CAP is an EventBus for .NET platform with Outbox pattern

published on 2022/11/23

Compared to other Services Bus or Event Bus, CAP has its own characteristics. It does not require users to implement or inherit any interface when sending messages or processing messages. It has very high flexibility. We have always believed that the appointment is greater than the configuration, so the CAP is very simple to use, very friendly to the novice, and lightweight.


This looks very interesting. It is something that we need to take a look more.

This is from Code Opinion

Distributed Transaction

When you’re using messages (events) to communicate between systems you will run into the situation where you need to save data to your database, then publish an event to a message broker. These events will then be received up by other systems for their own internal use.

The problem arises when two situations occur:

  • You save data to your database but there is a failure when publishing the event to your message broker
  • You publish an event to your message broker that something occurred in your system, but then when trying to save to your database, it fails.

In both situations, there is no consistency between what your database has saved and what you have published to the message broker.

What you want in this situation is one atomic transaction that can save data to your database and publish the event. If either fails, the other is rolled back. Basically, a distributed transaction. Outbox Pattern

The Outbox pattern solves this issue by using a single transaction to perform both actions. What this involves is rather than publishing the event directly to the message broker, it serializes the event and saves it to a table in the same database using the same transaction for persisting your application data.