Multi-Instance Senkron

public sealed class EventBusRemoteTagBroadcaster : IRemoteTagBroadcaster
{
    // Process yaşam süresi boyunca sabit, process başına unique node kimliği.
    public static readonly string NodeId = Guid.NewGuid().ToString("N");

    private readonly IServiceScopeFactory _scopeFactory;
    private readonly ILogger<EventBusRemoteTagBroadcaster> _logger;

    public async ValueTask BroadcastInvalidationAsync(
        IReadOnlyCollection<string> tags, CancellationToken cancellationToken = default)
    {
        if (tags is null || tags.Count == 0) return;

        // Singleton broadcaster, Scoped IEventBus → per-call scope.
        using var scope = _scopeFactory.CreateScope();
        var eventBus = scope.ServiceProvider.GetRequiredService<IEventBus>();

        var evt = new CacheInvalidationIntegrationEvent(tags, NodeId);
        await eventBus.PublishAsync(evt, cancellationToken);
    }
}

[MessageUrn("urn:event:cache-invalidation:v1")]
public sealed class CacheInvalidationIntegrationEvent : IntegrationEvent
{
    public IReadOnlyCollection<string> Tags { get; init; } = Array.Empty<string>();

    // Hangi node yayınladı — receiver kendi event'ini atlamak için karşılaştırır.
    public string SourceNodeId { get; init; } = string.Empty;

    public CacheInvalidationIntegrationEvent() { }
    public CacheInvalidationIntegrationEvent(IReadOnlyCollection<string> tags, string sourceNodeId)
    {
        Tags = tags;
        SourceNodeId = sourceNodeId;
    }
}

public async Task Handle(CacheInvalidationIntegrationEvent @event)
{
    // 1) ECHO GUARD: kendi yayınladığımız event'i de görürüz → kendi NodeId'mizi atla.
    if (@event.SourceNodeId == EventBusRemoteTagBroadcaster.NodeId)
    {
        _logger.LogTrace("[CacheBroadcast] Skip echo: tags=[{Tags}]", string.Join(",", @event.Tags));
        return;
    }

    foreach (var tag in @event.Tags)
    {
        try
        {
            // 2) CASCADE ÖNLEME: RemoveByTagLocallyAsync — sadece L1, tekrar broadcast YOK.
            await _cache.RemoveByTagLocallyAsync(tag);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "[CacheBroadcast] Local tag drop failed: tag={Tag}", tag);
        }
    }
}

{
  "Cache": {
    "BroadcastTagInvalidation": true
  }
}

// Application/DependencyInjection.cs — EventBus register edildikten SONRA
builder.Services.AddSingleton<IRemoteTagBroadcaster, EventBusRemoteTagBroadcaster>();