🚀 LeetCode Clone Setup Guide (Windows + WSL + Docker + PostgreSQL + Judge0)

Audience: CS students and developers building a LeetCode-style code execution platform using Express.js, PostgreSQL, Docker, WSL, and Judge0.

---

⚙️ Step 1: Setting Up WSL (Windows Subsystem for Linux)

1. Enable WSL

• Launch PowerShell as Administrator (right-click Start > Windows PowerShell (Admin)).

• Run this command:

    wsl --install
  

• This installs WSL with Ubuntu as the default Linux distribution.

2. Restart Your Computer

• WSL setup will prompt you to restart. Go ahead and do it.

3. Finish Ubuntu Setup

• Open Ubuntu from the Start menu.

• Set your UNIX username and password when prompted.

4. Update Ubuntu

sudo apt update && sudo apt upgrade -y

5. (Optional) Fix Docker compatibility with cgroup settings

sudo nano /etc/default/grub

• Change this line:

    GRUB_CMDLINE_LINUX="systemd.unified_cgroup_hierarchy=0"
  

• Save & exit (Ctrl + O, Enter, then Ctrl + X)

• Run:

    sudo update-grub
    sudo reboot
  

---

🐳 Step 2: Install Docker & Docker Compose on Ubuntu

1. Install Docker

sudo apt update && sudo apt install -y docker.io

2. Install Docker Compose

sudo apt install -y docker-compose

3. Start Docker Service (on every boot or manually)

sudo service docker start

---

🛢️ Step 3: Set Up PostgreSQL Database in Docker

1. Run PostgreSQL in Docker

sudo docker run --name my-postgres \
  -e POSTGRES_USER=myuser \
  -e POSTGRES_PASSWORD=mypassword \
  -p 5432:5432 -d postgres

⚠️ Avoid using special characters in passwords to prevent connection issues.

2. Check Container is Running

sudo docker ps

---

🔧 Step 4: Configure Prisma with PostgreSQL

1. Install Prisma

npm i prisma @prisma/client

2. Initialize Prisma

npx prisma init

• This creates a prisma/ folder and .env file.

3. Configure DATABASE_URL in .env

DATABASE_URL="postgresql://myuser:mypassword@localhost:5432/postgres"

4. Prisma Commands Flow

• Generate Prisma Client

    npx prisma generate
  

  Creates a client for interacting with your DB.

• Create Migration (optional for SQL schema)

    npx prisma migrate dev --name init
  

  Creates a new migration and pushes it to the DB.

• Push Prisma Schema to DB (no migration file)

    npx prisma db push
  

  Directly updates the DB with the schema (quick and dirty).

---

⚖️ Step 5: Setting Up Judge0 Code Execution Engine in WSL

1. Download Judge0

wget https://github.com/judge0/judge0/releases/download/v1.13.1/judge0-v1.13.1.zip

2. Unzip the Archive

unzip judge0-v1.13.1.zip
cd judge0-v1.13.1

3. Edit Judge0 Configuration

nano judge0.conf

Update the following:

REDIS_PASSWORD=yourredispassword
POSTGRES_PASSWORD=yourdbpassword

🔐 Use strong but simple passwords (no symbols like @, $, etc.).

4. Start Judge0 Services in Docker

• Start Redis and PostgreSQL first:

    sudo docker-compose up -d db redis
  

• Give it a moment:

    sleep 10s
  

• Start remaining services:

    sudo docker-compose up -d
    sleep 5s
  

5. Verify Installation

• Open your browser:

    http://localhost:2358/docs
  

• You should see the Swagger API UI of Judge0 ✅

---

🧠 Pro Tips

• Use Ctrl + C to stop any running service in the terminal.

• Use sudo docker-compose down to stop and remove containers.

• Don’t forget to use sudo service docker start when you reboot WSL.

• Use tools like Postman or REST Client to test Judge0 endpoints.

---

🧾 Final Thoughts

You’ve just built the backend infrastructure of a LeetCode-style app from scratch! Now go ahead and integrate it with Express.js or any frontend of your choice. The real fun (and bugs) begin now 😉

Happy Coding! 💻⚔️