Run some logic when the app health state change

Question

I have multiple health check in management.endpoint.health.group (foo, bar)

and I deploy my app within a kubernetes cluster,

What I want is when kube send me liveness request and the state of (foo, bar) is aggregated, at this moment (before replying) I want to run some logic based on this last state.

My Indicators are defined like this

@Component
public class FooHealthIndicator implements HealthIndicator {
  
  @Override
  public Health health() {

    Health.Builder builder = new Health.Builder();

    try {
      // some foo specific logic
      builder.up();

    } catch (Exception exception) {
      ...
      builder.down().withException(exception);
    }
    return builder.build();
  }

the same goes for BarHealthIndicator

Answer 1

What you have to do is implementing a component which extends HealthEndpointWebExtension and where you can intercept the group aggregated status :

public class HealthEndpointCustomExtension extends HealthEndpointWebExtension {

    private final Map<String,Status> lastStatusByGroup = new HashMap<>();

    public HealthEndpointCustomExtension(HealthContributorRegistry registry, HealthEndpointGroups groups, Duration slowIndicatorLoggingThreshold) {
        super(registry, groups, slowIndicatorLoggingThreshold);
    }

    @Override
    public WebEndpointResponse<HealthComponent> health(ApiVersion apiVersion, WebServerNamespace serverNamespace, SecurityContext securityContext, boolean showAll, String... path) {
        WebEndpointResponse<HealthComponent> response = super.health(apiVersion, serverNamespace, securityContext, showAll, path);

        if (path.length > 0) {
            String group = path[0];
            Status status = response.getBody().getStatus();
            Status lastStatus = lastStatusByGroup.put(group, status);

            if (lastStatus != null && !lastStatus.equals(status)) {
                //..do some logic
            }
        }

        return response;
    }

}

Then you just have to declare a bean factory method for this component inside a configuration class :

    @Bean
    HealthEndpointWebExtension healthEndpointWebExtension(HealthContributorRegistry healthContributorRegistry,
                                                          HealthEndpointGroups groups, HealthEndpointProperties properties) {
        return new HealthEndpointCustomExtension(healthContributorRegistry, groups,
                properties.getLogging().getSlowIndicatorThreshold());
    }