Polling System with Kafka and WebSockets

A real-time polling system built with Kafka for message processing and WebSockets for real-time updates. This project allows users to create polls, vote on options, and view the results in real-time through a WebSocket connection. Additionally, the leaderboard feature ranks the top poll options across all active polls.

Features

• Create Polls: Users can create a poll with multiple options.
• Vote on Polls: Users can vote on poll options, with votes sent to Kafka for processing.
• Real-Time Updates: WebSocket connection allows clients to receive real-time poll updates and leaderboard changes.
• Leaderboard: Displays the top-ranking poll options across all active polls.

Tech Stack

• Node.js: Backend server
• Express.js: For serving APIs
• Kafka: For message processing and queue management
• WebSockets: For real-time communication between the client and server
• PostgreSQL: Database for storing poll and vote data

Getting Started

Prerequisites

Before running the application, ensure you have the following installed:

• Node.js (v12 or higher)
• Docker
• PostgreSQL

Docker Setup for Kafka and Zookeeper

You can easily run Kafka and Zookeeper using Docker.

1. Running Zookeeper

To run Zookeeper using Docker, run the following command:

docker run -p 2181:2181 zookeeper

2. Running Kafka

To run Kafka, use the following command (replace <YOUR IP> with your actual IP address):

docker run -p 9092:9092 -e KAFKA_ZOOKEEPER_CONNECT=<YOUR IP>:2181 -e KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://<YOUR IP>:9092 -e KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR=1 confluentinc/cp-kafka

Ensure that both Zookeeper and Kafka are running. You can check the logs to verify that Kafka has connected to Zookeeper and is ready to accept messages.

Setup

1. Clone the Repository

git clone https://github.com/yourusername/Polling-System-with-Kafka-and-WebSockets.git
cd Polling-System-with-Kafka-and-WebSockets

2. Install Dependencies

Run the following command to install the required dependencies:

npm install

3. Set Up PostgreSQL Database

Ensure PostgreSQL is running, and create a database for the polling system.

1. Create Database: Connect to PostgreSQL and create a new database:

   CREATE DATABASE polling_system;

2. Create Tables: Use the provided SQL scripts in the repository to set up the necessary tables (polls, poll_options, votes).

4. Configure Environment Variables

Create a .env file in the root of your project and add the following configurations:

PG_USER=your_postgres_user
PG_HOST=localhost
PG_DATABASE=polling_system
PG_PASSWORD=your_postgres_password
PG_PORT=5432

KAFKA_BROKER=<YOUR IP>:9092

• Replace <YOUR IP> with your actual local or external IP where Kafka is running.

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5. Running the Application

1. Start the WebSocket Server: In the root directory, start the application:

   npm start

2. The application will start and should be accessible at http://localhost:3000.

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6. API Endpoints

1. Create a Poll

• Endpoint: POST /api/polls

• Request Body:

  {
    "question": "What is your favorite programming language?",
    "options": ["JavaScript", "Python", "Java", "C++"]
  }

• Response:

  {
    "id": 1,
    "question": "What is your favorite programming language?",
    "created_at": "2024-11-25T12:34:56.789Z"
  }

2. Vote on a Poll

• Endpoint: POST /api/polls/:pollId/vote

• Request Body:

  {
    "pollOptionId": 2
  }

• Response:

  {
    "message": "Vote submitted successfully."
  }

3. Get Poll Results

• Endpoint: GET /api/polls/:pollId

• Response:

  [
    {
      "option_text": "JavaScript",
      "votes_count": 5
    },
    {
      "option_text": "Python",
      "votes_count": 3
    }
  ]

4. Get Leaderboard

• Endpoint: GET /api/leaderboard

• Response:

  [
    {
      "poll_id": 1,
      "option_text": "JavaScript",
      "votes_count": 5
    },
    {
      "poll_id": 2,
      "option_text": "Python",
      "votes_count": 3
    }
  ]

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7. Real-Time Updates via WebSockets

The WebSocket connection provides real-time updates for poll results and leaderboard changes.

WebSocket URL:

ws://localhost:8080

Messages Sent to Clients:

1. Poll Update (after each vote):

   {
     "pollId": 1,
     "results": [
       { "option_text": "JavaScript", "votes_count": 5 },
       { "option_text": "Python", "votes_count": 3 }
     ]
   }

2. Leaderboard Update:

   {
     "type": "leaderboard",
     "leaderboard": [
       { "poll_id": 1, "option_text": "JavaScript", "votes_count": 5 },
       { "poll_id": 2, "option_text": "Python", "votes_count": 3 }
     ]
   }

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8. Contributing

If you'd like to contribute to this project, follow these steps:

1. Fork the repository.
2. Clone your fork.
3. Create a new branch (git checkout -b feature-branch).
4. Make your changes and commit them.
5. Push to your fork and create a pull request.

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License

This project is licensed under the MIT License - see the LICENSE file for details.