Load-Balancing-5-replicas-with-nginx

This is a docker compose file that contains an nginx image and alpine image and I have connected them together.

NGiNX

Nginx (pronounced "engine x" /ˌɛndʒɪnˈɛks/ EN-jin-EKS, stylized as NGINX) is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache. The software was created by Igor Sysoev and publicly released in 2004. Nginx is free and open-source software, released under the terms of the 2-clause BSD license. A large fraction of web servers use Nginx, often as a load balancer.

Docker hub link for nginx

Alpine

Alpine Linux is a Linux distribution built around musl libc and BusyBox. The image is only 5 MB in size and has access to a package repository that is much more complete than other BusyBox based images. This makes Alpine Linux a great image base for utilities and even production applications. Read more about Alpine Linux here and you can see how their mantra fits in right at home with Docker images.

Docker hub link for alpine

Docker Compose Details

This Docker Compose setup includes an Nginx service and 5 Alpine replicas. It creates a web server using Nginx and connects it with the Alpine replicas. Each replica adds its own hostname to the index.html file.

The nginx service is :

nginx:
    image: nginx:latest
    container_name: nginx
    restart: unless-stopped
    ports:
      - 8080:80
    volumes:
      - alpine_data:/usr/share/nginx/html
    command: sh -c 'printf "Welcome!<br><p>This is an nginx project that connects 5 alpine replicas index.html<br>Say hi guys!</p>" > /usr/share/nginx/html/index.html && nginx -g "daemon off;"'
    networks:
      - vlab

Local used port is 8080 and container's port is 80, the alpine_data pointing /usr/share/nginx/html directory, after the command argument we accessing to Nginx's terminal and we add to index.html printf command and at the end nginx -g "daemon off;" this option ensures that the Nginx process runs in the foreground, allowing Docker to manage the container and enabling you to see the Nginx logs and keep the container running interactively. Finally the Nginx service joins to vlab network

The alpine service is :

  alpine:
    image: alpine:latest
    restart: unless-stopped
    volumes:
      - alpine_data:/var/www/html
    deploy:
      resources:
        limits:
          memory: 200M
          cpus: '0.3'
      replicas: 5
      update_config:
        parallelism: 1
        delay: 10s
        order: stop-first
      restart_policy:
        condition: on-failure
    environment:
      - MESSAGE=Hello from Alpine
    command: sh -c 'mkdir -p /var/www/html && printf "<br>$$MESSAGE $$HOSTNAME<br>"  >> /var/www/html/index.html && tail -f /dev/null'
    networks:
      - vlab

With memory forces the service use only 200mb of ram, cpus argument forces to use 0.3 power of the CPU, replicas creates 5 alpine services,MESSAGE variable gives the message Hello from alpine, command argument creates /var/www/html directory and prints the MESSAGE and HOSTNAME variable to the /var/www/html/index.html. Last but not least the tail -f /dev/null command is often used as a workaround or placeholder command in Docker containers to keep the container running indefinitely.

To create volume alpine_data and vlab network:

volumes:
  alpine_data:

networks:
  vlab:

Instalation guide

See INSTALL.md file or click here ;)