CQRS and Event Sourcing Implementation with Kafka and MySQL (JBDC)

Introduction

The aim of this small project is to illustrate the possibility of applying CQRS, Domain-Driven Design and Event Sourcing in a simple way, enabling Reactive architecture and leveraging Kafka as a distributed message broker

See: https://speakerdeck.com/vgoldin/es-and-kafka

Structure

Module	Purpose
services-core	core marker interfaces shared between all other modules
services-infrastructure-eventstore	event store implementation with JDBM 2.0
services-infrastructure-messaging	event publisher and command listener implementation with Kafka
services-intentoryitem-schema	json-schema's of all the events and commands used in API and Domain services
services-inventoryitem-api	API micro-service, exposing RESTfull API, creating Projectin with Hazelcast and dispatching commands to Kafka
services-inventoryitem-domain	Domain micro-service, encapsulating Aggregate Root, handling commands and publishing events

Pre-Requisities

• JDK 1.8
• Maven 3.3.x
• (optional) Docker (for Kafka)

Building

mvn clean install

Running Services

Kafka

docker run -p 2181:2181 -p 9092:9092 --env ADVERTISED_HOST=127.0.0.1 --env ADVERTISED_PORT=9092 spotify/kafka

API Micro-Service

cd services-inventoryitem-api/target
java -jar services-inventoryitem-api-1.0-SNAPSHOT.jar server classes/application.yml

Domain Micro-Service

with local jdbm database

cd services-inventoryitem-domain/target
java -jar services-inventoryitem-domain-1.0-SNAPSHOT.jar server classes/application.yml

with MySQL running on 127.0.0.1:3306 (see docker-compose.yml)

cd services-inventoryitem-domain/target
java -jar services-inventoryitem-domain-1.0-SNAPSHOT.jar server classes/application-jdbc.yml

Exposed APIs

GET     /inventory-items (io.plumery.inventoryitem.api.resources.InventoryItemResource)
POST    /inventory-items (io.plumery.inventoryitem.api.resources.InventoryItemResource)
GET     /inventory-items/events.stream (io.plumery.inventoryitem.api.resources.InventoryItemResource)
PUT     /inventory-items/{id} (io.plumery.inventoryitem.api.resources.InventoryItemResource)
POST    /inventory-items/{id}/deactivate (io.plumery.inventoryitem.api.resources.InventoryItemResource)

Swagger API

• Download swagger ui from https://github.com/swagger-api/swagger-ui
• Extract the zip
• Change to dist folder
• Open index.html
• Point to:

http://localhost:9901/swagger.json

Replaying Projection

• Download and unzip Kafka
• Change to KAFKA_HOME
• Stop API Micro-Service
• Execute the following command:

./bin/kafka-streams-application-reset.sh --application-id InventoryItemsDenormalizationApplication \
                                      --input-topics InventoryItem \
                                      --bootstrap-servers localhost:9092 \
                                      --zookeeper localhost:2181

TODO

• Get rid of ID.class
• Generate all the events and commands from JSON schema
• Add swagger documentation for API part
• Implement UI Micro-Service