Actuators, Metrics and Health

Estimated time to read: 2 minutes

Actuators¶

Spring Boot Actuator provides the following via various exposed HTTP or JMX endpoints:

• Health Checks
• Auditing
• Metrics Gathering
• HTTP tracing

Dependencies¶

To include Spring Boot Actuator in a project, the following dependencies are required:

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

Endpoints¶

spring-boot-starter-actuator provides a list of endpoints that assist with monitoring and managing the application. These endpoints can be found at localhost:8080/actuator.

• /actuator/health returns information about the applications health
• /actuator/info returns general information about the application obtained from build files
• /actuator/loggers returns application logs and the ability to update the log level at runtime
• /actuator/metrics returns metric information such as system information, JVM information, handlers, etc
• /actuator/mappings returns mapping information

Paths can also be followed to specific items which give more details around the required item. For example:

• /actuator/metrics/system.cpu.usage

Configuration¶

Endpoints can be configured within the application.properties file.

// ...

management.endpoints.web.exposure.include=info,health,metrics,loggers,beans,mappings
management.endpoint.health.show-details=always

// ...

Custom Endpoints¶

Spring Boot provides a selection of ready to use health indicators; however, custom indicators can be added as required.

For example, assuming that our API is reliant on another API on another system a custom indicator can be used and a custom endpoint generated.

To create a custom metric, a class can be created implementing the HealthIndicator interface and override the Health method.

// ...
@Component
public class ExternalAPIIndicator implements HealthIndicator {
    private final String message_key = "ExternalService";

    @Override
    public Health health() {
        if(!isRunningServiceExternalAPIService()) {
            return Health.down().withDetail(message_key, "Not Available").build();
        }
        return Health.up().withDetail(message_key, "Available").build();
    }

    private Boolean isRunningServiceExternalAPIService() {
        Boolean isRunning = false;
        // Add real logic here to test if the ExternalAPI Service is running
        return isRunning;
    }
}

//...