How to Create a Create a Multi-Container Application Using Docker Compose (Web + DB)| S-Logix

How to Create a Create a Multi-Container Application Using Docker Compose (Web + DB)?

Condition for Multi-Container Application Using Docker Compose (Web + DB)

Description:
This task demonstrate how to use Docker Compose to run a multi-container application. Specifically, you will deploy WordPress connected to a MySQL database using a single command. Docker Compose simplifies managing multiple containers and their dependencies.

Steps

STEP 1 — Create docker-compose.yml File
Description: Create a file named docker-compose.yml for WordPress and MySQL.
Command:

nano docker-compose.yml

Paste the following:

version: '3'
services:
  db:
    image: mysql
    container_name: mysqldb
    environment:
      MYSQL_ROOT_PASSWORD: pass
      MYSQL_DATABASE: wordpress  # optional, creates database automatically

  wordpress:
    image: wordpress
    ports:
      - "8083:80"
    depends_on:
      - db
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: root
      WORDPRESS_DB_PASSWORD: pass
      WORDPRESS_DB_NAME: wordpress

Notes:
✔ db service: Runs MySQL with root password pass.
✔ wordpress service: Runs WordPress and maps port 8083 on your host to port 80 in the container.
✔ depends_on: Ensures WordPress starts after MySQL is ready.

STEP 2 — Installation of Docker Compose
Description: Install Docker Compose and verify the version.
Commands:

sudo apt install docker-compose
docker-compose --version

sudo apt install docker-compose-plugin

STEP 3 — Start the Application
Description: Run the WordPress and MySQL containers in detached mode.
Command:
```
docker compose up -d
            
```
-d runs containers in background.
STEP 4 — Restart Containers
Description: After updating the Compose file, restart containers.
Commands:
```
docker compose down
docker compose up -d
            
```
✔ Wait a few seconds for MySQL to start before WordPress connects.
Open http://localhost:8083 → WordPress setup should load without errors.

STEP 5 — Configure WordPress Setup
Field & Example Values:

Field	Example Value	Notes
Site Title	My Test Blog	Can be anything, e.g., your project or blog name
Username	admin123	Must be alphanumeric, can include _, -, ., @
Password	StrongPass@123	Use a strong password; WordPress will warn if weak
Your Email	myemail@example.com	Used for admin notifications, password recovery
Search Engine Visibility	Leave unchecked	Optional, depends if you want search engines to index

Outcome
✔ A multi-container WordPress application running with a MySQL database.
✔ Managed entirely with Docker Compose, allowing easy start/stop with a single command.