Outbox Pattern with Debezium and NATS

Overview

This test project explores the implementation of the Outbox Pattern using Debezium to capture changes from an outbox table and NATS for streaming these events. The project comprises two main services:

• notification-service
• user-service

Each service is located in its respective directory, facilitating the simulation of domain event production and consumption through an outbox mechanism.

Services

• notification-service: Listens to events produced by the user-service using the outbox pattern. It subscribes to NATS subjects that correspond to outbox events and processes these events as they arrive.
• user-service: Generates domain events, stores them in an outbox table, and relies on Debezium to publish these events to NATS.

Setup

Outbox Table Creation

To initialize the outbox table for storing events, run the following SQL command:

CREATE TABLE outbox (
    id uuid NOT NULL,
    aggregatetype character varying(255) NOT NULL,
    aggregateid character varying(255) NOT NULL,
    type character varying(255) NOT NULL,
    payload jsonb NOT NULL,
    PRIMARY KEY (id)
);

Generating Sample Outbox Messages

Populate the outbox table with sample messages using this script:

BEGIN;

INSERT INTO outbox (id, aggregatetype, aggregateid, type, payload)
VALUES
(get_random_uuid(), 'TypeA', 'ID001', 'EventType1', '{"key":"value"}'),
(get_random_uuid(), 'TypeB', 'ID002', 'EventType2', '{"key":"value"}');

-- This will clear the outbox after inserting the messages to simulate message consumption
DELETE FROM outbox;

COMMIT;

Upon execution, events of type TypeA and TypeB will appear on outbox.event.TypeA and outbox.event.TypeB NATS subjects, respectively.