janpetryk / cq-shop

An E-Commerce system based on microservices and event-driven communication.

CQ Shop

Intro

An e-commerce system written in a microservice architecture. Communication between applications is implemented mainly with events that are processed by Kafka

The following applications are domain services:

1. cart-service
2. logging-service
3. notification-service
4. order-service
5. user-management-service
6. warehouse-service

The following applications are infrastructure/application services:

1. api-service-gateway
2. config-server
3. eureka-server
4. schema-registry-server
5. Kafka
6. traffic-simulator

Technology Stack and Architecture

All the services are implemented with Java 11 and Spring Framework. Each application is built with Gradle. They use Config Server and Eureka Server.

The api-gateway-service is an application that runs as a Zuul Gateway. It delegates all the calls into proper services.

Current Architecture

Topics and Streams

All the domain applications publish to Kafka two kinds of messages:

1. domain events - messages that notify about a fact that has happened in the system, e.g. user account created.
2. commands/queries - messages related to CQRS implementation. Those messages are used to pass information within an application/service.

There are two main types of Kafka Topics:

1. service-name-events - topics for domain events. Domain services are allowed to listening to only those streams.
2. application-command-topic - a topic for command/queries messages

Messages format

All the messages are transferred as Avro Messages. The schema of all events is available in the avro/ directory. Microservices are using schema-registry-server to register and receive schema related information.

TODOs and tech debt

1. Cover services with unit tests.
2. Write integration tests. Consider Spring Cloud Contract.
3. Refactor traffic-simulator.
4. Do not use repositories in controllers. Push Queries and handle them in proper handlers.
5. Implement Event Sourcing for restoring applications' state.

Publications

1. CQ-Shop - introducing the project
2. CQ-Shop - Event Storming
3. CQ-Shop – Events and Anomaly Detection
4. CQ-Shop – Architecture, Environment, and Tools
5. CQ-Shop – Summary

Links

1. Trello Board
2. Gathered materials
3. Drive directory