CNKart Microservices

Spring Boot microservice suite for a simple e-commerce workflow with separate services for catalog items, inventory checks, order placement, and service discovery.

Overview

CNKart started as a monolithic REST API and is now organized as a small microservice system. The split gives each business concern its own lifecycle, which makes the project easier to reason about and a better fit for distributed-systems learning.

The services work together like this:

• item manages catalog items.
• inventory checks stock availability for a requested SKU and quantity.
• order places orders after checking inventory and uses a fallback when inventory is unavailable.
• discovery-server acts as the Eureka registry for the service suite.

Concepts / Features Covered

• Spring Boot REST APIs
• Spring Data JPA persistence
• MySQL-backed service databases
• Eureka service discovery
• OpenFeign-based service-to-service communication
• Hystrix fallback handling in the order flow
• Service-local configuration files for each module
• Independent service startup and runtime lifecycle

Tech Stack

• Java 8
• Spring Boot 2.7.13
• Spring Cloud 2021.0.8
• Spring Web
• Spring Data JPA
• Spring Cloud Netflix Eureka
• Spring Cloud OpenFeign
• Spring Cloud Netflix Hystrix
• MySQL
• Lombok

Services

Service	Port	Responsibility
discovery-server	8761	Eureka registry for service registration
item	8081	Create and list catalog items
order	8082	Place orders after stock validation
inventory	8083	Check stock for a SKU and quantity

Example API Calls

Create an item

curl -X POST http://localhost:8081/api/item \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Wireless Mouse",
    "description": "2.4 GHz ergonomic mouse",
    "price": 799.00
  }'

Expected result:

201 Created

List items

curl http://localhost:8081/api/item

Sample response:

[
  {
    "id": 1,
    "name": "Wireless Mouse",
    "description": "2.4 GHz ergonomic mouse",
    "price": 799.00
  }
]

Check inventory

curl "http://localhost:8083/api/inventory?skuCode=1&qty=2"

Sample response:

true

Place an order

curl -X POST http://localhost:8082/api/order \
  -H "Content-Type: application/json" \
  -d '{
    "skuCode": "1",
    "price": 799.00,
    "quantity": 2
  }'

Success response:

Order Placed

Fallback response:

Item is not in stock, please try again later

Project Structure

cnkart/
├── discovery-server/
├── item/
├── inventory/
├── order/
├── README.md
├── CHANGELOG.md
└── .gitignore

Each service keeps its own pom.xml, mvnw, source tree, and configuration file so it can be built and run independently.

How to Run

1. Create the MySQL databases used by the services: item_service, inventory_service, and order_service.
2. Start discovery-server on port 8761.
3. Start inventory on port 8083.
4. Start item on port 8081.
5. Start order on port 8082.
6. Call the endpoints above from Postman, curl, or any REST client.

The local configuration files currently point to localhost MySQL settings, so update the database username and password if your environment differs.

Flow Diagram

flowchart LR
    Client[Client] --> Order["order-service :8082"]
    Client --> Item["item-service :8081"]
    Client --> Inventory["inventory-service :8083"]

    Discovery["discovery-server :8761"] --- Item
    Discovery --- Inventory
    Discovery --- Order

    Order --> Inventory
    Item --> ItemDB[(item_service DB)]
    Inventory --> InvDB[(inventory_service DB)]
    Order --> OrderDB[(order_service DB)]

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Learning Highlights

• Converting a monolith into a microservice suite
• Using Eureka to register and discover services
• Calling one service from another with OpenFeign
• Keeping order placement resilient with Hystrix fallback
• Separating service data, config, and startup responsibility
• Practicing REST, JPA, and distributed-system wiring in one repo

Notes

• The legacy monolithic CNKart codebase has been replaced by the microservice suite in this version.
• Configuration files are retained in each service folder for local setup.
• Build artifacts and IDE-specific files are intentionally excluded from the repository.