How to set up CAP with RabbitMQ in .NET Core?

Install the DotNetCore.CAP.RabbitMQ package, then configure it in Startup.cs using x.UseRabbitMQ() with the host name. The README provides code snippets for various transports, and you'll need to handle the database storage separately with a package like DotNetCore.CAP.SqlServer.

CAP vs MassTransit: which is better for microservices?

CAP is lighter and focuses on the Outbox Pattern for reliable messaging with a built-in dashboard, while MassTransit offers more advanced features like sagas and integration with more transports. Choose CAP for simplicity and guaranteed delivery, or MassTransit for complex workflow orchestration.

Does CAP support delayed messages without a message queue?

Yes, CAP has native support for delayed messages using its internal mechanisms, so you can publish messages with a delay without depending on features like RabbitMQ's delayed exchange, as shown in the PublishDelayAsync example.

How to monitor messages in the CAP dashboard?

Install the DotNetCore.CAP.Dashboard package and access it at the default path /cap. You can customize the path and integrate with service discovery for distributed environments, as detailed in the Dashboard section of the README.

What databases does CAP support for outbox storage?

CAP supports SQL Server, MySQL, PostgreSQL, and MongoDB (requiring 4.0+ cluster). You need to install the respective storage package and configure it in the setup, with the event log table integrated into your chosen database.

Is CAP suitable for high-throughput event processing?

CAP includes features like parallel processing and backpressure mechanisms for high throughput, but the Outbox Pattern adds database persistence overhead, which might bottleneck in extreme performance-critical applications compared to pure in-memory buses.

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CAP

MITC#v10.0.1

A .NET library for distributed transactions and event bus integration in microservices using the Outbox pattern.

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What is CAP?

CAP is a .NET library that provides a solution for distributed transactions and event bus integration in microservices. It ensures data consistency across services using the Outbox Pattern, guaranteeing that event messages are never lost even during system failures. It also functions as a high-performance, lightweight event bus for decoupled communication.

Target Audience

Developers and architects building .NET-based microservices or SOA systems who need reliable event-driven communication and distributed transaction handling.

Value Proposition

Developers choose CAP for its simplicity, reliability, and extensibility—it offers a unified solution for distributed transactions and event bus needs with support for multiple message queues and databases, a real-time dashboard, and built-in OpenTelemetry support.

Overview

Distributed transaction solution in micro-service base on eventually consistency, also an eventbus with Outbox pattern

Use Cases

Best For

Ensuring data consistency across microservices in distributed transactions
Building reliable event-driven architectures in .NET applications
Implementing the Outbox Pattern for guaranteed message delivery
Integrating heterogeneous systems with a pluggable message queue and database support
Monitoring and managing event flows with a built-in real-time dashboard
Handling delayed messages without relying on specific message queue features

Not Ideal For

Applications requiring ultra-low latency messaging without the overhead of database persistence
Teams already deeply integrated with alternative .NET messaging frameworks like MassTransit or NServiceBus
Systems where database access for message storage is prohibited or impractical
Projects needing complex, long-running saga orchestration beyond the basic outbox pattern

Pros & Cons

Pros

Pluggable Architecture

Supports a wide range of message queues like RabbitMQ, Kafka, and databases such as SQL Server and PostgreSQL, allowing flexible integration into diverse tech stacks as shown in the installation and configuration sections.

Real-time Monitoring Dashboard

Includes a built-in web dashboard for viewing message status and manually retrying failed messages, providing immediate visibility without third-party tools, as highlighted in the Key Features.

Guaranteed Delivery with Outbox

Implements the Outbox Pattern using a local message table to ensure messages are never lost, with automatic retries for failed deliveries, addressing reliability in distributed systems.

Native Delayed Messages

Offers built-in support for publishing messages with delays without relying on message queue features, demonstrated in the Publish with Delay example using PublishDelayAsync.

Cons

Azure Emulator Limitations

The README admits CAP cannot handle Azure Service Bus Emulator's separate ports simultaneously, requiring manual entity creation when AutoProvision is false, adding complexity for local development.

Database Overhead

The Outbox Pattern necessitates storing messages in a database table, which introduces additional writes and potential latency, impacting performance in high-throughput scenarios.

Setup Complexity

Requires installing and configuring multiple separate packages for transport and storage, which can be cumbersome and error-prone for simple or rapid prototyping needs.

Frequently Asked Questions

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