avoid exposing sensitive endpoints like /env, /heapdump in production.

3. Secure Management Traffic

Apply Spring Security to management endpoints using @Configuration class with EndpointRequest matcher. Consider using a dedicated management port for additional isolation.

4. Configure Health Probes

Enable readiness and liveness probes with management.endpoint.health.probes.enabled=true. Create health groups to aggregate relevant indicators.

5. Set Up Metrics Export

Configure Micrometer registry for your monitoring system (Prometheus, OTLP, Wavefront). Add application tags for cross-service correlation.

6. Enable Diagnostic Endpoints

Turn on /actuator/startup, /actuator/conditions, and /actuator/httpexchanges for incident response troubleshooting.

7. Validate Configuration

Test each endpoint is accessible and returns expected data. Verify health checks integrate with your orchestrator (Kubernetes, Cloud Foundry).

Quick Start

1. Add the starter dependency.

   <!-- Maven -->
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-actuator</artifactId>
   </dependency>

   // Gradle
   dependencies {
       implementation "org.springframework.boot:spring-boot-starter-actuator"
   }

2. Restart the service and verify /actuator/health and /actuator/info respond with 200 OK.

Implementation Workflow

1. Expose the required endpoints

• Set management.endpoints.web.exposure.include to the precise list or "*" for internal deployments.
• Adjust management.endpoints.web.base-path (e.g., /management) when the default /actuator conflicts with routing.
• Review detailed endpoint semantics in references/endpoint-reference.md.

2. Secure management traffic

• Apply an isolated SecurityFilterChain using EndpointRequest.toAnyEndpoint() with role-based rules.
• Combine management.server.port with firewall controls or service mesh policies for operator-only access.
• Keep /actuator/health/** publicly accessible only when required; otherwise enforce authentication.

3. Configure health probes

• Enable management.endpoint.health.probes.enabled=true for /health/liveness and /health/readiness.
• Group indicators via management.endpoint.health.group.* to match platform expectations.
• Implement custom indicators by extending HealthIndicator or ReactiveHealthContributor; sample implementations live in references/examples.md#custom-health-indicator.

4. Publish metrics and traces

• Activate Micrometer exporters (Prometheus, OTLP, Wavefront, StatsD) via management.metrics.export.*.
• Apply MeterRegistryCustomizer beans to add application, environment, and business tags for observability correlation.
• Surface HTTP request metrics with server.observation.* configuration when using Spring Boot 3.2+.

5. Enable diagnostics tooling

• Turn on /actuator/startup (Spring Boot 3.5+) and /actuator/conditions during incident response to inspect auto-configuration decisions.
• Register an HttpExchangeRepository (e.g., InMemoryHttpExchangeRepository) before enabling /actuator/httpexchanges for request auditing.
• Consult references/official-actuator-docs.md for endpoint behaviors and limits.

Examples

Basic – Expose health and info safely

management:
  endpoints:
    web:
      exposure:
        include: "health,info"
  endpoint:
    health:
      show-details: never

Intermediate – Readiness group with custom indicator

@Component
public class PaymentsGatewayHealth implements HealthIndicator {

    private final PaymentsClient client;

    public PaymentsGatewayHealth(PaymentsClient client) {
        this.client = client;
    }

    @Override
    public Health health() {
        boolean reachable = client.ping();
        return reachable ? Health.up().withDetail("latencyMs", client.latency()).build()
                         : Health.down().withDetail("error", "Gateway timeout").build();
    }
}

management:
  endpoint:
    health:
      probes:
        enabled: true
      group:
        readiness:
          include: "readinessState,db,paymentsGateway"
          show-details: always

Advanced – Dedicated management port with Prometheus export

management:
  server:
    port: 9091
    ssl:
      enabled: true
  endpoints:
    web:
      exposure:
        include: "health,info,metrics,prometheus"
      base-path: "/management"
  metrics:
    export:
      prometheus:
        descriptions: true
        step: 30s
  endpoint:
    health:
      show-details: when-authorized
      roles: "ENDPOINT_ADMIN"

@Configuration
public class ActuatorSecurityConfig {

    @Bean
    SecurityFilterChain actuatorChain(HttpSecurity http) throws Exception {
        http.securityMatcher(EndpointRequest.toAnyEndpoint())
            .authorizeHttpRequests(c -> c
                .requestMatchers(EndpointRequest.to("health")).permitAll()
                .anyRequest().hasRole("ENDPOINT_ADMIN"))
            .httpBasic(Customizer.withDefaults());
        return http.build();
    }
}

More end-to-end samples are available in references/examples.md.

Best Practices

• Keep SKILL.md concise and rely on references/ for verbose documentation to conserve context.
• Apply the principle of least privilege: expose only required endpoints and restrict sensitive ones.
• Use immutable configuration via profile-specific YAML to align environments.
• Monitor actuator traffic separately to detect scraping abuse or brute-force attempts.
• Automate regression checks by scripting curl probes in CI/CD pipelines.

Constraints and Warnings

• Avoid exposing /actuator/env, /actuator/configprops, /actuator/logfile, and /actuator/heapdump on public networks.
• Do not ship custom health indicators that block event loop threads or exceed 250 ms unless absolutely necessary.
• Ensure Actuator metrics exporters run on supported Micrometer registries; unsupported exporters require custom registry beans.
• Maintain compatibility with Spring Boot 3.5.x conventions; older versions may lack probes and observation features.
• Never expose actuator endpoints without authentication in production environments.
• Health indicators should not perform expensive operations that could impact application performance.
• Be cautious with /actuator/beans and /actuator/mappings as they reveal internal application structure.

Reference Materials

• Endpoint quick reference
• Implementation examples
• Official documentation extract
• Auditing with Actuator
• Cloud Foundry integration
• Enabling Actuator features
• HTTP exchange recording
• JMX exposure
• Monitoring and metrics
• Logging configuration
• Metrics exporters
• Observability with Micrometer
• Process and Monitoring
• Tracing
• Scripts directory (scripts/) reserved for future automation; no runtime dependencies today.

Validation Checklist

• Confirm mvn spring-boot:run or ./gradlew bootRun exposes expected endpoints under /actuator (or custom base path).
• Verify /actuator/health/readiness returns UP with all mandatory components before promoting to production.
• Scrape /actuator/metrics or /actuator/prometheus to ensure required meters (http.server.requests, jvm.memory.used) are present.
• Run security scans to validate only intended ports and endpoints are reachable from outside the trusted network.