Start Spring Boot refusing traffic at first

Right after all the beans are created and started, Spring Boot sets the LivenessState to CORRECT and ReadinessState to ACCEPTING_TRAFFIC.

However, after my application starts, it still needs to load a bunch of data on a ContextRefreshedEvent event listener.

How do I prevent setting the ReadinessState to ACCEPTING_TRAFFIC automatically?

You can create your own HealthIndicator that marks your app as ready after the data is loaded

@Component
public class DataLoadingHealthIndicator implements HealthIndicator {

    private boolean dataLoaded = false;

    @EventListener
    public void handleContextRefresh(ContextRefreshedEvent event) {
        // Load your data here
        dataLoaded = true;
    }

    @Override
    public Health health() {
        if (dataLoaded) {
            return Health.up().build();
        } else {
            return Health.down().build();
        }
    }
}

if you don't want to load the data in the health indicator, you can fire a custom event right after you load the data and listen to that event in your custom health indicator.

more useful info can be found here: java listen to ContextRefreshedEvent