Health check called on the event loop

[cescoffier]

Describe the bug

With the following class:

@Readiness
@ApplicationScoped
public class DatabaseConnectionHealthCheck implements HealthCheck {

    @Inject
    FightService fightService;

    @Override
    public HealthCheckResponse call() {
        HealthCheckResponseBuilder responseBuilder = HealthCheckResponse.named("Database connection health check");

        System.out.println("Thread: " + Thread.currentThread().getName());
        try {
            List<Fight> fights = fightService.findAllFights();
            responseBuilder.withData("Number of rows in the database", fights.size()).up();
        } catch (IllegalStateException e) {
            e.printStackTrace();
            responseBuilder.down();
        }

        return responseBuilder.build();
    }
}

The call fails because it tries to access the database from an IO Thread.

Expected behavior
It should use a worker thread.

Actual behavior
It uses the event loop thread

[cescoffier]

The issue is that the route would also require the request scope.

[kenfinnigan]

Can we define specific routes to execute on the worker instead of IO thread?

I presume it's fine to have /health and /metrics served from a worker thread instead?