From Docker Compose to Kubernetes

By Damian Velazquez Cafaro
From Docker Compose to #Kubernetes

There are multiple ways to deploy a cloud-native app in an efficient environment. Whether you have a single service or hundreds of microservices, you can configure your cloud cluster for maximum performance. The two most popular ways are by utilizing Kubernetes and Docker Compose, with the former being more popular in today’s market.

Docker Compose has its advantages compared to Kubernetes, but that doesn’t mean it is the best solution in the long run. Kubernetes is the more robust of the two when it comes to solutions that require scaling up and staying lean. Fortunately, migrating from Docker Compose to Kubernetes is a lot easier than ever before.

Why Move to Kubernetes?

As mentioned before, Docker Compose has some advantages over Kubernetes⁠⁠⁠—perhaps especially for those still new to containerization; the learning curve isn’t as steep with the former as it is with the latter. Docker Compose is designed from the ground up to simplify the deployment of microservices. You can use YAML to configure the cloud environment, and then deploy all pods and microservices with a single command. Sounds familiar?

Docker Compose has limitations that make Kubernetes more appealing as an option. For starters, Docker Compose is designed to run on a single host or cluster, while Kubernetes is more agile in incorporating multiple cloud environments and clusters.

That advantage alone means Kubernetes is easier to scale beyond a certain point. Support for elements like MySQL and GoLang is also better in Kubernetes, plus you can utilize native services from the likes of AWS and GCP to support your deployment.

It is clear though that the biggest reason to move to Kubernetes is flexibility. When you have reached a certain point with Docker Compose, moving to Kubernetes as your container runtime is the logical step to take. You can take your application to the next level with the migration.

Getting Started – The Challenges

There are some clear challenges to overcome before you can safely migrate your Docker Compose application to Kubernetes, the primary one being container-to-container communication. Remember that containers in Docker Compose are designed to run on a single host, which means inter-container communications require little to no special configuration.

That is not the case with containers running on multiple hosts or different cloud clusters. Communication between containers must be clearly defined – including through the establishment of a service mesh – in order for the application to work properly.

There is also the small refactoring that needs to be done in order to make your application friendlier to Kubernetes. After all, the migration is meant to allow the application to take complete advantage of Kubernetes’ strong points, and the only way to do that is by making small adjustments.

Lastly, there are compatibility challenges to think about. Most of the time, you have nothing to worry about when performing the migration. That said, Kubernetes handle low-level services in a slightly different way, so you might want to prepare for runtime errors while migrating.

To mitigate these challenges, there are several things you can do. That brings us to our next point.

Getting Started – Prerequisites

Now that you know the challenges you will face along the way it is time to prepare a few things for the migration. First, you want a Kubernetes cluster with RBAC enabled. If you want the Kubernetes cluster to be configured in a certain way, now is the time to do it. Reconfiguring the cluster after the migration is a lot harder to do.

You also want to have kubectl in your local computer or development server. Make sure kubectl can communicate with your deployment server (the cluster we prepared earlier) for a seamless migration. Docker is also required, especially in the development server or your local machine. A Docker Hub account is recommended.

Performing the Migration Using Kompose

The tool to use for migrating your Docker Compose to Kubernetes is Kompose. From your docker-compose.yml directory, simply run kompose convert and then kubectl apply -f <output file> to convert the docker-compose.yml to a kubectl-compatible file.

The rest should be easy from there since you can use kubectl to immediately deploy the newly converted Compose. You can run kubectl apply -f <config files> and immediately have the Docker Compose app running on Kubernetes.

Another way to migrate using Kompose is by performing kompose up directly. The up command immediately deploys your Docker Compose app to the designated cluster. Make sure your docker-compose.yml is configured properly.

You are halfway through the migration process. The next step is accessing the app once it is running in Kubernetes. You can use minikube for this purpose. If everything went well, you should see the services of your Docker Compose app running smoothly in Kubernetes.

Some troubleshooting may be required, especially if the Docker Compose application is not configured properly. Setting up a service mesh or reconfiguring how containers communicate with each other is the most common task to do at this point.

You also want to perform additional checks, particularly when it comes to access management and secrets. Depending on the cloud environment you use, you can either utilize a GUI console or a command-line interface to rearrange security and access.

Development and Deployment

Interestingly, you can build and push Docker images using the Github tool Kompose, which means the development environment doesn’t have to change. However, this may not be the most efficient way to go, especially when you consider the adjustments that need to be made every time you push a new Docker image.

Ideally, you want to make adjustments to your development environment after the initial migration is completed. You can pull the Kubernetes cluster to a local machine and set up your development environment that way. Alternatively, you can utilize other Kubernetes native tools to build a new and more efficient CI/CD pipeline.

One last thing to note about migrating from Docker Compose to Kubernetes: you’ll never look back. Kubernetes offers a lot of room for improvement and scaling up, and those who have migrated from Docker Compose to Kubernetes have found the new runtime to be much more flexible in nature. With the application running smoothly on Kubernetes, you can continue expanding its reach, performance, and functionality across multiple hosts. 
