Swevo.AutoBus 1.0.0

AutoBus

Free, MIT-licensed message bus for .NET. No commercial license required — ever.

Why AutoBus?

MassTransit v9 is now a commercial product. AutoBus is a much smaller, focused alternative for the common case: a modular monolith (or a small set of services) that wants reliable pub/sub and point-to-point messaging with retry, without adopting a paid distributed messaging framework. It isn't a drop-in MassTransit replacement — there's no saga state machine engine, no routing slips, no multi-broker rider abstraction — just consumers, publish/send, retry, and (optionally) RabbitMQ.

public sealed class OrderCreated
{
    public int OrderId { get; init; }
}

public sealed class SendWelcomeEmail : IConsumer<OrderCreated>
{
    public Task Consume(ConsumeContext<OrderCreated> context)
    {
        // send the email...
        return Task.CompletedTask;
    }
}

services.AddAutoBus(cfg => cfg.AddConsumer<SendWelcomeEmail>());

// elsewhere:
await messageBus.PublishAsync(new OrderCreated { OrderId = 42 });

Install

dotnet add package Swevo.AutoBus

For cross-process messaging over RabbitMQ:

dotnet add package Swevo.AutoBus.RabbitMQ

Core concepts

• IConsumer<TMessage> — implement this for each message type you handle.
• IMessageBus.PublishAsync — fan-out to every registered consumer for a message type (zero consumers is not an error).
• IMessageBus.SendAsync — point-to-point; throws if zero or more than one consumer is registered for the message type.
• Retry — every consumer invocation runs through a Polly retry pipeline (exponential backoff, 3 attempts by default). Configure with cfg.UseRetry(retryCount, baseDelay).
• Transports — InMemoryTransport (default, in-process dispatch) or RabbitMqTransport/RabbitMqConsumerHost (cross-process, via Swevo.AutoBus.RabbitMQ).

RabbitMQ transport

services.AddAutoBus(cfg => cfg.AddConsumer<SendWelcomeEmail>());
services.AddAutoBusRabbitMq(options =>
{
    options.HostName = "localhost";
    options.QueuePrefix = "orders-service"; // scopes queue names per service
});

Publishing a message sends it to a fanout exchange named after the message's full type name. AddAutoBusRabbitMq also registers a hosted RabbitMqConsumerHost that declares and binds a durable queue for every locally-registered consumer, so the same IConsumer<T> code runs whether messages arrive in-process or over the broker — call AddAutoBusRabbitMq after AddAutoBus since it replaces the default in-memory transport.

Using AutoBus from an EF Core transactional outbox

AutoBus's IMessageBus.PublishAsync(object message, Type messageType, CancellationToken) overload mirrors MassTransit's IPublishEndpoint.Publish(object, Type, CancellationToken) signature, so it's a drop-in replacement inside an outbox processor loop — see EFCore.Outbox, which uses AutoBus instead of MassTransit for exactly this reason.

Design goals

• MIT licensed, forever. No commercial tier, no per-seat fees.
• Small surface area. Consumers, publish/send, retry — no bespoke DSL to learn.
• Same code, two transports. Consumers are written once; swapping InMemoryTransport for RabbitMqTransport is a one-line DI change.

Roadmap

• Saga/state-machine support and additional broker transports (Azure Service Bus, Amazon SQS) are being considered for future releases, scoped to real demand rather than parity with MassTransit's full feature set.

💼 Need .NET consulting?

I'm the author of AutoBus and a suite of compile-time source generators (AutoWire, AutoMap.Generator) and 28+ Polly v8 resilience packages. I'm available for consulting on Polly v8 resilience, Azure cloud architecture, and clean .NET design.

→ solidqualitysolutions.com · LinkedIn

Also by the same author

🌐 Full suite overview: swevo.github.io

License

MIT © Justin Bannister