Configuration as Code With docker-compose

In the realm of modern software development, the mantra "infrastructure as code" has become a cornerstone philosophy. With tools like Docker and Kubernetes, developers and users can define their infrastructure in code, ensuring consistency, reproducibility, and scalability. However, one area that often receives less attention is the configuration of the application itself. Enter Docker Compose — a powerful tool for defining and running multi-container Docker applications. Today, we'll explore the concept of Configuration as Code with Docker Compose and delve into its benefits.

What is Docker Compose?

Docker Compose is a tool for defining and running multi-container Docker applications. It allows developers to define a set of services, each running in its own container, and specify how these services interact with each other. Using a simple YAML file, developers can define the configuration of their entire application stack, including networking, volumes, environment variables, and more.

The Power of Configuration as Code

Traditionally, configuring an application stack involved manual intervention or the use of ad-hoc scripts. This approach is error-prone, hard to reproduce across machines, and difficult to maintain. Configuration as Code, on the other hand, brings the principles of version control, automation, and repeatability to the configuration of your application stack.

How Do I Use It?

Personally, I utilize Docker Compose to manage the many Docker containers running in my home lab. For each general category of application, I have a docker-compose.yml file describing how the applications should be set up and run. The only non-ephemeral data left is application configuration and the compose file, which can all be easily backed up with rsync to a remote server (remember the 3-2-1 rule!).

Example

Say you're wanting to create an instance of my Self-Hosted Bible server and want to make your configuration repeatable. Well here comes Docker Compose to the rescue. Included in the repo is this sample configuration:

  version: '3'
    services:
      self-hosted-bible-server:
        image: samhaswon/self-hosted-bible:latest
        container_name: self-hosted-bible
        ports:
          - "5000:5000"
        restart: always
        volumes:
          - /path/to/json/bibles:/usr/src/app/bibles/json-bibles
        environment:
          - ESV_API_KEY=<key-goes-here>

  

For configuration options, please see the Docker Compose documentation as there is too much for me to cover here. After you've written your compose file, just run "docker-compose up -d" to bring up your whole stack! It's truly an amazing piece of technology for simplifying your home lab. It even makes updating easier! You can use the command "docker-compose pull" to pull the latest images of all the container images in the stack. Then just run "docker-compose up -d" again to recreate any updated containers. But don't forget to remove old container images.

Conclusion

Docker Compose can and should be a key player in your home lab. It allows you to easily configure environments, networks, volumes, and more in a way that is easily versioned and backed up. Just write a quick little compose file and future you will be thankful. From backups to changing container hosts, Docker Compose is the way to go.