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=== Part 3: ===

'''What is Docker Compose?'''

Docker Compose is a tool for defining and running multi-container Docker applications. With Compose, you can define a multi-container application in a single file, then spin up your application with a single command (docker compose up).

'''Key Concepts'''

    Services: Each container started by Docker Compose is a service. Services are defined in the compose.yaml file.
    Networks: By default, Docker Compose sets up a single network for your application. Each container for a service joins the default network and is discoverable via a hostname identical to the container name.
    Volumes: Volumes can be used to share files between the host and container or between containers.
 
'''Basic docker compose Commands'''

•	   ` docker compose up`: Starts up the services defined in the compose.yaml file.
•	   ` docker compose down`: Stops and removes all the containers defined in the compose.yaml file.
•	   ` docker compose ps`: Lists the services and their current state (running/stopped).
•	   `docker compose logs`: Shows the logs from the services.
 
'''Deploying !WordPress with Docker Compose'''

Let's deploy a !WordPress application using two containers: one for !WordPress and another for the MySQL database.
Create a compose.yaml file:


version: '3'

services:
  # Database Service
  db:
    image: mysql:5.7
    volumes:
      - db_data:/var/lib/mysql
    environment:
      MYSQL_ROOT_PASSWORD: somewordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress

  # WordPress Service
  wordpress:
    depends_on:
      - db
    image: wordpress:latest
    ports:
      - "8080:80"
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
      WORDPRESS_DB_NAME: wordpress
    volumes:
      - wordpress_data:/var/www/html

volumes:
    db_data: {}
    wordpress_data: {}


'''Start the !WordPress and Database Containers:'''Navigate to the directory containing the `compose.yaml` file and run:

`docker compose up -d`

This command will start the services in detached mode. Once the services are up, you can access the !WordPress site by navigating to `http://<MASTER_IP>:8080` from your browser.

'''Stopping the Services:''' To stop the services, navigate to the same directory and run:
 
'''docker compose down'''
 
Best Practices

* Explicit Service Names: Give your services explicit names to make it clear what each service does.

* Environment Variables: Use environment variables for sensitive information and configurations.

* Service Dependencies: Use the depends_on option to ensure services start in the correct order.