Day 18: Docker Compose!

What is Docker Compose?

Docker Compose is a tool that simplifies the process of defining and running multi-container Docker applications. You use a YAML file to configure your application’s services, networks, and volumes, and then spin them up with a single command.

What is YAML?

YAML stands for "Yet Another Markup Language".
It’s a human-readable data serialization language used for configuration files. YAML files typically have .yml or .yaml extensions.

Today’s Task: Docker Compose Configuration

Docker Compose File

version: '3.8'

services:
  backend:
    build:
      context: .
    ports:
      - "5000:5000"
    environment:
      MYSQL_HOST: mysql
      MYSQL_USER: admin
      MYSQL_PASSWORD: admin
      MYSQL_DB: myDb
    depends_on:
      - mysql

  mysql:
    image: mysql:5.7
    ports:
      - "3306:3306"
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: myDb
      MYSQL_USER: admin
      MYSQL_PASSWORD: admin
    volumes:
      - ./message.sql:/docker-entrypoint-initdb.d/message.sql
      - mysql-data:/var/lib/mysql

volumes:
  mysql-data:

Breakdown of the Configuration

Version

• version: '3.8': Uses Docker Compose file format version 3.8, compatible with Docker Engine 19.03.0+.

Services

1. Backend Service

    backend:
      build:
        context: .
      ports:
        - "5000:5000"
      environment:
        MYSQL_HOST: mysql
        MYSQL_USER: admin
        MYSQL_PASSWORD: admin
        MYSQL_DB: myDb
      depends_on:
        - mysql
   

   • build: Builds the Docker image for the backend service from the current directory (context: .).

   • ports: Maps port 5000 on the host to port 5000 in the container.

   • environment: Sets environment variables for the backend to connect to the MySQL database.

     • MYSQL_HOST: Hostname of the MySQL service (mysql).

     • MYSQL_USER, MYSQL_PASSWORD, MYSQL_DB: Credentials and database name for connecting to MySQL.

   • depends_on: Ensures the MySQL service starts before the backend service.

2. MySQL Service

    mysql:
      image: mysql:5.7
      ports:
        - "3306:3306"
      environment:
        MYSQL_ROOT_PASSWORD: root
        MYSQL_DATABASE: myDb
        MYSQL_USER: admin
        MYSQL_PASSWORD: admin
      volumes:
        - ./message.sql:/docker-entrypoint-initdb.d/message.sql
        - mysql-data:/var/lib/mysql
   

   • image: Uses the MySQL 5.7 image from Docker Hub.

   • ports: Maps port 3306 on the host to port 3306 in the container.

   • environment: Configures MySQL with root password, a default database, and a non-root user.

   • volumes:

     • ./message.sql:/docker-entrypoint-initdb.d/message.sql: Mounts a SQL file to initialize the database.

     • mysql-data:/var/lib/mysql: Persists MySQL data using a named volume.

Volumes

volumes:
  mysql-data:

• How to Set Up and Use the Volume

  Create the Volume

  1. • Before using the volume in your Docker Compose file, create it using:

          docker volume create mysql-data
       

How to Use This Configuration

1. Start Services

   • Run docker-compose up to start both backend and MySQL services. This command builds the backend image (if needed), starts the containers, and attaches them to a network

     

2. Inspect Services

   

3. Test the Application
   Open the browser and browse the Instace IP followed by port number 5000 mapped with the backend container

   

   Wow it's running

4. Check Logs

   • Use docker-compose logs to view logs from both services and ensure everything is running smoothly.

5. Stop Services

   • Run docker-compose down to stop and remove all containers, networks, and volumes defined in the docker-compose.yml file.

Happy Dockerizing! 😃

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