How to convert Docker Compose applications to Kubernetes using Kompose (with examples)

Kompose is a powerful tool designed to facilitate the transition from Docker Compose to Kubernetes. As Kubernetes becomes more prevalent for container orchestration, many developers find themselves needing a straightforward way to deploy their existing Docker Compose applications into Kubernetes environments. Kompose simplifies this process by converting Docker Compose files into Kubernetes resource files, allowing for seamless integration and deployment within Kubernetes clusters.

Use case 1: Deploy a dockerized application to Kubernetes

Code:

kompose up -f docker-compose.yml

Motivation: Imagine you have been developing an application using Docker Compose on your local machine. The application consists of multiple interconnected services defined in a docker-compose.yml file. With Kubernetes providing enhanced scalability, management, and orchestration capabilities, you find it beneficial to deploy this application to a Kubernetes cluster. Using Kompose, you can directly convert and deploy your Docker Compose services to Kubernetes in one step, greatly simplifying the deployment process.

Explanation:

• kompose: The command-line tool that performs the conversion from Docker Compose to Kubernetes.
• up: This subcommand automatically converts the Docker Compose file and deploys the resultant Kubernetes resources to the cluster.
• -f docker-compose.yml: The -f flag specifies the Docker Compose file to be used for conversion and deployment. The file path should point to the existing docker-compose.yml file which describes the services and configurations of the application.

Example output: When this command is run, you’ll see output indicating that the services and deployments have been successfully created in Kubernetes. It will list each service and deployment, alongside its corresponding status, confirming that the application’s components have been instantiated in your Kubernetes cluster.

Use case 2: Delete instantiated services/deployments from Kubernetes

Code:

kompose down -f docker-compose.yml

Motivation: After experimenting with or running your application in the Kubernetes environment, there may arise a need to clean up and remove the deployed resources. This is helpful in development and testing scenarios where regularly starting and stopping different versions of applications is required. Using the kompose down command allows you to efficiently remove all the Kubernetes resources that were deployed using the associated docker-compose.yml file, maintaining a tidy cluster environment.

Explanation:

• kompose: The tool used for handling Docker Compose and Kubernetes transitions.
• down: This subcommand removes the Kubernetes resources that were previously created using the kompose up command.
• -f docker-compose.yml: The -f flag specifies the Docker Compose file used for the initial deployment, ensuring that the correct resources associated with this file are targeted for deletion.

Example output: Upon executing this command, the terminal will display messages confirming the deletion of various Kubernetes resources, such as services and deployments. It will closely mirror the list shown during deployment, confirming that these resources have been successfully removed from the cluster.

Use case 3: Convert a docker-compose file into Kubernetes resources file

Code:

kompose convert -f docker-compose.yml

Motivation: If you wish to take advantage of Kubernetes’ powerful orchestration features without immediately deploying your application, you can generate the necessary Kubernetes resource files for further customization or analysis. This approach allows developers to examine the generated YAML files and make specific adjustments or optimizations before deploying them to a Kubernetes cluster, ensuring the configuration meets specific operational requirements or standards.

Explanation:

• kompose: The tool that facilitates the conversion from Docker Compose to Kubernetes configuration files.
• convert: This subcommand does the heavy lifting of translating Docker Compose services into Kubernetes manifests. It writes out the Kubernetes YAML files but does not deploy them.
• -f docker-compose.yml: The -f flag indicates the Docker Compose file intended for conversion, forming a base for generating equivalent Kubernetes resource definitions.

Example output: Running this command will generate multiple YAML files corresponding to the services defined in your Docker Compose file. The terminal output will show the paths to these files, which typically reflect the service names. This output gives you the opportunity to review and modify these files if necessary, before manually deploying them to a Kubernetes environment using kubectl apply.

Conclusion:

Kompose stands out as an essential tool for developers looking to migrate their applications from Docker Compose to Kubernetes effortlessly. Its ability to convert, deploy, and clean up resources enables a streamlined workflow that aligns with modern DevOps practices. By leveraging Kompose, teams can harness Kubernetes’ robust capabilities, such as high availability and scalable deployment patterns, achieving new heights in application orchestration and management.