Kubernetes vs. Docker – Which Should I use?
Using containers to manage applications has become an increasingly attractive choice for developers, but with so many choices it often begs the question – which should I use?
When researching which container management system to use, it’s common to see the ‘Kubernetes vs. Docker’ debate. This however, is somewhat of a misleading question!
In actuality, Kubernetes and Docker aren’t direct competitors. The two platforms are built around different concepts, to provide solutions to different problems.
Essentially, Docker is a containerisation platform, while Kubernetes is a container orchestrator which provides methods of managing container platforms like Docker. But since they both focus on the concept of containerisation, there is often confusion surrounding the platforms.
With that said, we hope to clear up confusion between the two, by explaining how each works and how they compare against each other.
Kubernetes vs. Docker: The benefits of using Containers
Both Kubernetes and Docker revolve around the idea of applications running in containers. Before we delve into the specifics of each platform, it’s important to understand what containers are intended for, and how you can benefit from using them.
One key benefit to using containers over traditional virtual machines is the reduced overhead on your system. Containers require less resources to be able to function since they don’t need to include an operating system, compared to VMs which each require a complete copy of an operating system.
Portability is also more easily achieved with containers. Applications running within containers can be effortlessly deployed to multiple operating systems and hardware platforms. Compatibility across platforms isn’t a concern.
Due to the isolated nature of containers, you can expect your operations to run much more smoothly too. If one application goes down, other containers running the same application will stay online without any technical issues.
Managing your application cluster is also very simple with the container system. Operations such as container creation, destruction, and replication can be done in a matter of seconds – which helps further speed up the development process.
What is Docker?
Docker is an open-source platform that uses operating system virtualisation to deploy software in lightweight, portable packages called containers. As well as deploying said containers, Docker also provides a variety of tools to help develop, ship and run applications running within them.
Containers are lightweight as they don’t require hypervisors to work, rather they run directly on the host machine’s kernel. While each container is isolated from any others with their own software, libraries and configuration files, they are also able to communicate with each other.
This architecture provides a fantastic platform for developers, with features that greatly simplify and streamline the entire application development process.
One of the other great features of Docker are images, which are essentially save states of a container. Thanks to this system, developers can rest assured that applications will run on any linux machine, regardless of any customised settings that machine might have.
Images can then be easily shared with anyone over the internet using the Docker Hub – an online library where users can download community-created Docker images, or upload their own.
How does it work?
When discussing Docker, usually people are referring to the Docker Engine, the client-server application that facilitates the creation and running of Docker containers.
Docker Engine can be broken down into three major components:
- A server, which is a form of long-running program called a daemon process, or the dockerd command
- A REST API, that specifies which interfaces programs can use to communicate with the daemon process
- A Command Line Interface (CLI) client, or the docker command
In practice, the CLI uses REST API to control the daemon process through direct CLI commands or scripting.
The daemon process then creates and manages the relevant Docker objects, like containers, images, networks and volumes.
What does it do well?
As we’ve touched on already, Docker excels at providing a straightforward method of bundling all the packages and configurations you need to run a software application within a portable container.
This container and image system greatly simplifies the process of building complex software applications. Multiple Docker containers can easily be combined to create more complicated systems, eliminating the need to manually build these individual functions.
For example – a complicated system might require a database server, application server, and web server to run side-by-side. Normally you would need to configure each of these individually. With Docker however, you can simply deploy pre-configured images of these applications, saving you lots of time and effort!
On top of this, you can also separate the requirements and dependencies for each type of server into their own respective container. Perhaps your database server requires a different version of a certain library, to your web server. Using Docker means you don’t need to worry about this.
The isolated nature of the container system also brings with it some security benefits. Since each container is separated, any security compromises will only affect that container, and not any other containers you may have. This can help stop any malicious third-parties in their tracks.
What doesn’t it do well?
As with all web technologies, there are a few downsides to using Docker.
First off is performance. Any virtualized environment comes with a performance penalty, and Docker is no exception. Running Docker containers side-by-side with an alternative hosted on a physical machine, will usually show the containers performing slightly slower. However this performance difference is often not even noticeable, and for many applications won’t make much of a difference.
That said, if latency and speed are absolutely paramount for your application, then Docker might not be your best option. It really all depends on what you’re developing!
Also if your application requires two services to be run on the same machine simultaneously, then there may be better alternatives. Docker isn’t designed to be used in this way and as such, the container system might not accommodate this particularly well.
What is Kubernetes?
Kubernetes is an open source container orchestration system, used for managing containerised systems and applications, with a focus on automation. Originally developed by Google, it intends to automate deployment, scaling, and availability of applications or services running in containers.
In simpler terms, it aims to provide better ways of coordinating and running applications within containers, across a cluster of machines.
