Defining and Running Multi-Container Applications with Docker Compose

Docker Compose is an essential tool for defining and running multi-container Docker applications. Docker Compose simplifies the Docker experience, making it easier for developers to create, manage, and deploy applications by using YAML files to configure application services.

Docker Compose provides several benefits:

• Lets you define multi-container applications in a single YAML file.
• Ensures consistent environments across development, testing, and production.
• Manages the startup and linking of multiple containers effortlessly.
• Streamlines development workflows and reduces setup time.
• Ensures that each service runs in its own container, avoiding conflicts.

Duration: 2.5 minutes

This Docker Compose demo shows how to orchestrate a multi-container application environment, streamlining development and deployment processes.

• Compare Docker Compose to the docker run command
• Configure a multi-container web app using a Compose file
• Run a multi-container web app using one command

Duration: 2.5 minutes

Do I need to maintain a separate Compose file for my development, testing, and staging environments?

You don't necessarily need to maintain entirely separate Compose files for your development, testing, and staging environments. You can define all your services in a single Compose file (compose.yaml). You can use profiles to group service configurations specific to each environment (dev, test, staging).

When you need to spin up an environment, you can activate the corresponding profiles. For example, to set up the development environment:

$ docker compose --profile dev up

This command starts only the services associated with the dev profile, leaving the rest inactive.

For more information on using profiles, see Using profiles with Compose.

How can I enforce the database service to start up before the frontend service?

Docker Compose ensures services start in a specific order by using the depends_on property. This tells Compose to start the database service before even attempting to launch the frontend service. This is crucial since applications often rely on databases being ready for connections.

However, depends_on only guarantees the order, not that the database is fully initialized. For a more robust approach, especially if your application relies on a prepared database (e.g., after migrations), consider health checks. Here, you can configure the frontend to wait until the database passes its health check before starting. This ensures the database is not only up but also ready to handle requests.

For more information on setting the startup order of your services, see Control startup and shutdown order in Compose.

Can I use Compose to build a Docker image?

Yes, you can use Docker Compose to build Docker images. Docker Compose is a tool for defining and running multi-container applications. Even if your application isn't a multi-container application, Docker Compose can make it easier to run by defining all the docker run options in a file.

To use Compose, you need a compose.yaml file. In this file, you can specify the build context and Dockerfile for each service. When you run the command docker compose up --build, Docker Compose will build the images for each service and then start the containers.

For more information on building Docker images using Compose, see the Compose Build Specification.

What is the difference between Docker Compose and Dockerfile?

A Dockerfile provides instructions to build a container image while a Compose file defines your running containers. Quite often, a Compose file references a Dockerfile to build an image to use for a particular service.

What is the difference between the docker compose up and docker compose run commands?

The docker compose up command creates and starts all your services. It's perfect for launching your development environment or running the entire application. The docker compose run command focuses on individual services. It starts a specified service along with its dependencies, allowing you to run tests or perform one-off tasks within that container.

• Overview of Docker Compose CLI
• Overview of Docker Compose
• How Compose works
• Using profiles with Compose
• Control startup and shutdown order with Compose
• Compose Build Specification