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RabbitMQ-based transactional outbox and inbox

This example implements the transactional outbox and inbox pattern to send an event message when a movie is created. It uses RabbitMQ for transporting the message. RabbitMQ is an open-source message-broker software that implements the Advanced Message Queuing Protocol (AMQP). In our example, it is used to exchange "movie_created" messages between the producer and the consumer applications.

Infrastructure

This service requires a PostgreSQL server to store the movies and to implement the transactional outbox and inbox pattern. And a RabbitMQ instance to send the messages. The root folder ./infra contains a docker-compose.yml file to create a local PostgreSQL and RabbitMQ instance for you. You can adjust the settings - especially the ports.

You can use the pgAdmin interface to check the database for the inbox and outbox tables as well as the movie tables. With the default settings, the URL is http://localhost:8084/ and the username and password are [email protected] and pgAdmin.

You can add the PostgreSQL server if you kept the defaults with the following details:

  • hostname: postgres
  • port: 5432
  • username: postgres
  • password: postgres

You can find the RabbitMQ management interface to check messages under the URL http://localhost:35672/ and the username and password are guest / guest if you use the defaults.

Setup

The producer and consumer services include a .env.template file in the project root folders and in the setup folders (four in total). You need to create a copy of them and store them as .env files. If you used the default infrastructure setup the env values are already prepared.

A setup:db script is included in the producer and consumer service. Please run it to set up the corresponding database, database roles, and table structure.

Run

The package.json files include a "dev:watch" and "debug:watch" for development and a "start" script that can be used after the project was built.

NOTE: In VSCode, for debugger to attach when using "debug:watch", set "Auto Attach" to "With Flag". If it is already set - change it to some other value, then back to "With Flag", and then re-open the terminal window.

Notes

The RabbitMQ connection is using Rascal to send and receive messages. This library is built on top of amqplib and adds a lot of options to make message delivery more resilient.

This example uses a rather minimalistic configuration. If you want to use it for production scenarios please check their documentation. You would at least need to configure redeliveries and retries, maybe add message encryption and other logic.