Docker Compose Tutorial with Examples

Introduction :

Docker Compose is a tool for defining and running multi-container Docker applications. It allows you to describe your application’s services, networks, and volumes in a docker-compose.yml file and then deploy and run the entire application stack with a single command. This tutorial will guide you through the basics of Docker Compose with practical examples.

Prerequisites:

• Docker installed on your system. You can download it from here.

Step 1: Create a Docker Compose File

Create a file named docker-compose.yml in your project directory. This file will define the services, networks, and volumes for your application.

version: '3'
services:
  web:
    image: nginx:alpine
    ports:
      - "80:80"
  database:
    image: postgres:latest
    environment:
      POSTGRES_PASSWORD: mysecretpassword

In this example, we define two services: web and database. The web service uses the Nginx image and exposes port 80. The database service uses the latest PostgreSQL image and sets a password for the PostgreSQL server.

Step 2: Run the Docker Compose Application

Open a terminal and navigate to the directory where your docker-compose.yml file is located. Run the following command to start the application:

docker-compose up

This command pulls the necessary images, creates containers, and starts the defined services. You should see logs from each service in the terminal.

Step 3: Access the Application

Open a web browser and navigate to http://localhost. You should see the default Nginx welcome page.

Step 4: Stop and Remove the Containers

To stop the running containers and remove them, press Ctrl + C in the terminal where docker-compose up is running. Alternatively, you can run:

docker-compose down

This command stops and removes the containers, networks, and volumes defined in your docker-compose.yml file.

Advanced Features:

1. Environment Variables:

You can use environment variables in your docker-compose.yml file. Update the web service to use a custom index page:

services:
  web:
    image: nginx:alpine
    ports:
      - "80:80"
    environment:
      - NGINX_INDEX=custom_index.html

2. Volume Mounting:

Mount a local directory into a container. Update the web service to include a volume:

services:
  web:
    image: nginx:alpine
    ports:
      - "80:80"
    volumes:
      - ./html:/usr/share/nginx/html

Create an html directory in your project directory and place a custom HTML file inside.

3. Networking:

Define a custom network for your services. Update the docker-compose.yml file:

version: '3'
services:
  web:
    image: nginx:alpine
    ports:
      - "80:80"
    networks:
      - mynetwork
  database:
    image: postgres:latest
    environment:
      POSTGRES_PASSWORD: mysecretpassword
    networks:
      - mynetwork
networks:
  mynetwork:

This creates a custom network named mynetwork and connects both services to it.

Conclusion:

Docker Compose is a powerful tool for defining and managing multi-container Docker applications. This tutorial covered the basics, and you can explore more features and options in the official documentation. As you work with Docker Compose, you’ll find it invaluable for simplifying the deployment and orchestration of your containerized applications.