Spring Boot Actuator provides a set of tools for monitoring and managing Spring Boot applications. It includes several built-in endpoints that allow you to interact with your application and gather metrics, health information, and other useful data.

1. Endpoints: Actuator endpoints are HTTP endpoints that provide various information about the application.
2. Metrics: Metrics provide quantitative data about the application, such as memory usage, CPU usage, and request counts.
3. Health Checks: Health checks provide information about the health of the application and its components.
4. Custom Endpoints: You can create custom endpoints to expose additional information specific to your application.

To use Spring Boot Actuator, you need to add the spring-boot-starter-actuator dependency to your pom.xml file:

By default, only a few endpoints are enabled. You can enable additional endpoints by configuring your application.properties file:

This configuration exposes all available Actuator endpoints.

Here are some of the most commonly used Actuator endpoints:

Let's create a simple Spring Boot application and enable some Actuator endpoints.

Create a new Spring Boot application using Spring Initializr or your preferred method.

Add the following dependency to your pom.xml file:

In your application.properties file, add the following configuration to expose all Actuator endpoints:

Run your Spring Boot application. Once the application is running, you can access the Actuator endpoints. For example, you can access the health endpoint at http://localhost:8080/actuator/health.

To access metrics, navigate to http://localhost:8080/actuator/metrics. This endpoint provides various metrics about your application, such as memory usage, CPU usage, and request counts.

You can customize Actuator endpoints by creating custom health indicators, info contributors, and metrics.

Create a custom health indicator by implementing the HealthIndicator interface:

Create a custom info contributor by implementing the InfoContributor interface:

1. Create a new Spring Boot application and add the Actuator dependency.
2. Configure the application to expose all Actuator endpoints.
3. Create a custom metric that tracks the number of times a specific endpoint is accessed.
4. Access the custom metric via the /actuator/metrics endpoint.

1. Create a new Spring Boot application and add the Actuator dependency as shown above.

2. Configure the application to expose all Actuator endpoints in application.properties:

   management.endpoints.web.exposure.include=*
   

3. Create a custom metric by using the MeterRegistry:

   import io.micrometer.core.instrument.Counter;
   import io.micrometer.core.instrument.MeterRegistry;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.RestController;
   
   @RestController
   public class CustomMetricController {
   
       private final Counter customCounter;
   
       public CustomMetricController(MeterRegistry meterRegistry) {
           this.customCounter = meterRegistry.counter("custom.metric.counter");
       }
   
       @GetMapping("/custom-endpoint")
       public String customEndpoint() {
           customCounter.increment();
           return "Custom endpoint accessed!";
       }
   }
   

4. Run the application and access the custom endpoint at http://localhost:8080/custom-endpoint.

5. Access the custom metric via the /actuator/metrics/custom.metric.counter endpoint.

Spring Boot Actuator is a powerful tool for monitoring and managing Spring Boot applications. It provides a wide range of built-in endpoints for gathering metrics, health information, and other useful data. By customizing Actuator endpoints, you can tailor the monitoring capabilities to fit the specific needs of your application.