Spring Boot Actuator: Crafting Custom Endpoints for Tailored Insights

Spring Boot Actuator provides a robust set of built-in endpoints for monitoring and managing your applications. However, there are scenarios where you might need to expose application-specific information or metrics beyond what the standard endpoints offer. This is where custom actuator endpoints shine, allowing you to tailor the information you expose to suit your application’s unique needs. Let’s delve into the process of creating and utilizing these custom endpoints.

1. Gradle/Maven Setup

To begin, ensure that your Spring Boot project includes the spring-boot-starter-actuator dependency. Here’s how to add it to your build.gradle (Gradle) or pom.xml (Maven) file:

Gradle:

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-actuator'
}

Maven:

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

2. Creating Custom Endpoints

Spring Boot Actuator provides annotations to easily create custom endpoints:

• @Endpoint: Marks a class as an actuator endpoint.
• @ReadOperation: Annotates a method to handle HTTP GET requests.
• @WriteOperation: Annotates a method to handle HTTP POST requests.
• @DeleteOperation: Annotates a method to handle HTTP DELETE requests.

Example: A Simple “Hello” Endpoint

import org.springframework.boot.actuate.endpoint.annotation.*;
import org.springframework.stereotype.Component;

@Component
@Endpoint(id = "hello")
public class HelloEndpoint {

    @ReadOperation
    public String hello() {
        return "Hello from a custom actuator endpoint!";
    }
}

This creates an endpoint accessible at http://localhost:8080/actuator/hello (assuming your application runs on port 8080) that returns the “Hello” message.

3. Advanced Endpoint Types

Actuator supports more complex endpoint interactions:

• Endpoints with Parameters:

@ReadOperation
public String greet(@Selector String name) {
    return "Hello, " + name + "!";
}

Access this with: http://localhost:8080/actuator/hello/greet?name=John

• Endpoints Returning JSON Data:

@ReadOperation
public Map<String, String> appInfo() {
    Map<String, String> info = new HashMap<>();
    info.put("appName", "My Spring Boot App");
    info.put("version", "1.0.0");
    return info;
}

• Endpoints Accepting Input (POST):

@WriteOperation
public String updateMessage(@RequestBody String newMessage) {
    // ... logic to update a message ...
    return "Message updated successfully";
}

4. Configuring application.yml

You can fine-tune the behavior of actuator endpoints using your application.yml or application.properties file. Here are some common configurations:

management:
  endpoints:
    web:
      exposure:
        include: "*"  # Expose all endpoints (use with caution in production)
        exclude: "env, beans"  # Exclude specific endpoints
  endpoint:
    hello:  # Configure your custom "hello" endpoint
      enabled: true
      cache:
        time-to-live: 10s  # Cache responses for 10 seconds

5. Important Considerations

• Endpoint Security: By default, all actuator endpoints are secured. Configure Spring Security to manage access to your custom endpoints.
• Endpoint IDs: Choose meaningful and unique IDs for your endpoints.
• Technology-Specific Endpoints: Consider using technologies like WebFlux or RSocket to create endpoints tailored to those communication styles.

Custom actuator endpoints offer a powerful way to extend the monitoring and management capabilities of your Spring Boot applications. By carefully crafting endpoints that expose application-specific information, you gain deeper insights into your application’s behavior and health, empowering you to build more robust and maintainable systems.