cf-health-check-demo

Demo Showing how to Configure HTTP health checks on Cloud Foundr

Cloud Foundry can check application health using three methods process, port and http end point. These methods are documented at https://docs.cloudfoundry.org/devguide/deploy-apps/healthchecks.html

The http end point health check can be used with spring boot applications to point at the actuator health endpoint. CF will issue an HTTP GET on /actuator/health every 30 seconds if it gets and HTTP 200 response then it will consider the app healthy, if not it will restart the app.

When deploying the application you need to request the http health check via cf cli arguments or in the deployment manifest by adding the following.

  health-check-type: http
  health-check-http-endpoint: /actuator/health

This application contains a custom health indicator that can be toggled to observe how CF reacts to a failing health check.

@Component
public class ExampleHealthIndicator implements HealthIndicator
{
    private boolean state = true;

    @Override
    public Health health() {
        System.out.println("ExampleHealthIndicator called at " + LocalDateTime.now() + " state=" + state);
        if(state) {
            return Health.up().build();
        } else {
            return Health.down().build();
        }
    }

    public void setState(boolean state) {
        this.state = state;
    }

    public boolean getState() {
        return state;
    }
}

The app provides a set of end points to toggle the state of the health indicator as shown in the code below.

@RestController
public class RootController {

    @Autowired
    private ExampleHealthIndicator exampleHealthIndicator;

    @GetMapping
    public String get()
    {
        return "Health Checks Will Pass: "  + exampleHealthIndicator.getState();
    }

    @GetMapping("/fail")
    public String fail()
    {
        exampleHealthIndicator.setState(false);
        return "Health Checks Will Pass: "  + exampleHealthIndicator.getState();
    }

    @GetMapping("/pass")
    public String pass()
    {
        exampleHealthIndicator.setState(true);
        return "Health Checks Will Pass: "  + exampleHealthIndicator.getState();
    }
}

Run the application and check that it cf consider's it healthy. Then send get request to /fail to make the health indicator fail this will cause /actuator/health to start failing.

health check failures will be visible in the log stream from the application so make sure to monitor the app logs using the cf logs command to see the reports of health check failures.