Kubernetes or K8s

Kubernetes also known as K8s was built by Google based on their experience running containers in production. It is now an open-source project and is arguably one of the best and most popular container orchestration technologies out there. To understand Kubernetes, we must first understand two things – Container and Orchestration. Once we get familiarized with both of these terms we would be in a position to understand what kubernetes is capable of. We will start looking at each of these next. 

Containers

What are containers? Why do we need containers?

The most popular container technology out there – Docker. Let me start by sharing one example how I got introduced to Docker. In one of my previous projects, I had this requirement to setup an end-to-end stack including various different technologies like a Web Server using NodeJS and a database such as MongoDB/CouchDB, messaging system like Redis and an orchestration tool like Ansible. We had a lot of issues developing this application with all these different components. First, their compatibility with the underlying OS. We had to ensure that all these different services were compatible with the version of the OS we were planning to use. There have been times when certain version of these services were not compatible with the OS, and we have had to go back and look for another OS that was compatible with all of these different services.

Secondly, we had to check the compatibility between these services and the libraries and dependencies on the OS. We have had issues where one service requires one version of a dependent library whereas another service required another version. The architecture of our application changed over time, we have had to upgrade to newer versions of these components, or change the database etc and every time something changed we had to go through the same process of checking compatibility between these various components and the underlying infrastructure. This 9 compatibility matrix issue is usually referred to as the matrix from hell. Next, every time we had a new developer on board, we found it really difficult to setup a new environment. The new developers had to follow a large set of instructions and run 100s of commands to finally setup their environments. They had to make sure they were using the right Operating System, the right versions of each of these components and each developer had to set all that up by him/herself each time. We also had different development test and production environments. One developer may be comfortable using one OS, and the others may be using another one and so we couldn’t guarantee the application that we were building would run the same way in different environments. So all of this made our life in developing, building and shipping the application really difficult.

So I needed something that could help us with the compatibility issue. And something that will allow us to modify or change these components without affecting the other components and even modify the underlying operating systems as required. And that search landed me on Docker. With Docker I was able to run each component in a separate container – with its own libraries and its own dependencies. All on the same VM and the OS, but within separate environments or containers. We just had to build the docker configuration once, and all our developers could now get started with a simple “docker run” command. Irrespective of what underlying OS they run, all they needed to do was to make sure they had Docker installed on their systems.

So what are containers? Containers are completely isolated environments, as in they can have their own processes or services, their own network interfaces, their own mounts, just like Virtual machines, except that they all share the same OS kernel.  But its also important to note that containers are not new with Docker. Containers have existed for about 10 years now and some of the different types of containers are LXC, LXD , LXCFS etc. Docker utilizes LXC containers. Setting up these container environments is hard as they are very low level and that is where Docker offers a high-level tool with several powerful functionalities making it really easy for end users like us.

Container Orchestration

We now have our application packaged into a docker container. But what next? How do you run it in production? What if your application relies on other containers such as database or messaging services or other backend services? What if the number of users increase and you need to scale your application? You would also like to scale down when the load decreases. To enable these functionalities you need an underlying platform with a set of resources. The platform needs to orchestrate the connectivity between the containers and automatically scale up or down based on the load. This whole process of automatically deploying and managing containers is known as Container Orchestration.

Kubernetes is thus a container orchestration technology. There are multiple such technologies available today – Docker has its own tool called Docker Swarm. Kubernetes from Google and Mesos from Apache. While Docker Swarm is really easy to setup and get started, it lacks some of the advanced autoscaling features required for complex applications. Mesos on the other hand is quite difficult to setup and get started, but supports many advanced features. Kubernetes - arguably the most popular of it all – is a bit difficult to setup and get started but provides a lot of options to customize deployments and supports deployment of complex architectures. Kubernetes is now supported on all public cloud service providers like GCP, Azure and AWS and the kubernetes project is one of the top ranked projects in Github. 

Kubernetes Advantage

There are various advantages of container orchestration. Your application is now highly available as hardware failures do not bring your application down because you have multiple instances of your application running on different nodes. The user traffic is load balanced across the various containers. When demand increases, deploy more instances of the application seamlessly and within a matter of second and we have the ability to do that at a service level. When we run out of hardware resources, scale the number of nodes up/down without having to take down the application. And do all of these easily with a set of declarative object configuration files. 

And THAT IS Kubernetes. It is a container Orchestration technology used to orchestrate the deployment and management of 100s and 1000s of containers in a clustered environment.