The transactional outbox and transactional inbox patterns are used to ensure exactly-once processing of messages in event-driven architectures, where the loss or duplication of a message could have significant consequences. This library guarantees that a message is sent at least once, but processed exactly once, and is useful in scenarios where the reliability and atomicity of message processing is important. This pattern is an alternative to distributed transactions using a two-phase commit, which can lead to bottlenecks with a large number of microservices communicating with each other.
Message delivery via the PostgreSQL-based transactional outbox pattern
(generated with Midjourney)
This pg-transactional-outbox library implements the mentioned transactional
outbox and transactional inbox pattern for PostgreSQL. It stores the outgoing
messages reliably as part of your business logic DB transactions. It stores
incoming messages exactly once and lets your handlers process them exactly once.
The ./lib folder contains the pg-transactional-outbox library and unit
tests. You can find an introduction to the transactional outbox and inbox
pattern in the README.md. This should be your starting point.
You can find the integration tests in the ./__tests__ folder. This folder
includes outbox listener and inbox listener integration tests that use a
PostgreSQL instance for the actual tests. Check the
README.md file for further details.
The ./examples folder contains example implementations using actual message
brokers like RabbitMQ.
Currently, there is an example of how to implement the transactional outbox and inbox pattern when using RabbitMQ as the messaging broker. You can find more details in the README.md.