Scalable App Task 3: MongoDB Integration with Spring Boot and JMeter

Overview

This repository contains the implementation of Task 3 for the Architecture of Massively Scalable Applications course at the German University in Cairo, Department of Computer Science, under Assoc. Prof. Mervat Abu El-Kheir, Spring 2025. The task focuses on designing and implementing a NoSQL database schema using MongoDB, integrating it with a Spring Boot application, and managing entities such as Users and Posts with embedded and referenced relationships.

Project Description

The project includes:

• A MongoDB database schema with two main entities: User and Post.
• Relationships:
  • Document Referencing: Post references a User as its author.
  • Document Embedding: Post contains a list of embedded Comments.
• Custom repositories and service layer methods to handle CRUD operations and specific business logic.
• RESTful controllers to expose functionality via APIs.
• Dockerization with multiple services: application instances, MongoDB, Mongo Express, and Nginx.
• Load balancing using Weighted Round Robin with Nginx.
• Load testing using JMeter to evaluate system performance.

Features

Database Schema

• User: id (String), username (String), email (String).
• Post: id (String), title (String), content (String), author (User reference), comments (List of embedded Comments).
• Comment (embedded): text (String), date (String).

Repositories

• UserRepository: Extends MongoRepository for User entity management.
• PostRepository: Extends MongoRepository for Post entity management.

Services

• UserService:
  • Basic CRUD operations (pre-implemented).
  • Custom method: updateUserUsername – updates a user's username by ID with error handling.
• PostService:
  • Basic CRUD operations (pre-implemented).
  • getPostsByAuthorID: Retrieves posts by author ID with validation.
  • addCommentToPost: Adds a comment to a post by ID.

Controllers

• UserController:
  • Basic CRUD handlers.
  • PUT /updateUser to update a user's username.
• PostController:
  • Basic CRUD handlers.
  • GET /postsByUser/{id} to get posts by author ID.
  • POST /{postId}/comments to add a comment.
• MainController:
  • Handles database seeding and instance testing.

Dockerization

• Includes a docker-compose.yml with services:
  • Two Spring Boot app instances (named after your first and last name, e.g., random, student).
  • mongo for MongoDB.
  • mongo-express for MongoDB UI.
  • nginx as a load balancer.

Load Balancer (Nginx)

• nginx.conf configured with:
  • Upstream: YourName_52_1234.
  • Weighted Round Robin: weights of 2 and 1 for the two app instances.

Load Testing (JMeter)

• Test Plan: YourName_20_52_1234.jmx
  • 400 requests (last digit of ID × 100), 4 sec ramp-up.
  • Target: localhost, port 1234.
  • Request: GET to MainController's route.

Testing

• Public API tests included and can be run with:

  mvn test
  

(Uncomment test code if needed.)

Setup and Usage

1. Pre-Setup

• Ensure port 27017 is free for MongoDB.
• Follow CMS setup instructions if you're on Windows.

2. Configure Environment

• Edit application.properties:

  • ID=52-1234
  • Name=YourName

• Database name: YourName_52_1234.

3. Build and Run

mvn clean install
docker-compose up

• Seed the DB by hitting the seed endpoint via MainController.

5. API Endpoints

• /users: Basic CRUD
• /users/updateUser: PUT (update username)
• /posts: Basic CRUD
• /posts/postsByUser/{id}: GET posts by author
• /posts/{postId}/comments: POST comment to post

Skills Demonstrated

• Proficient in MongoDB NoSQL schema design.
• Expertise in Spring Boot REST API development.
• Document embedding and referencing in MongoDB.
• Docker Compose for scalable, multi-service apps.
• Load balancing with Nginx (Weighted Round Robin).
• Load testing with JMeter.
• Robust API design and error handling for production.

Submission

• Database Name: YourName_52_1234
• Port: 1234 (based on ID 52-1234)