When an application is deployed into production:

• We want to know immediately if some service goes down or is very slow
• We want to know immediately if any of the servers does not have sufficient free space or memory

This is called application monitoring.

Spring Boot Actuator provides a number of production-ready monitoring features.

We will add Spring Boot Actuator by adding a simple dependency:

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

As soon as the actuator is added to an application, it enables a number of endpoints. When we start the application, we see a number of added new mappings. The following screenshot shows an extract of these new mappings from the start up log:

The actuator exposes a number of endpoints. The actuator endpoint (http://localhost:8080/application) acts as a discovery for all other endpoints. The following screenshot shows the response when we execute the request from a Postman: