Spring Boot Actuator for Monitoring

Spring Boot Actuator is a powerful tool for monitoring and managing your Spring Boot application. It provides built-in endpoints to expose operational information about your application, such as health, metrics, environment details, and more. Below is a detailed guide on how to use Spring Boot Actuator for Monitoring.

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1. Add Spring Boot Actuator Dependency

To enable Actuator, add the following dependency to your pom.xml (for Maven) or build.gradle (for Gradle).

Maven:

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

Gradle:

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

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2. Actuator Endpoints

Actuator provides several built-in endpoints to monitor and interact with your application. By default, only the /actuator/health endpoint is enabled.

Common Endpoints:

• /actuator/health: Application health information.
• /actuator/info: Application information (customizable).
• /actuator/metrics: Application metrics (e.g., memory usage, HTTP requests).
• /actuator/env: Environment properties.
• /actuator/loggers: View and configure logging levels.
• /actuator/beans: List all Spring beans.
• /actuator/mappings: List all HTTP request mappings.
• /actuator/threaddump: Thread dump information.
• /actuator/httptrace: HTTP request traces.

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3. Enable and Expose Endpoints

By default, only the /actuator/health endpoint is exposed over HTTP. To expose other endpoints, configure the management.endpoints.web.exposure.include property in your application.properties or application.yml.

Example:

management:
  endpoints:
    web:
      exposure:
        include: "*"  # Expose all endpoints

You can also specify specific endpoints:

management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics

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4. Customizing Actuator Endpoints

a. Custom Health Indicators

You can create custom health indicators to check the status of specific components (e.g., database, external services).

import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;

@Component
public class CustomHealthIndicator implements HealthIndicator {

    @Override
    public Health health() {
        // Add custom logic to check health
        boolean isHealthy = checkServiceHealth();
        if (isHealthy) {
            return Health.up().build();
        } else {
            return Health.down().withDetail("Error", "Service is down").build();
        }
    }

    private boolean checkServiceHealth() {
        // Implement health check logic
        return true;
    }
}

b. Custom Info Endpoint

Add custom information to the /actuator/info endpoint.

info:
  app:
    name: My Spring Boot App
    version: 1.0.0
    description: A sample Spring Boot application

Or programmatically:

import org.springframework.boot.actuate.info.Info;
import org.springframework.boot.actuate.info.InfoContributor;
import org.springframework.stereotype.Component;

@Component
public class CustomInfoContributor implements InfoContributor {

    @Override
    public void contribute(Info.Builder builder) {
        builder.withDetail("customInfo", "This is custom info");
    }
}

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5. Securing Actuator Endpoints

Actuator endpoints can expose sensitive information, so it’s important to secure them.

a. Enable Security

Add Spring Security dependency:

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

b. Configure Security

Restrict access to Actuator endpoints:

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.web.SecurityFilterChain;

@Configuration
public class ActuatorSecurityConfig {

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/actuator/**").hasRole("ADMIN") // Only ADMIN can access Actuator
                .anyRequest().permitAll()
            )
            .httpBasic();
        return http.build();
    }
}

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6. Monitoring with Prometheus and Grafana

Spring Boot Actuator integrates with Prometheus and Grafana for advanced monitoring.

a. Add Micrometer Prometheus Dependency

<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-registry-prometheus</artifactId>
</dependency>

b. Expose Prometheus Metrics

The /actuator/prometheus endpoint will expose metrics in a format compatible with Prometheus.

c. Configure Prometheus and Grafana

• Set up Prometheus to scrape metrics from the /actuator/prometheus endpoint.
• Use Grafana to visualize the metrics.

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7. Custom Metrics

You can create custom metrics using Micrometer.

Example:

import io.micrometer.core.instrument.Counter;
import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.stereotype.Service;

@Service
public class MyService {

    private final Counter myCounter;

    public MyService(MeterRegistry registry) {
        myCounter = Counter.builder("my.custom.counter")
            .description("Counts custom events")
            .register(registry);
    }

    public void doSomething() {
        myCounter.increment();
    }
}

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8. Logging with Actuator

Use the /actuator/loggers endpoint to view and change logging levels dynamically.

Example:

• View current logging levels: GET /actuator/loggers
• Change logging level: POST /actuator/loggers/com.example

  {
    "configuredLevel": "DEBUG"
  }

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9. Best Practices

• Limit Exposure: Only expose necessary endpoints in production.
• Secure Endpoints: Use Spring Security to restrict access.
• Monitor Health: Regularly check the /actuator/health endpoint.
• Use Metrics: Integrate with Prometheus and Grafana for advanced monitoring.
• Customize Info: Add application-specific details to the /actuator/info endpoint.

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By leveraging Spring Boot Actuator, you can gain deep insights into your application’s performance, health, and operational metrics. Let me know if you need further assistance!