How to Use Docker Compose for Multi-Container Apps

Docker Compose is a tool that simplifies the management of multi-container applications using a single configuration file. With Docker Compose, you can define, run, and manage applications composed of multiple services. This tutorial will guide you through the steps to use Docker Compose effectively.

Prerequisites

• Docker installed on your system.
• Basic understanding of Docker and containers.

1. Installing Docker Compose

If Docker Compose is not installed, you can install it using the following commands. First, download the latest version of Docker Compose:

sudo curl -L "https://github.com/docker/compose/releases/latest/download/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

Next, set the permissions to make it executable:

sudo chmod +x /usr/local/bin/docker-compose

Finally, verify the installation:

docker-compose --version

2. Creating a Docker Compose File

The configuration for your multi-container application is defined in a file called docker-compose.yml. Create a new directory for your project and navigate into it:

mkdir myproject
cd myproject

Create a new docker-compose.yml file:

nano docker-compose.yml

Here’s an example configuration for a simple web application using Nginx and a Node.js backend:

version: '3'
services:
  web:
    image: nginx:latest
    ports:
      - "80:80"
    volumes:
      - ./html:/usr/share/nginx/html

  app:
    image: node:14
    working_dir: /usr/src/app
    volumes:
      - .:/usr/src/app
    command: npm start

This configuration creates two services: a web service with Nginx and an app service with Node.js.

3. Starting Your Application

To start your multi-container application defined in the docker-compose.yml file, run:

docker-compose up

This command will build and start all the containers defined in the file. Use the -d flag to run it in detached mode:

docker-compose up -d

4. Stopping Your Application

To stop the running containers managed by Docker Compose, use the command:

docker-compose down

This stops and removes all containers defined in your docker-compose.yml file.

5. Viewing Logs

You can view logs for your running containers using:

docker-compose logs

To view logs for a specific service:

docker-compose logs web

6. Scaling Services

Docker Compose allows you to scale services easily. For example, to scale the app service to run 3 instances, use:

docker-compose up --scale app=3

7. Conclusion

Docker Compose is a powerful tool for managing multi-container applications. By using a simple YAML file, you can easily define, deploy, and manage your services. Continue exploring advanced features like environment variables, networks, and custom configurations to leverage Docker Compose effectively for your projects.

About the Author

Dorian Kane

Author

View All Posts