Spring Boot Actuator — Complete Notes

1. What is Spring Boot Actuator?

Spring Boot Actuator provides production-ready monitoring and management features for a Spring Boot application.

Application health monitoring
Metrics collection
Application info
Thread dumps
Environment properties
Loggers configuration
Beans inspection

2. Why Actuator is Important

Question	Actuator Endpoint
Is the application running?	/health
What beans are loaded?	/beans
What environment variables exist?	/env
What metrics are available?	/metrics
What threads are running?	/threaddump

3. Adding Actuator Dependency

Maven

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

Gradle

implementation 'org.springframework.boot:spring-boot-starter-actuator'

4. Default Endpoints

/actuator/health
/actuator/info

http://localhost:8080/actuator/health

{
 "status": "UP"
}

5. Exposing More Endpoints

management.endpoints.web.exposure.include=*

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

6. Important Actuator Endpoints

Endpoint	Description
/health	Application health status
/info	Application information
/metrics	Application metrics
/beans	Spring beans in application
/env	Environment properties
/loggers	Logger configuration
/threaddump	Thread dump
/heapdump	JVM heap dump
/mappings	All request mappings

7. Health Endpoint

/actuator/health

{
 "status": "UP",
 "components": {
   "db": { "status": "UP" },
   "diskSpace": { "status": "UP" }
 }
}

management.endpoint.health.show-details=always

8. Info Endpoint

info.app.name=Spring Boot Application
info.app.version=1.0
info.app.description=Learning Spring Boot Actuator

/actuator/info

9. Metrics Endpoint

/actuator/metrics

JVM memory usage
CPU usage
HTTP request count
Garbage collection

10. Beans Endpoint

/actuator/beans

11. Environment Endpoint

/actuator/env

12. Loggers Endpoint

/actuator/loggers

13. Actuator Architecture

Spring Boot Application
        |
   Actuator Module
        |
   Management Endpoints
        |
Health  Metrics  Info
        |
Monitoring Tools (Prometheus, Grafana)

14. Securing Actuator

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

15. Changing Base Path

management.endpoints.web.base-path=/manage

/manage/health
/manage/metrics

16. Different Management Port

management.server.port=9090

17. Real World Monitoring Stack

Spring Boot App
      |
Spring Boot Actuator
      |
Micrometer Metrics
      |
Prometheus
      |
Grafana Dashboard

18. Custom Actuator Endpoint (IMPORTANT)

Spring Boot allows developers to create custom actuator endpoints to expose custom application information.

Step 1: Create Custom Endpoint Class

import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
import org.springframework.stereotype.Component;

@Component
@Endpoint(id = "customInfo")
public class CustomActuatorEndpoint {

    @ReadOperation
    public String customData() {
        return "This is a custom actuator endpoint";
    }

}

Step 2: Enable Endpoint Exposure

management.endpoints.web.exposure.include=*

Step 3: Access Endpoint

http://localhost:8080/actuator/customInfo

Output

This is a custom actuator endpoint

19. Best Practices

Expose only necessary endpoints
Secure endpoints with Spring Security
Use metrics with monitoring tools
Use different management port in production
Avoid exposing sensitive data

20. Summary

Monitor application health
Track performance metrics
Inspect beans and environment
Create custom monitoring endpoints
Integrate with monitoring tools