Spring Boot Actuators Use Guide

09/09/202208/09/2022 Rodrigo Alonso Aviles

An Actuator is made of already-predefined functionalities used in production by our application. It allows you to monitor the application, collect metrics, understand the traffic or understand the state of your database in a trivial way.

The main benefit of this library is that you can get production-level tools without having to implement the features yourself.

An Actuator is mainly used to expose operational information about the application once it is running: status, metrics, information, dumping, environment, etc. For its use, it uses HTTP endpoints or JMX beans to allow interaction with the Actuator. In the case of this guide, it is implemented using HTTP endpoints.

Once the dependency is instated in the project, several endpoints are available for use. Next, we will explain how to implement it and use it in your projects.

How do I implement it?

First of all, you need to add the dependencies in your Spring Boot project:

<dependency> 
    <groupId>org.springframework.boot</groupId> 
    <artifactId>spring-boot-starter-actuator</artifactId> 
    <version>2.2.6.RELEASE</version> 
</dependency>

With this, you already have all the functionalities available at the moment you launch our application.

Once launched, all endpoints under the path «/{aplicación}/actuator» will be automatically generated.

Predefined Endpoint Extension

One of the features that Spring Boot Actuators offers is the possibility of extending the predefined endpoints that are already offered by the library itself.

To do this, you can follow this example in which the «/health» endpoint is extended:

@Component 
public class HealthCheck implements HealthIndicator { 

@Override 
    public Health health() { 

//Llamadas a diferentes métodos que nos devuelven el estado de nuestros servicios 
     Boolean genStatus=isRunningServiceGenerator(); 
     Boolean libStatus=isRunningServiceLibraries(); 
     Boolean modStatus=isRunningServiceModules(); 
 
     HashMap<String,String> details=new HashMap<String,String> (); 
     details.put("Libraries Service", libMsg); 
     details.put("Modules Service", modMsg); 
     details.put("Generator Service", genMsg); 

//En el caso de que alguno de nuestros servicios no esté en un estado correcto, se indicará que el servicio no está correcto 
        if (!genStatus || !libStatus || !modStatus)					 
               return Health.down().withDetails(details).build(); 

     return Health.up().withDetails(details).build(); 
    } 
}

Creating a new endpoint

Another of the possibilities offered to us with the Actuators is the creation of endpoints designed and personalized by the users.

To do this, you can follow this example:

@Component 
public class CustomEndpoint implements Endpoint<List<String>> { 
     
    @Override 
    public String getId() { 
       return "customEndpoint"; 
    } 
  
    @Override 
    public boolean isEnabled() { 
        return true; 
    } 
  
    @Override 
    public boolean isSensitive() { 
        return true; 
    } 
  
    @Override 
    public List<String> invoke() { 

        // Custom logic to build the output 
        List<String> messages = new ArrayList<String>(); 

        messages.add("This is message 1"); 
        messages.add("This is message 2"); 

        return messages; 

    } 

}

Configuration in Rancher

Since the Actuators provide with information about the status your applications are in, you can use it to manage the control over these.

Within Rancher, when deploying or updating our services, there is a tab called «Health Check», with which you can set application health checks so that, in case of many errors, it can be automatically restarted or marked to indicate to developers that it is not in optimal condition.

Using the endpoint generated by Spring Boot Actuators, you can set a policy like the following: