Kubernetes bills itself as a production-grade container orchestration tool. However, what does all of that mean? To understand, you have to go back in time to learn about the web hosting business. It's here that you'll learn how things developed, and what problems were solved by introducing Kubernetes.
What is Kubernetes?
You also have to understand what a container is, and how this type of hosting has evolved over time. Kubernetes was invented by Google to solve problems it had with its own infrastructure. A company like Google has hundreds of thousands of servers that it needs to manage, and it is in this backdrop that Kubernetes was created.
Let's break down all the terminology introduced above about Kubernetes. The first thing you need to know is that it manages containers. What is a container? A container is a method of isolating applications on a server, similar to a virtual private server (VPS). However, a container reuses the same Linux kernel for every instance. If one container were to crash the Linux kernel, it would bring down the whole system.
The dark days of web hosting involved first bare-metal, then virtual private servers. These methods of managing websites and services had a huge problem: They were expensive, yet they were not flexible or scalable enough to do a good enough job for most websites. For example, you had to pay for enough servers for the month, and if you needed more, you would have to pay on the spot for an additional month. You ended up using either too many or too few server resources for the amount of money you paid. Virtual server software solved part of this problem, but it was the same thing on a smaller scale. This is why cloud hosting and containerization came into play.
The problem with web hosting is that it isn't growing to your specific needs at that time. You can't provision the exact amount of server resources you will need at every instant. That's why you need to be able to acquire and release server resources at a moment's notice. Your website might have traffic spikes, but it might also have periods where there are very few people visiting. Why would you pay for all those resources when you aren't using them? Containers were created to manage this, and one of the most popular apps for managing containers is called Docker.
What problem does Kubernetes solve?
Since we're moving towards a future where we use containers instead of private servers or bare-metal servers, we will see tools like Kubernetes being used more often. What Kubernetes does is quite magical: It is an effective way of managing all of your container infrastructure in one simple-to-use application. Every Kubernetes tutorial starts out with this fundamental fact.
So, what is Kubernetes? It is a tool that helps you deploy, scale, and manage your applications with ease. It can do things like service discovery and load balancing, and you can even orchestrate your storage file systems. It automates DNS service, and it is self-healing. Kubernetes makes it possible for organizations to have only the infrastructure they need, when it is needed. This saves you a lot of money when you're not getting a lot of traffic, and will help your server stay up when it inevitably gets a few traffic spikes. When it comes to Kubernetes versus Docker, Kubernetes does a much better job as an open-source application, and you can even work with Docker in certain instances.
How does Kubernetes work?
The basic unit of Kubernetes is a cluster, which is a group of servers that work together to form a cohesive unit. You need to have one server in charge of managing the other servers, and then you have the notes that will actually run the containers. The master server is called the control plane. Each worker node hosts a group of containers in what is called a pod. Kubernetes then makes this system better by managing the control plane and the cluster across multiple nodes. This makes it resistant to one server crashing or physically dying. Here is what it looks like:
What are the components in Kubernetes?
The control plane has certain components that include an API server, a key-value store that is responsible for being a quasi-database, and a scheduler. There's also the controller manager, which is responsible for managing that service. You can also embed cloud-specific logic with the cloud controller manager.
Each node also has its own components that provide the runtime environment for Kubernetes. These components include kubelet, which is the agent that runs on each node, and is what actually manages the containers in the node to make sure that they're doing fine.
Then there is the proxy service, which maintains network rules for each node.
Finally, the most important piece of software on each node is a container runtime. This is the software that is actually responsible for running the container.
Kubernetes can actually have other add-ons as well, and you will frequently use them. Add-ons include DNS, a web user interface, container resource monitoring software, and finally, logging.
Why do you need Kubernetes?
Every company that has more than a few containers needs Kubernetes. It simplifies the work of managing and scaling your web backend. Without it, you will have to spend time using SSH to log in to every server to keep it up and running. Using something like Kubernetes will allow you to simplify your entire infrastructure, and require less staff on hand to manage everything.
Implementation stories
One of the world's leading digital travel companies was able to build its cloud infrastructure by using Kubernetes to manage it all. Another leading health service providing company was able to leverage Kubernetes to build its AI and machine learning computer infrastructure. The flexibility that Kubernetes provides could not be achieved with any other software.
