1.1 Core Concepts of Docker Compose
Docker Compose is a tool for defining and running multi-container Docker applications. It lets you easily describe your app's architecture. Just like with Docker images, this is done in a text file called compose.yml, which follows specific rules. This file allows you to describe all of the containers, their connections, networks, and shared settings. Thanks to this, you can launch a multi-container app and manage all its components.
Core Concepts of Docker Compose
- defining services: Docker Compose lets you define all app components (e.g., web servers, databases, caches, and other services) in one config file.
- multi-container apps: Compose makes it easier to start and coordinate apps consisting of multiple containers.
- process automation: With Compose, you can automate the deployment, management, and scaling of all containers included in your app.
Why do you need Docker Compose?
- simplified management of complex apps: Modern apps often use multiple services running in separate containers. Docker Compose makes managing these services simpler.
- environment consistency: Docker Compose ensures the same environment setup for development, testing, and production, reducing the chances of errors caused by configuration differences.
- faster development: With Compose, you can easily start and stop all required services with just one command, speeding up the development and testing process.
- scalability: Docker Compose makes it easy to scale services, increasing the number of container instances as needed.
Important! Previously, Docker Compose was a standalone app, and all its commands started with "docker-compose …". But starting with Docker version 20 and above, Compose is integrated, and commands now start with "docker compose …".
So sometimes on the internet, you might come across examples using the old format "docker-compose", and sometimes the new "docker compose". Don't freak out, both versions work the same way.
Also, note that the config file can now be named either docker-compose.yaml or compose.yaml. Both versions are supported and function the same, but compose.yaml is used in newer Docker Compose versions.
1.3 Basic Docker Compose Commands
1. Starting the app
This command reads the compose.yaml (or docker-compose.yml) file, creates, and launches all the services defined in it.
docker compose up
2. Stopping the app
This command stops and removes all containers, networks, and volumes created using docker compose up.
docker compose down
3. Viewing logs
This command shows the logs of all services, making it easy to debug the app.
docker compose logs
4. Restarting services
This command restarts all or specified services, which is helpful when making changes to code or configuration.
docker compose restart
1.4 Using Docker Compose
Benefits of using Docker Compose
- easy deployment: with Docker Compose, you can deploy a complex app with a single command.
- dependency management: Compose automatically handles dependencies between services, ensuring they start in the right order.
- service isolation: each service runs in its own container, which ensures isolation and reduces the risk of conflicts between services.
- flexibility: Docker Compose supports different configurations for development, testing, and production, making it easier to manage environments.
Using Docker Compose
Docker Compose is widely used for:
- development: simplifies creating a consistent development environment that can be easily shared among the development team.
- testing: allows quickly setting up a test environment identical to production.
- production: simplifies deploying and managing multi-container apps in production environments.
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