Mastering Multi-Container Applications with Docker Compose

In the ever-evolving landscape of containerization, Docker Compose emerges as a versatile tool that simplifies the orchestration of multi-container applications. This hands-on guide takes you through the process of using Docker Compose to create a multi-container environment for a WordPress website and a Python file upload service. By the end of this journey, you’ll have a comprehensive understanding of how to harness the power of Docker Compose for your projects.

Step 1: Preparing Your Environment

Before you embark on the Docker Compose adventure, ensure you have a well-prepared environment:

1. Fire up an AWS EC2 instance with Docker already installed.
2. Let’s start fresh. Clean your Docker environment to eliminate any potential conflicts:

docker system prune -a -f -volumes

Step 2: Installing Docker Compose

In case Docker Compose isn’t already part of your toolkit, follow these installation steps:

1. Install Docker Compose by referring to the official Docker Compose Installation Guide. This ensures you have the latest version. If you’re using an EC2 instance with Ubuntu 22.04, Docker Compose is already pre-installed, saving you some effort.

sudo apt-get update sudo apt-get install docker-compose

To validate the installation, check the version of Docker Compose:

docker compose version

Step 3: Setting Up Your Project Directory

Create a new directory to serve as the home for your Docker Compose project. Download the essential project files into this directory:

mkdir docker-compose
cd docker-compose

wget https://tcb-bootcamps.s3.amazonaws.com/tcb5001-devopscloud-bootcamp/v2/module5-docker/files/module5-docker.zip
unzip module5-docker.zip
cd handsontask/volumes

In a Docker swarm environment go ahead to Craft the Docker compose file let’s gather a random alphanumeric password for MySQL database and MySQL root password and store it as a Docker secret with the name mysql_password and mysql_root_password respectively using docker secret create the command. To make the password shorter or longer, adjust the last argument of the openssl command. This is just one way to create a relatively random password.

$ openssl rand -base64 20 | docker secret create mysql_password -
$ openssl rand -base64 20 | docker secret create mysql_root_password -

List the secrets managed by Docker using docker secret ls:

docker secret ls

Another security best practice is to create an environmental variable and set the value pointing to an external source like a password manager

Learn more about security best practices here

In this scenario, we will just specify the password in the docker file.

Step 4: Crafting the Docker Compose File

The heart of your Docker Compose project is the Docker Compose YAML file, named docker-compose.yaml. This file serves as the blueprint for your application, defining services, networks, volumes, and their configurations.

The YAML file below sets up three services: a MySQL database for WordPress, the WordPress application itself, and a Python-based file upload service.

version: '3'
services:
  ctr-db:
    image: mysql:5.7
    volumes:
      - db-vol:/var/lib/mysql
    environment:
      MYSQL_ROOT_PASSWORD: wordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: devopscloudbootcamp
      MYSQL_PASSWORD: devopscloudbootcamp
    networks:
      - wp-net
    restart: always
  ctr-wp:
    image: wordpress:latest
    ports:
      - "8080:80"
    environment:
      WORDPRESS_DB_HOST: ctr-db:3306
      WORDPRESS_DB_USER: devopscloudbootcamp
      WORDPRESS_DB_PASSWORD: devopscloudbootcamp
      WORDPRESS_DB_NAME: wordpress
    networks:
      - wp-net
    restart: always
    depends_on:
      - ctr-db
  
  crt-py-upload-app:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8081:3000"
    volumes:
      - upload-files:/app/uploads
    restart: always
volumes:
  db-vol: {}
  upload-files: {}
networks:
  wp-net: {}

Step 5: Starting Your Docker Compose

It’s showtime! You’re ready to launch your multi-container application using Docker Compose:

docker compose up

In case you need to halt your Docker Compose environment, press CTRL + C.

To run Docker Compose in detached mode:

docker compose up -d

Step 6: Managing Your Docker Compose Services

• Verify the status of your Docker Compose services:

docker compose ps

• Administer your containers as needed:

docker compose stop 
docker compose start 
docker compose pause 
docker compose unpause

The pause command is useful in scenarios where you are trying to do an upgrade or change a setting in the application and you don’t want users to get access to it at that particular time. Once done you can up

Step 7: Exploring Your Docker Environment

Now that your Docker Compose environment is up and running, you can explore it further:

• List the running Docker containers:

docker ps

• Discover the Docker networks you’ve created:

docker network ls

• Examine the Docker volumes you’re working with:

docker volume ls

• Examine Logs to view activities being executed on our container environment managed by docker-compose and for troubleshooting purposes.

docker compose logs

Step 8: Cleaning Up Your Docker Compose

When you’ve accomplished your mission with Docker Compose, it’s good practice to wrap things up: This will stop the containers and remove the containers, volumes, and networks all created by Docker Compose for the upload files and database.

docker compose down -v

Docker Compose is a potent tool for managing intricate containerized applications. With this guide, you’ve mastered the art of orchestrating multi-container setups, greatly enhancing your development and testing workflows. Now, you’re ready to tackle your containerization projects with confidence. Happy containerizing! 🐳🚀