actor.cs

public abstract class AbstractActor<TMsg> : BackgroundService
{
    private readonly Channel<TMsg> _mailbox;

    public AbstractActor()
    {
        _mailbox = Channel.CreateUnbounded<TMsg>();
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (true)
        {
            //_mailbox.Reader.Count - можем записывать в метрику длину очереди
            var msg = await _mailbox.Reader.ReadAsync(stoppingToken);
            try
            {
                await HandleAsync(msg, stoppingToken);

                // можем инкрементить и считать rps обработки
            }
            catch (Exception e)
            {
                await HandleErrorAsync(e, msg, stoppingToken);
            }
        }
    }

    public async Task SendAsync(TMsg msg)
    {
        // тут запишем скорость вставки в очередь - будем видеть когда бомбят
        await _mailbox.Writer.WriteAsync(msg);
    }

    protected abstract Task HandleAsync(TMsg msg, CancellationToken ct);

    protected abstract Task HandleErrorAsync(Exception error, TMsg message, CancellationToken ct);
}



// можно поставить библиотеку union для автогенерации Match функции
[Union]
public abstract record SubscriptionManagerMsg
{
    public record Subscribe(string Ticker) : SubscriptionManagerMsg;

    public record Unsubscribe(string Ticker) : SubscriptionManagerMsg;
}

public interface ISubscriptionManager
{
    Task Subscribe(string ticker);

    Task Unsubscribe(string ticker);
}

// можно закрыть интерфейсом
public class SubscriptionManager : AbstractActor<SubscriptionManagerMsg>, ISubscriptionManager
{
    public SubscriptionManager()
    {
        // di работает
    }

    protected override async Task HandleAsync(SubscriptionManagerMsg msg, CancellationToken ct)
    {
        await msg.Match(
            sub => Console.WriteLine($"Subscribed to {sub.Ticker}"),
            unsub => Console.WriteLine($"Unsubscribed from {unsub.Ticker}"),
        );

        _pubsub.SendAsync(...);
    }

    protected override async Task HandleErrorAsync(
        Exception error,
        SubscriptionManagerMsg message,
        CancellationToken ct)
    {
        logger.LogError(error);
    }

    public async Task Subscribe(string ticker)
    {
        await SendAsync(new SubscriptionManagerMsg.Subscribe(ticker));
    }

    public async Task Unsubscribe(string ticker)
    {
        await SendAsync(new SubscriptionManagerMsg.Unsubscribe(ticker));
    }
}