SlimMessageBus <!-- omit in toc -->

SlimMessageBus is a lightweight, flexible, and extensible messaging framework for .NET, supporting multiple message brokers, including Kafka, RabbitMQ, Azure EventHubs, MQTT, Redis Pub/Sub, and more. It simplifies asynchronous communication and integrates seamlessly with modern .NET applications.

See how to migrate from MediatR or MassTransit

🚀 Quick Start

Installation

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dotnet add package SlimMessageBus
# Add specific transport provider, e.g. Kafka
dotnet add package SlimMessageBus.Host.Kafka
# Add serialization plugin
dotnet add package SlimMessageBus.Host.Serialization.SystemTextJson

Basic Usage

Publishing Messages

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IMessageBus bus; // injected

public record OrderCreatedEvent(int OrderId);

await bus.Publish(new OrderCreatedEvent(123));

Consuming Messages

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public class OrderCreatedEventConsumer : IConsumer<OrderCreatedEvent>
{
    public async Task OnHandle(OrderCreatedEvent message, CancellationToken cancellationToken)
    {
        // Handle the event
    }
}

Request-Response Example

Sending a Request

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public record CreateCustomerCommand(string Name) : IRequest<CreateCustomerCommandResult>;
public record CreateCustomerCommandResult(Guid CustomerId);

var result = await bus.Send(new CreateCustomerCommand("John Doe"));

Handling a Request

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public class CreateCustomerCommandHandler : IRequestHandler<CreateCustomerCommand, CreateCustomerCommandResult>
{
    public async Task<CreateCustomerCommandResult> OnHandle(CreateCustomerCommand request, CancellationToken cancellationToken)
    {
        // Create customer logic
        return new(Guid.NewGuid());
    }
}

Configuration Example

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services.AddSlimMessageBus(mbb =>
{
    mbb.AddChildBus("Bus1", builder =>
    {
         builder
               // the pub-sub events
               .Produce<OrderCreatedEvent>(x => x.DefaultPath("orders-topic"))
               .Consume<OrderCreatedEvent>(x => x.Path("orders-topic")
                  //.WithConsumer<OrderCreatedEventConsumer>() // Optional: can be skipped as IConsumer<OrderCreatedEvent> will be resolved from DI
                  //.KafkaGroup("kafka-consumer-group") // Kafka: Consumer Group
                  //.SubscriptionName("azure-sb-topic-subscription") // Azure ServiceBus: Subscription Name
               )

               // the request-response
               .Produce<CreateCustomerCommand>(x => x.DefaultPath("customer-requests"))
               .Handle<CreateCustomerCommand, CreateCustomerCommandResult>(x => x.Path("customer-requests"))

               // Use Kafka transport provider (requires SlimMessageBus.Host.Kafka package)
               .WithProviderKafka(cfg => cfg.BrokerList = "localhost:9092");

            // Use Azure Service Bus transport provider
            //.WithProviderServiceBus(cfg => { ... }) // requires SlimMessageBus.Host.AzureServiceBus package
            // Use Azure Event Hub transport provider
            //.WithProviderEventHub(cfg => { ... }) // requires SlimMessageBus.Host.AzureEventHub package
            // Use Redis transport provider
            //.WithProviderRedis(cfg => { ... }) // requires SlimMessageBus.Host.Redis package
            // Use RabbitMQ transport provider
            //.WithProviderRabbitMQ(cfg => { ... }) // requires SlimMessageBus.Host.RabbitMQ package

            // Use in-memory transport provider
            //.WithProviderMemory(cfg => { ... }) // requires SlimMessageBus.Host.Memory package
   })
   // Add other bus transports (as child bus for in memory domain events), if needed
   //.AddChildBus("Bus2", (builder) => {  })
   .AddJsonSerializer() // requires SlimMessageBus.Host.Serialization.SystemTextJson or SlimMessageBus.Host.Serialization.Json package
   .AddServicesFromAssemblyContaining<OrderCreatedEventConsumer>();
});

The configuration can be modularized (for modular monoliths).

