How to inspect all events using the Async Daemon?

[AndrewInScotland]

I'm trying to implement a custom async projection that will allow me to inspect every event that's saved to Marten.
So I created events like the following, with each event implementing a common interface:

public interface IEventSourceEvent
{
}

public class CustomerCreated : IEventSourceEvent
{
    public Guid Id { get; set; }
    public string Name { get; set; }
}

public class CustomerEmailUpdated : IEventSourceEvent
{
    public string Email { get; set; }
}

This is my projection:

public class DemoInterfaceProjection : IProjection
{
    public Type[] Consumes => new Type[] { typeof(IEventSourceEvent) };

    public AsyncOptions AsyncOptions { get; } = new AsyncOptions();

    public void Apply(IDocumentSession session, EventPage page)
    {
        Console.WriteLine($"DemoInterfaceProjection: page.Sequences.Count: {page.Sequences.Count}. page.Events.Count: {page.Events.Count}");
        foreach (var @event in page.Events)
        {
            Console.WriteLine($"DemoInterfaceProjection: Processing event type {@event.Data.GetType().Name} with Id {@event.Id}");
        }
    }

    public Task ApplyAsync(IDocumentSession session, EventPage page, CancellationToken token)
    {
        this.Apply(session, page);
        
        return Task.CompletedTask;
    }

    public void EnsureStorageExists(ITenant tenant)
    {
    }
}

If I add this projection to my publishing app using .Events.InlineProjections.Add, the projection works as expected. I can see every event.

If I add this to my Async Daemon app using .Events.AsyncProjections.Add, the projection does not process the events.

However, if I change the projection to consume a concrete type:
public Type[] Consumes => new Type[] { typeof(CustomerCreated) };
Then the projection works, but I only see CustomerCreated events, which is not what I want - I want to see all of them.

Why does the async daemon consume concrete types, but not those derived from an interface?
Or is there a different way to do this?

[nikodemrafalski]

Hi, you have to pass concrete events types - the same that you register in your DocumentStore configuration,
I would suggest you just scan your assemblies for non abstract implementations of your marker interface and use it in Consumes property implementation.

For example, here's my configuration code section related to events, you can have similarly in your async projection.

_.Events.AddEventTypes(Assembly.GetTypes()
                    .Where(t => typeof(DomainEvent).IsAssignableFrom(t)));

[nikodemrafalski]

Additionally, as far as I remember, when you update Consumes collection and you want to make daemon start from scratch you must tell him that explicitly - to be honest I just mess with mt_event_progression table manually (reset seqId) and restart the daemon ;)