Spring Boot Actuator

Quick Start

<!-- pom.xml -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-registry-prometheus</artifactId>
</dependency>

# application.yml
management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus
  endpoint:
    health:
      show-details: when_authorized
  info:
    env:
      enabled: true

info:
  app:
    name: @project.name@
    version: @project.version@

---

Endpoints Configuration

management:
  endpoints:
    web:
      exposure:
        include: "*"  # Dev: all
        # include: health,info,metrics,prometheus  # Prod
        exclude: shutdown,threaddump
      base-path: /actuator

  endpoint:
    health:
      enabled: true
      show-details: when_authorized
      show-components: when_authorized
    shutdown:
      enabled: false  # Dangerous in prod

Available Endpoints

Endpoint	Description	Default
/health	Health status	Enabled
/info	App info	Enabled
/metrics	Metrics	Enabled
/prometheus	Prometheus format	Enabled*
/env	Environment properties	Disabled
/configprops	Configuration properties	Disabled
/beans	All beans	Disabled
/mappings	Request mappings	Disabled
/loggers	Logger levels	Disabled
/threaddump	Thread dump	Disabled
/shutdown	Graceful shutdown	Disabled

---

Health Indicators

management:
  health:
    db:
      enabled: true
    redis:
      enabled: true
    diskspace:
      enabled: true
      threshold: 10MB

Custom Health Indicator

@Component
public class ExternalServiceHealthIndicator implements HealthIndicator {

    private final RestClient restClient;

    @Override
    public Health health() {
        try {
            long startTime = System.currentTimeMillis();
            ResponseEntity<Void> response = restClient.get()
                .uri("/health")
                .retrieve()
                .toBodilessEntity();
            long responseTime = System.currentTimeMillis() - startTime;

            if (response.getStatusCode().is2xxSuccessful()) {
                return Health.up()
                    .withDetail("service", "external-api")
                    .withDetail("responseTime", responseTime + "ms")
                    .build();
            }
            return Health.down().build();
        } catch (Exception e) {
            return Health.down()
                .withDetail("error", e.getMessage())
                .build();
        }
    }
}

Full Reference: See health.md for composite indicators, health groups, and availability management.

---

Kubernetes Probes

management:
  endpoint:
    health:
      probes:
        enabled: true
      group:
        liveness:
          include: livenessState
        readiness:
          include: readinessState,db,redis

  health:
    livenessstate:
      enabled: true
    readinessstate:
      enabled: true

# Kubernetes deployment
spec:
  containers:
    - name: app
      livenessProbe:
        httpGet:
          path: /actuator/health/liveness
          port: 8080
        initialDelaySeconds: 30
        periodSeconds: 10

      readinessProbe:
        httpGet:
          path: /actuator/health/readiness
          port: 8080
        initialDelaySeconds: 10
        periodSeconds: 5

Full Reference: See health.md for availability state management and K8s probe configuration.

---

Metrics with Micrometer

management:
  metrics:
    enable:
      all: true
    tags:
      application: ${spring.application.name}
      environment: ${spring.profiles.active:default}
    distribution:
      percentiles-histogram:
        http.server.requests: true

Custom Metrics

@Service
public class OrderService {

    private final MeterRegistry meterRegistry;
    private final Counter orderCounter;
    private final Timer orderProcessingTimer;

    public OrderService(MeterRegistry meterRegistry) {
        this.meterRegistry = meterRegistry;
        this.orderCounter = Counter.builder("orders.created")
            .description("Total orders created")
            .register(meterRegistry);
        this.orderProcessingTimer = Timer.builder("orders.processing.time")
            .publishPercentiles(0.5, 0.95, 0.99)
            .register(meterRegistry);
    }

    public Order createOrder(OrderRequest request) {
        return orderProcessingTimer.record(() -> {
            Order order = processOrder(request);
            orderCounter.increment();
            return order;
        });
    }
}

Full Reference: See metrics.md for annotations, Prometheus config, and Grafana alerts.

---

Prometheus Integration

management:
  endpoints:
    web:
      exposure:
        include: prometheus
  prometheus:
    metrics:
      export:
        enabled: true

# prometheus.yml
scrape_configs:
  - job_name: 'spring-boot-app'
    metrics_path: '/actuator/prometheus'
    scrape_interval: 15s
    static_configs:
      - targets: ['localhost:8080']

---

Security

@Configuration
@EnableWebSecurity
public class ActuatorSecurityConfig {

    @Bean
    public SecurityFilterChain actuatorSecurityFilterChain(HttpSecurity http) throws Exception {
        return http
            .securityMatcher(EndpointRequest.toAnyEndpoint())
            .authorizeHttpRequests(auth -> auth
                .requestMatchers(EndpointRequest.to("health", "info")).permitAll()
                .requestMatchers(EndpointRequest.to("prometheus")).permitAll()
                .requestMatchers(EndpointRequest.to("env", "beans")).hasRole("ADMIN")
                .anyRequest().authenticated()
            )
            .httpBasic(Customizer.withDefaults())
            .build();
    }
}

# Separate management port
management:
  server:
    port: 9090
    address: 127.0.0.1

Full Reference: See custom-endpoints.md for custom endpoints and testing.

---

Best Practices

Do	Don't
Expose only necessary endpoints in prod	Expose all endpoints
Use health groups for K8s probes	Use single health endpoint
Configure metrics with consistent tags	Use high-cardinality tags
Implement custom health indicators	Rely only on built-in
Separate management port in production	Use same port as app

---

When NOT to Use This Skill

• Application profiling - Use spring-profiles for environment config
• Distributed tracing - Use micrometer-tracing for trace context
• Log aggregation - Use logging frameworks and ELK/Loki
• APM tools - Actuator complements Datadog, New Relic

---

Common Pitfalls

Error	Cause	Solution
Endpoints not exposed	Missing config	Add to management.endpoints.web.exposure.include
Health always UP	Indicators not configured	Verify dependencies in classpath
Metrics missing	Registry not configured	Add micrometer-registry-prometheus
Security bypass	Endpoints public	Configure security for actuator
Memory leak	High cardinality tags	Avoid userId, requestId as tags

---

Anti-Patterns

Anti-Pattern	Problem	Solution
Exposing all endpoints in prod	Security risk	Limit to health, metrics, prometheus
High cardinality metric tags	Memory explosion	Use bounded tag values
No auth on sensitive endpoints	Information leak	Configure Spring Security
Ignoring health groups	Poor K8s integration	Use liveness/readiness groups

---

Quick Troubleshooting

Problem	Diagnostic	Fix
Endpoints not exposed	Check config	Add to exposure.include
Health always DOWN	Check component	Fix failing indicator
Metrics missing	Check registry	Add Micrometer dependency
401 on endpoints	Security blocking	Configure actuator security
Prometheus not scraping	Check path	Verify /actuator/prometheus

---

Production Checklist

• Health endpoints configured
• K8s probes (liveness, readiness) active
• Prometheus scraping configured
• Alert rules defined
• Security on sensitive endpoints
• Custom health indicators for external deps
• Business metrics implemented
• Grafana dashboard configured

---

Reference Files

File	Content
health.md	Health Indicators, K8s Probes, Availability
metrics.md	Micrometer, Prometheus, Grafana Alerts
custom-endpoints.md	Custom Endpoints, Security, Testing

---

External Documentation

• Spring Boot Actuator
• Actuator Endpoints
• Micrometer