As Kubernetes is used for managing containerised applications, it’s designed to work with a number of different types of containerization tools, including Docker. This is one of the key reasons it shouldn’t be considered a direct alternative – rather a system that can be used in conjunction with it.
In a production environment, Kubernetes is a fantastic choice due to the automated cluster management features provided. When used correctly, you can easily use the system to ensure that all of your applications are online, secure, and running efficiently.
How does it work?
At a basic level, Kubernetes connects individual physical or virtual machines into a cluster, using a shared network to allow communication between machines. This cluster is where all Kubernetes components, workloads and capabilities are configured.
In order to get a picture of how Kubernetes works, you should first understand two important terms.
The first is the node, which refers to the virtual machines and/or bare-metal machines that Kubernetes manages.
The second is the pod, which is a unit of deployment in Kubernetes referring to a collection of containers (commonly Docker-based) that need to coexist together. An example of a pod might be an application that relies on a combination of a web server and caching server containers. Both containers would be encapsulated side-by-side, in a single pod.
A simplified view of a Kubernetes could be broken down into 2 core components:
- A Master Node: this server acts as both the gateway and the brain of the cluster. The Master node is the primary point of contact with the cluster, and is responsible for much of the centralized functions Kubernetes provides. It also handles communication between other components in the cluster, as well as exposing an API to users and clients. All activities in the cluster are coordinated by the Master node.
- Working Nodes: these servers are responsible for running workloads using both local and external resources. Nodes receive work instructions from the master server, and then create or destroy containers accordingly. The nodes also adjust network rules, in order to route traffic to the appropriate destinations.
Each working node has a Kubelet, an agent that manages the node and communicates with the master node. The nodes are also usually equipped with tools for handling container operations, such as containerd and Docker.
Communication between the master node and working nodes is handled by the Kubernetes API. This API allows for querying and manipulation of objects within the Kubernetes architecture, like pods, namespaces, and events.
What does it do well?
Perhaps the best situation to use Kubernetes in, is a production environment. Due in part to the advanced automation features it offers, it can help streamline your day-to-day operations by handling much of the application management for you.
As well as ensuring that all of your applications are up and running, Kubernetes can also be configured to self-heal. Essentially this means that any unresponsive containers will automatically be replaced with new ones, which can help mitigate any significant outages.
Scaling your application is also made significantly easier with Kubernetes. Horizontal auto-scaling allows your cluster to adapt to any major increases in resource usage – for example Kubernetes might automatically start up new containers to handle CPU-intensive areas of your application when it’s under heavy load.
Kubernetes can also help simplify the deployment of your applications, whilst minimising downtime. Take for example, deploying a new version of your application. With Kubernetes, you can keep the existing version of your application running, while you deploy the new version. It’ll then ensure that the new version is working correctly, before taking the old version offline.
Of course these are just a brief look at some of the areas Kubernetes excels at – there are far too many to list here!
What doesn’t it do well?
While Kubernetes can indeed be hugely beneficial, it is of course not perfect by any means.
For many, Kubernetes can seem extremely complicated, and this is often considered to be one of it’s biggest drawbacks.
As we’ve covered already, Kubernetes is very powerful and can do a lot. However, in order to use it to its fullest, you’ll need to be prepared to put a lot of time into learning how it works, often through trial and error. This can prove frustrating for many when figuring out how to deploy an application.
Complexity with Kubernetes applies to more than just the initial setup however. After setting up the cluster, further management requires use of separate administrative tools like kubectl. Training your team on how to use such tools can reduce your team’s productivity, as they take the time to adjust to the new development workflow.
Transitioning to Kubernetes from a different platform can also be cumbersome and time-consuming. Software will need to be adapted to work smoothly on the platform, and some processes might need to be modified to work properly in the new environment. The amount of work required here will vary depending on the application, but it can often prove to be very challenging.
Lastly, if your application isn’t very complex, intended for a large audience, or requires a lot of computing resources, then Kubernetes might simply be overkill! If you’re just hosting a simple website or very basic application, then you shouldn’t be looking at Kubernetes as your first choice. Doing so will simply cost you more than it should – and it won’t necessarily bring many benefits!
Now that we’ve given an overview of Kubernetes and Docker, how they work, and their pros and cons, you should hopefully have a better idea of which platform to use.
However as we’ve explained throughout, the two platforms aren’t direct competitors, rather they are complementary of each other.
Kubernetes is very often used with Docker to great effect – Docker provides an excellent containerisation system for your applications to run on, and Kubernetes offers efficient ways of managing these containers. So, depending on the application you’re developing, you may well want to use both!
At UKHost4u we offer a variety of plans that are perfect for launching a Docker deployment, or managing a Kubernetes cluster. No matter what type of application you’re developing, our tools will help you streamline and improve every step of the development cycle.