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Introduction

Spring Boot Actuator provides production-ready features to help you monitor and manage your application. It includes a number of built-in endpoints that allow you to interact with your application, gather metrics, understand traffic, and more.

Key Concepts

Endpoints: Actuator endpoints are HTTP endpoints that provide information about the application.
Metrics: Collect and expose metrics about the application.
Health Checks: Provide information about the health of the application.
Auditing: Track and log significant application events.

Setting Up Spring Boot Actuator

To get started with Spring Boot Actuator, you need to add the Actuator dependency to your pom.xml file:

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

Enabling Actuator Endpoints

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

management.endpoints.web.exposure.include=*

This configuration exposes all available endpoints. For a more secure setup, you can specify individual endpoints:

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

Common Actuator Endpoints

Here are some of the most commonly used Actuator endpoints:

Endpoint	Description
`/actuator`	Lists all available actuator endpoints.
`/actuator/health`	Provides health information about the application.
`/actuator/info`	Displays arbitrary application information.
`/actuator/metrics`	Shows metrics information.
`/actuator/env`	Exposes properties from the Spring Environment.
`/actuator/loggers`	Shows and modifies the logging levels of the application.

Practical Example

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

Step 1: Create a Spring Boot Application

Create a new Spring Boot project using Spring Initializr (https://start.spring.io/).
Add the following dependencies:
- Spring Web
- Spring Boot Actuator

Step 2: Configure Actuator

Add the following configuration to your application.properties file:

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

Step 3: Create a Controller

Create a simple REST controller to have some endpoints to monitor:

package com.example.demo;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello, World!";
    }
}

Step 4: Run the Application

Run your Spring Boot application and access the following Actuator endpoints:

Customizing Actuator Endpoints

You can customize the behavior of Actuator endpoints by adding custom health indicators, info contributors, and metrics.

Custom Health Indicator

Create a custom health indicator by implementing the HealthIndicator interface:

package com.example.demo;

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() {
        // Custom health check logic
        boolean isHealthy = checkHealth();
        if (isHealthy) {
            return Health.up().withDetail("Custom Health", "All systems go!").build();
        } else {
            return Health.down().withDetail("Custom Health", "Something went wrong!").build();
        }
    }

    private boolean checkHealth() {
        // Implement your custom health check logic here
        return true;
    }
}

Custom Info Contributor

Create a custom info contributor by implementing the InfoContributor interface:

package com.example.demo;

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

import java.util.Collections;

@Component
public class CustomInfoContributor implements InfoContributor {

    @Override
    public void contribute(Info.Builder builder) {
        builder.withDetail("customInfo", Collections.singletonMap("key", "value"));
    }
}

Practical Exercises

Exercise 1: Enable Additional Endpoints

Modify the application.properties file to expose the /actuator/env and /actuator/loggers endpoints.
Access these endpoints in your browser and observe the information provided.

Exercise 2: Create a Custom Metric

Create a custom metric using the MeterRegistry bean.
Expose this metric through the /actuator/metrics endpoint.

Solution for Exercise 1

management.endpoints.web.exposure.include=health,info,metrics,env,loggers

Solution for Exercise 2

package com.example.demo;

import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

@Component
public class CustomMetrics {

    @Autowired
    private MeterRegistry meterRegistry;

    @PostConstruct
    public void init() {
        meterRegistry.counter("custom.metric", "type", "example").increment();
    }
}

Conclusion

Spring Boot Actuator is a powerful tool for monitoring and managing your Spring Boot applications. By leveraging its built-in endpoints and customizing them as needed, you can gain valuable insights into the health, metrics, and overall performance of your application. In the next module, we will explore how to use Spring Boot Profiles to manage different configurations for different environments.

Spring Boot Actuator

Introduction

Key Concepts

Setting Up Spring Boot Actuator

Enabling Actuator Endpoints

Common Actuator Endpoints

Practical Example

Step 1: Create a Spring Boot Application

Step 2: Configure Actuator

Step 3: Create a Controller

Step 4: Run the Application

Customizing Actuator Endpoints

Custom Health Indicator

Custom Info Contributor

Practical Exercises

Exercise 1: Enable Additional Endpoints

Exercise 2: Create a Custom Metric

Solution for Exercise 1

Solution for Exercise 2

Conclusion

Spring Boot Course

Module 1: Introduction to Spring Boot

Module 2: Spring Boot Basics

Module 3: Building RESTful Web Services

Module 4: Data Access with Spring Boot

Module 5: Spring Boot Security

Module 6: Testing in Spring Boot

Module 7: Advanced Spring Boot Features

Module 8: Deploying Spring Boot Applications

Module 9: Performance and Monitoring

Module 10: Best Practices and Tips