Both Docker and Kubernetes (K8s) provide containerization services in the application development and deployment lifecycles, but they serve different functions. Docker is ideal for building and running a single container, while Kubernetes is suitable for scaling and managing containerized applications across multiple machine clusters. A container is typically an image file consisting of the tools, code, system libraries, and other software configuration that a microservice needs. So from the brief definition above, you can see that Docker comes in handy during the initial stages of software development, while Kubernetes kicks in later. Let’s compare these two in detail using microservices, which are the core components in software applications.

What Are Microservices?

Modern software applications consist of multiple microservices, where each microservice is an independent unit that runs each of the application’s processes as a service. So each service handles a single function in the application and they collectively communicate via APIs. Containerization provides the ability to pack these microservices as deployable programs on multiple platforms.

Where Docker Comes In

Docker provides an easy to use and efficient single container creation and management toolkit that gives developers the ability to run commands for container image file creation. As stated earlier, this image file contains all the code, software configurations, tools, and system libraries to run a microservice. So each microservice has a unique Docker image that can run it in any environment.

Where Kubernetes Comes In

An application’s design comprises multiple microservices, with some even having thousands that run on different servers. Remember, Docker is a single container creation and management toolkit. It isn’t meant to handle many of them. So how do you coordinate multiple, spread-out containers to run a single application? How do you group, schedule, and catalog them?

This task needs an orchestrator, similar to how the leader of a symphony orchestra coordinates multiple band members playing different musical instruments to produce a beautiful melody. Kubernetes is this orchestrator in software development.

Originally developed by Google, Kubernetes was open-sourced in 2014 and has become the industry standard in container orchestration and distributed app deployment.

How Kubernetes Works

Kubernetes bundles containers into a group that it manages on the same server to enhance resource usage efficiency and reduce network overload. An example of a Kubernetes managed container stack is an app server, sql database, and redis cache, while a Docker container is only one process in a Kubernetes cluster.

In each of these clusters, Kubernetes provides load balancing, service discovery, configuration management, self-healing, and automated rollouts/rollbacks, making it critical in the CI/CD pipelines required by DevOps teams.

Kubernetes Benefits

Infrastructure Abstraction

Kubernetes handles the compute resources, networking, and storage given to it on the developer’s behalf, so you have to only worry about writing the application and infrastructure code.

Automated Operations

Kubetcl, Kubernetes’ powerful command line tool and API, does most of the heavy lifting when it comes to automating tasks for container management, which ensures applications run exactly as intended.

Service Health Monitoring

Kubernetes runs automated health checks on the running microservices and restarts stopped or failed containers, so it only presents healthy running services that are ready to test or use. 

Kubernetes Disadvantages

Kubernetes is incredibly complex, which is why many developers and organizations prefer to use managed Kubernetes services from cloud operators. Additionally, the orchestrator is not a complete PaaS, so you still need to use other tools to build and manage Kubernetes clusters.

Docker vs. Kubernetes

When comparing the two, Docker is Kubernetes’ smaller brother responsible for creating and running a single container runtime. Kubernetes is the bigger brother that manages and handles multiple container runtimes, including the Docker ones. Think of an app vs. an operating system on a smartphone or computer. The two don’t compete on the same level. Their relationship is complimentary.

The direct competitor to Kubernetes in this case would be Docker Swarm, which is a similar container orchestration tool. This mode is available in Docker but is disabled by default.

Docker (in Swarm Mode) vs. Kubernetes

Both are declarative, use the YAML data serialization language to deploy applications, balance loads across containers in the clusters, scale automatically to the required system state, and provide access control/security across your services. However, Docker Swarm is easier to setup and configure when building and running your individual infrastructure (network, storage, and compute resources). The catch here is your individual infrastructure. So if you are not using the cloud or don’t need particular Kubernetes features, Docker Swarm is the better option.

Kubernetes, on the other hand, is the Linux of the cloud. Although complex to set up at the initial stages, the tool provides more features and better flexibility than Docker Swarm, such as:

• Managing network ingress
• Supporting multiple deployment strategies
• Providing visibility into the containers
• Broad support from a highly active open-source community

And to manage the complexity issue, most cloud vendors provide managed Kubernetes services to help organizations and developers get started quickly. So if you need cloud-native interoperability, run multiple clusters, and have many DevOps teams that need service and infrastructure isolations, Kubernetes is the better option.

Conclusion

The more apt comparison should be Docker Swarm vs. Kubernetes, but since Swarm mode is deactivated by default, we had to start from Docker as a container creation tool, then lead up to its orchestration feature. Docker can be used collaboratively with Kubernetes because each handles different functions. But this isn’t the case with Swarm. This orchestrator is more suitable for managing multiple containers when running them on individual infrastructure. If deploying them on the cloud, Kubernetes is better. And since most scalable applications nowadays run on the cloud, Kubernetes is inherently the better alternative all factors considered.

Rajesh Kumar

I’m a DevOps/SRE/DevSecOps/Cloud Expert passionate about sharing knowledge and experiences. I have worked at Cotocus. I share tech blog at DevOps School, travel stories at Holiday Landmark, stock market tips at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow , and SEO strategies at Wizbrand.

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