spring-outbox-pattern

Description

How to solve the Dual Write problem using the Outbox Pattern with a pull and publish scheduler.

Dual Write problem

This project is a simple solution for the Dual Write problem.

The Dual Write problem happens when:

• the application needs to write to two different systems in a single transaction
• the systems have different transactional boundaries
• if one of the writes fails, the other write can't be rolled back, leaving the system in an inconsistent state

Example:

Write to a database and to a message broker.

The Dual Write problem can be solved using the Outbox Pattern, which makes sure that if one of the writes fails, the system can still recover the state inside the transaction and roll back all the writes.

Outbox Pattern implementation

There are probably different ways to implement the Outbox Pattern, but this simple project implements it using:

• a database table called outbox that contains all the messages that need to be sent to the message broker
• a scheduled task that reads the messages from the outbox table and sends them to the message broker

Then, once a service needs to write to the orders table, for example, it also writes to the outbox table in the same transaction.

Technologies used

• Java 21
• Spring Boot 3.3.2
• Spring Data JDBC
• PostgreSQL
• Docker Compose
• Kafka