Load-Balancing-with-Nginx-Server

This repo demonstartes how ngnix server can be used as a load balancer and how client request can be balanced by distributing incoming client requests across multiple backend servers.

Working

Multiple FastAPI Containers

• Three instances of a FastAPI app (app1, app2, app3) run inside separate Docker containers.
• Each container runs Uvicorn on port 8000 internally.

Nginx as a Load Balancer

• Nginx is configured to balance incoming requests across the three containers.
• Nginx communicates with containers using Docker service names (app1, app2, app3) and container port 8000.
• Host ports (like 8001, 8002, 8003) are mapped for external access if needed, but Nginx uses internal ports for load balancing.

upstream app {
    server app1:8000;
    server app2:8000;
    server app3:8000;
}

server {
    listen 80;
    server_name _;

    location / {
        proxy_pass http://app;
    }
}

Docker Compose

• Manages all containers together: FastAPI apps and Nginx.

Testing Load Balancing

• A Python script (test_load.py) sends 10000 requests to Nginx (http://127.0.0.1:8000/).
• Each FastAPI container returns its hostname.
• The script counts how many requests each container handles:

{'0e526d71457f': 3334, '1fa129aab9fa': 3333, 'f601aba4acdf': 3333}

Requests are almost equally distributed, showing load balancing is working.

How to Run Locally

1. Python version

 3.9.13

2. Clone the Repository

git clone "https://github.com/Oudarja/Load-Balancing-with-Nginx-Server.git"

3. Set Up a Virtual Environment

python -m venv .venv
myenv\Scripts\activate

4. Install Dependencies

pip install -r requirements.txt

Build and start all containers:

docker compose up --build

Check Nginx logs to see requests being forwarded:

docker logs nginx

Test load distribution (optional):

python test.py