Actuator & Observability

Spring Boot Actuator exposes production-ready endpoints for monitoring, health checking, and managing a running Spring Boot application. It integrates natively with Prometheus, Grafana, and cloud health-check systems — essential infrastructure for any production deployment.

Key Points

• Include actuator: spring-boot-starter-actuator — endpoints at /actuator/* by default
• /actuator/health: UP/DOWN status — includes sub-indicators for DB, Redis, disk, and custom components
• /actuator/metrics: Micrometer metric names — /actuator/metrics/jvm.memory.used?tag=area:heap for specific metrics
• /actuator/info: application version, git commit, custom info — expose with management.info.git.mode=full
• /actuator/env: all configuration properties — sensitive values masked by default
• /actuator/loggers: view and change log levels at runtime without restart — POST {"configuredLevel": "DEBUG"}
• /actuator/threaddump and /actuator/heapdump: diagnostic dumps — use with JFR/async-profiler for production analysis
• Prometheus integration: add io.micrometer:micrometer-registry-prometheus → /actuator/prometheus exposes scrape endpoint
• Security: expose only health + info publicly; lock /actuator with Spring Security or move to management port

Spring Actuator: YAML config with Prometheus, custom HealthIndicator, Micrometer Counter + Timer, Kubernetes probe integration

# application.yml — actuator config
management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus,loggers
  endpoint:
    health:
      show-details: when-authorized   # only for authenticated users
      probes:
        enabled: true                 # /actuator/health/liveness + /health/readiness
  health:
    db:
      enabled: true
    redis:
      enabled: true
  metrics:
    tags:
      application: ${spring.application.name}   # add app label to all metrics
  info:
    git:
      mode: full

---
// Custom health indicator
@Component
public class ExternalApiHealthIndicator implements HealthIndicator {
    private final PaymentClient client;

    @Override
    public Health health() {
        try {
            client.ping();
            return Health.up().withDetail("payment-api", "reachable").build();
        } catch (Exception e) {
            return Health.down().withDetail("reason", e.getMessage()).build();
        }
    }
}

// Custom metric with Micrometer
@Service
public class OrderService {
    private final Counter ordersPlaced;
    private final Timer orderProcessingTime;

    public OrderService(MeterRegistry registry) {
        this.ordersPlaced = Counter.builder("orders.placed")
            .description("Total orders placed")
            .tag("channel", "web")
            .register(registry);
        this.orderProcessingTime = Timer.builder("orders.processing.time")
            .description("Order processing duration")
            .register(registry);
    }

    public Order place(OrderRequest req) {
        ordersPlaced.increment();
        return orderProcessingTime.record(() -> processOrder(req));
    }
}

// Kubernetes probes using actuator
# liveness: /actuator/health/liveness  → kills pod if DOWN
# readiness: /actuator/health/readiness → removes pod from load balancer