📖 Documentation

• Introduction
• Transports:
  • Amazon SQS/SNS
  • Apache Kafka
  • Azure EventHubs
  • Azure ServiceBus
  • Hybrid
  • MQTT
  • Memory
  • NATS
  • RabbitMQ
  • Redis
  • SQL
• Plugins:
  • Serialization
  • Transactional Outbox
    • MongoDB
  • Validation using FluentValidation
  • AsyncAPI specification generation
  • Consumer Circuit Breaker
• Samples
• Use Cases

📦 NuGet Packages

Name	Description	NuGet
SlimMessageBus	The core API for SlimMessageBus
Transports
.Host.AmazonSQS	Transport provider for Amazon SQS / SNS
.Host.AzureEventHub	Transport provider for Azure Event Hubs
.Host.AzureServiceBus	Transport provider for Azure Service Bus
.Host.Kafka	Transport provider for Apache Kafka
.Host.MQTT	Transport provider for MQTT
.Host.Memory	Transport provider implementation for in-process (in memory) message passing (no messaging infrastructure required)
.Host.NATS	Transport provider for NATS
.Host.RabbitMQ	Transport provider for RabbitMQ
.Host.Redis	Transport provider for Redis
.Host.Sql (pending)	Transport provider implementation for SQL database message passing
Serialization
.Host.Serialization.Json	Serialization plugin for JSON (Newtonsoft.Json library)
.Host.Serialization.SystemTextJson	Serialization plugin for JSON (System.Text.Json library)
.Host.Serialization.Avro	Serialization plugin for Avro (Apache.Avro library)
.Host.Serialization.Hybrid	Plugin that delegates serialization to other serializers based on message type
.Host.Serialization.GoogleProtobuf	Serialization plugin for Google Protobuf
Plugins
.Host.AspNetCore	Integration for ASP.NET Core
.Host.Interceptor	Core interface for interceptors
.Host.FluentValidation	Validation for messages based on FluentValidation
.Host.Outbox.PostgreSql	Transactional Outbox using PostgreSQL
.Host.Outbox.PostgreSql.DbContext	Transactional Outbox using PostgreSQL with EF DataContext integration
.Host.Outbox.Sql	Transactional Outbox using MSSQL
.Host.Outbox.Sql.DbContext	Transactional Outbox using MSSQL with EF DataContext integration
.Host.Outbox.MongoDb (beta)	Transactional Outbox using MongoDB
.Host.AsyncApi	AsyncAPI specification generation via Saunter
.Host.CircuitBreaker.HealthCheck	Consumer circuit breaker based on health checks

Typically the application layers (domain model, business logic) only need to depend on SlimMessageBus which is the facade, and ultimately the application hosting layer (ASP.NET, Console App, Windows Service) will reference and configure the other packages (SlimMessageBus.Host.*) which are the messaging transport providers and additional plugins.

🎯 Features

• Supports multiple messaging patterns: pub/sub, request-response, queues
• Compatible with popular brokers: Kafka, RabbitMQ, Azure EventHubs, MQTT, Redis, and more
• Fluent API for easy configuration
• Plugin architecture for serialization, validation, outbox patterns and interceptor pipeline
• Integration with .NET dependency injection
• Modern async/await support
• Minimal external dependencies
• SourceLink support
• Because SlimMessageBus is a facade, chosen messaging transports can be swapped without impacting the overall application architecture.

🚧 Contributing

We welcome contributions! See CONTRIBUTING.md for details on submitting issues, feature requests, and pull requests.
See here.

💬 Community

• Raise issues, discussions, questions and feature requests here.

📜 License

SlimMessageBus is licensed under the Apache License 2.0.

🙌 Credits

Special thanks to:

• Our maintainers
• Gravity9 for Azure infrastructure support.
• Redis Labs, CloudKarafka, HiveMQ, CloudAMQP for providing infrastructure for testing.