Optimizing app host start up time

[parched]

Our app host takes too long to start up (30+ seconds) which makes running tests using DistributedApplicationTestingBuilder very tedious.

The worse offender here is the service bus emulator, so if someone has some ideas how to speed that up, that would be great.

Currently, our aspnet API has a WaitFor on the service bus resource, but it doesn't really need to wait for it to start up, it just needs to wait for it to be ready to accept calls.

I would like the API to start running immediately, but not be marked as ready until the service bus resource is ready.
How can I do that?

[davidfowl]

I would like the API to start running immediately, but not be marked as ready until the service bus resource is ready.

The only way would be a health check. You can write a custom one or use WithHttpHealthCheck and add an endpoint that checks service bus' health. Are you trying to prevent the long wait chains but still block consumers until everything is ready?

[parched]

Are you trying to prevent the long wait chains but still block consumers until everything is ready?

Yes, exactly.

You can write a custom one or use WithHttpHealthCheck and add an endpoint that checks service bus' health.

Thanks, that works, I've written an extension method like this

    public static IResourceBuilder<T> WithHealthCheckDependency<T>(
        this IResourceBuilder<T> resource,
        IResourceBuilder<IResource> dependency
    )
        where T : IResource
    {
        return resource.WithHealthCheckDependency(dependency.Resource);
    }

    public static IResourceBuilder<T> WithHealthCheckDependency<T>(
        this IResourceBuilder<T> resource,
        IResource dependency
    )
        where T : IResource
    {
        var heathCheckName = $"{dependency.Name}_HealthCheckFor_{resource.Resource.Name}";
        var appBuilder = resource.ApplicationBuilder;

        bool dependencyIsReady = false;

        appBuilder.Eventing.Subscribe<ResourceReadyEvent>(
            dependency,
            (@event, cancellationToken) =>
            {
                dependencyIsReady = true;
                return Task.CompletedTask;
            }
        );

        appBuilder
            .Services.AddHealthChecks()
            .AddCheck(
                heathCheckName,
                () =>
                {
                    if (dependencyIsReady)
                    {
                        return HealthCheckResult.Healthy();
                    }
                    else
                    {
                        return HealthCheckResult.Unhealthy();
                    }
                }
            );

        return resource.WithHealthCheck(heathCheckName);
    }

However, I'm hitting this bug for one resource, it's working for service bus resource though.