Asynchronous health checks

Defining asynchronous checks

SmallRye Health provides a way to define asynchronous checks that can be consumed in the reactive applications in a non-blocking manner. These checks are defined in a very similar way to the usual health checks only they implement a different interface:

@Liveness (1)
@ApplicationScoped (2)
public class LivenessAsync implements AsyncHealthCheck { (3)

    @Override
    public Uni<HealthCheckResponse> call() { (4)
        return Uni.createFrom().item(HealthCheckResponse.up("liveness-async"))
                .onItem().delayIt().by(Duration.ofMillis(10));
    }
}

1	The MicroProfile Health CDI qualifier is still required
2	The check still needs to be a CDI bean
3	The asynchronous checks must implement the `AsyncHealthCheck` interface
4	The return type of the health check `call()` method is `Uni<HealthCheckResponse>`

The Uni is one of the main types included in the Mutiny project on top of which asynchronous checks are built. Mutiny provides several ways to transform the most common reactive types to Uni, so if you are used to work with different reacitve library it should be an issue.

Consuming health checks asynchronously

The SmallRyeHealthReporter class was extended to provide variants of get health methods that end with *Async() (e.g. getLivenessAsync()) that return an Uni<SmallRyeHealth> so it can also be included in any reactive pipeline. Example uses of this API is demonstrated for instance in the AsyncHealthTest.

References