Load balancer example with Docker

docker-compose.yml

version: "3"

services:
  db:
    image: postgres:latest
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
      # ... other environment variables
  my-service:
    image: "my-service:latest"
    environment:
      DB_USER: user
      DB_PASSWORD: password
      # ... other environment variables
    depends_on:
      - db
    expose:
      - "5000"
  nginx:
    image: nginx:latest
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
    depends_on:
      - my-service
    ports:
      - "4000:4000"

nginx.conf

user  nginx;

events {
    worker_connections   1000;
}
http {
        server {
              listen 4000;
              location / {
                proxy_pass http://my-service:5000;
              }
        }
}

start

# fire up 5 service instances, automatically balanced
docker-compose up --scale my-servic=5