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Lab 2 - Introspection, Monitoring, and Metrics using Spring Boot Actuator

Set up the Actuator

  1. Continue with the project you completed in Lab 1.

  2. To pom.xml add the following dependency to include the starter for Spring Boot Actuator:

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

Introspection Endpoints

  1. Build the application:

    $ ./mvnw package

  2. Run the application:

    $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

  3. Try out the following endpoints. The output is omitted here because it can be quite large:

    http://localhost:8080/beans

    Dumps all of the beans in the Spring context.

    http://localhost:8080/autoconfig

    Dumps all of the auto-configuration performed as part of application bootstrapping.

    http://localhost:8080/configprops

    Displays a collated list of all @ConfigurationProperties.

    http://localhost:8080/env

    Dumps the application’s shell environment as well as all Java system properties.

    http://localhost:8080/mappings

    Dumps all URI request mappings and the controller methods to which they are mapped.

    http://localhost:8080/dump

    Performs a thread dump.

    http://localhost:8080/trace

    Displays trace information (by default the last few HTTP requests).

Build and Version Control Info

Spring Boot provides an endpoint (http://localhost:8080/info) that allows the exposure of arbitrary metadata.

One thing that it does well is expose information about the specific build and version control coordinates for a given deployment.

  1. Add the following plugin to your Maven build. It will add Git branch and commit coordinates to the /info endpoint:

    <plugin>
	<groupId>pl.project13.maven</groupId>
	<artifactId>git-commit-id-plugin</artifactId>
	<configuration>
		<dotGitDirectory>../../../.git</dotGitDirectory>
	</configuration>
</plugin>
    Note
    		 The path ../../../.git refers to the .git directory at the root of the course materials.

  2. Add the following properties to src/main/resources/application.yml:

    info:
  build:
    artifact: @project.artifactId@
    name: @project.name@
    description: @project.description@
    version: @project.version@

    These will add the project’s Maven coordinates to the /info endpoint. The Spring Boot Maven plugin will cause them to automatically be replaced in the assembled JAR.

  3. Build the application:

    $ ./mvnw package

  4. Run the application:

    $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

  5. Visit the application in the browser (http://localhost:8080/info), and verify that the output is similar to the following:

    {
   "git" : {
      "commit" : {
         "time" : "2015-12-06T17:25:32-0500",
         "id" : "78b0e1b"
      },
      "branch" : "master"
   },
   "build" : {
      "version" : "0.0.1-SNAPSHOT",
      "name" : "hello-spring-boot",
      "artifact" : "hello-spring-boot",
      "description" : "Demo project for Spring Boot"
   }
}

Health Indicators

Spring Boot provides an endpoint (http://localhost:8080/health) that allows for the notion of various health indicators.

  1. Normally, when Spring Security is not enabled, the /health endpoint will only expose an UP or DOWN value. To simplify working with the endpoint for this lab, we will turn off its sensitivity. Add the following to src/main/resources/application.yml:

    endpoints:
  health:
    sensitive: false

  2. Create the class io.pivotal.spring.FlappingHealthIndicator and into it paste the following code:

    @Component
public class FlappingHealthIndicator implements HealthIndicator{

    private Random random = new Random(System.currentTimeMillis());

    @Override
    public Health health() {
        int result = random.nextInt(100);
        if (result < 50) {
            return Health.down().withDetail("flapper", "failure").withDetail("random", result).build();
        } else {
            return Health.up().withDetail("flapper", "ok").withDetail("random", result).build();
        }
    }
}

    This demo health indicator will randomize the health check.

  3. Build the application:

    $ ./mvnw package

  4. Run the application:

    $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

  5. Visit the application in the browser (http://localhost:8080/health), and verify that the output is similar to the following (and changes randomly!):

    {
  status: "UP",
  flapping: {
    status: "UP",
    flapper: "ok",
    random: 69
  },
  diskSpace: {
    status: "UP",
    free: 113632186368,
    threshold: 10485760
  }
}

Metrics

Spring Boot provides an endpoint (http://localhost:8080/metrics) that exposes several automatically collected metrics for your application. It also allows for the creation of custom metrics.

  1. Create the class io.pivotal.spring.GreetingService and into it paste the following code:

    @Component
public class GreetingService {

    @Autowired
    CounterService counterService;

    @Value("${greeting}")
    String greeting;

    public String getGreeting() {
        counterService.increment("counter.services.greeting.invoked");
        return greeting;
    }
}

    This class is using the @Autowired CounterService to count the number of times that the getGreeting() method has been invoked.

  2. Refactor the contents of the class io.pivotal.spring.HelloSpringBootApplication:

    @Autowired
private GreetingService greetingService;

@RequestMapping("/")
public String hello() {
    return String.format("%s World!", greetingService.getGreeting());
}

public static void main(String[] args) {
    SpringApplication.run(HelloSpringBootApplication.class, args);
}

    hello() is now delegating the source of the greeting to our newly created GreetingService.

  3. Build the application:

    $ ./mvnw package

  4. Run the application:

    $ java -jar target/hello-spring-boot-0.0.1-SNAPSHOT.jar

  5. Visit the application in the browser (http://localhost:8080) and refresh the page several times.

  6. Now visit the /metrics endpoint (http://localhost:8080/metrics). Among the autogenerated metrics you should see a counter for the GreetingService invocations:

    counter.services.greeting.invoked: 16,