Kubernetes vs. Docker? Both have important roles for containerized apps

The question of Kubernetes vs. Docker is often raised when discussing cloud computing and containers. However, it’s not really a valid question. Kubernetes and Docker don’t compete. In fact, they are fundamentally different technologies that work well together for building, delivering, and scaling containerized apps.

Understanding how Kubernetes and Docker containerization fits into your app and web infrastructure is an important part of DevOps engineering.

First things first. What are containers?

When developers need to use a new application on a new computer, there are multiple steps to take first. Install the application. Configure it. Add a framework. Maybe even update the operating system.

What if there was a single package that had everything you needed? All the dependencies, settings, frameworks, and even security configurations already embedded in one nice, tidy, all-inclusive package. Or “container.” You just need to download it and run it.

Containerized applications have a single file, called an image, with all the dependencies, configuration, and frameworks embedded with it. A container’s most important benefit is portability — meaning that it can be run anywhere you need it. On your desktop. On your local server. In the cloud. It will always run the same way, regardless of the infrastructure. Containers isolate software from its environment and ensure that it works uniformly.

Just like shipping containers on cargo ships that use a standard size for storage and portability, software containers use a common platform for interoperability and portability.

Another benefit: Containers have an extremely small footprint. They only need an application and a definition of all required libraries. Unlike virtual machines, which each need a complete copy of a guest operating system, containers share the kernel of the host OS to virtualize the application.

Docker: The default container format

The idea of isolating environments is not new — and there are several types of containerization software. However, Docker has grown to be the default container format in recent years. Created by a company of the same name, Docker is open-source and features the Docker Engine. It allows developers to build and run containers on any development machine. Developers can then store or share container images through a container registry.

Most cloud providers support Docker — especially those offering infrastructure-as-a-service (IaaS) and serverless products. These providers run the Docker images and offer the underlying infrastructure for connected applications, such as web servers.

When developing cloud applications or microservices you often need to manage more than one software package. Your application might depend on separate databases, message systems, and so on. So, managing an environment where multiple packages and multiple containers are running can be difficult. Kubernetes helps us manage this complexity.

Kubernetes: The platform to manage containers

Originally created by Google but now managed by the Cloud Native Computing Foundation and community, Kubernetes is the platform that manages the containers your software needs to be stable and healthy. Sticking with the freight metaphor, Docker represents the containers and Kubernetes is the cargo ship.

Using Kubernetes YAML files developers turn infrastructure into code to describe the application and how containers should work. Kubernetes automates management tasks. It will deploy the containers, run the replicas to be executed, monitor container health, and provide the scale needed as demand increases. It will even upgrade to new versions when it’s available. Kubernetes is open-source and runs on a cluster of computers or virtual machines.

If a deployment goes wrong, Kubernetes makes it easy to roll back to the previous version. If a container becomes unstable, Kubernetes will automatically replace it with a new container, so that an application is always running and healthy. Although Kubernetes is typically used with Docker containers, you can use other container technologies. However, Kubernetes can (and does) benefit greatly from Docker.

Should I use Docker and Kubernetes?

If your app uses a microservice architecture or if you are looking to transition to this type of architecture, then Kubernetes will suit you well. It’s an especially good choice if you are already using containerization software like Docker. However, some organizations rush into using Kubernetes without understanding the basic concepts of a distributed system. They try to set up their own Kubernetes cluster and use it to host simple websites or a small scalable application. This is risky — because if you don’t have an in-depth knowledge of the system, things can break down easily.

Container technologies like Docker and Kubernetes are here to stay. They allow us to think about systems and applications in a new way — and are foundational to how we perform our DevOps engineering services. The two technologies complement each other and are continually changing to evolve.

Designing software for a container-centric platform makes your apps more scalable and more future-proof. Sticking to old VMs might work OK for now. In a few years, however, you will want to move to a containerized model.

Need help building apps that scale?

If you’re interested in learning more about how to implement container technologies with your app or web projects, we offer a full range of DevOps engineering services. Contact us to set up a time to talk — no strings attached.