So just what is Kubernetes? Well first off, Kubernetes has to do with containers. The official Kubernetes website defines it as Kubernetes (K8s) is an open-source system for automating deployment, scaling, and management of containerized applications. Containers have been a buzzword for a while now as many companies have transformed into a container-centric infrastructure to host their applications. By doing so, it leaves behind the dependency on an underlying OS that adds complexity to virtualized host environments. Segregated within its container, the application operates under the illusion that it is getting its own dedicated OS instance. It’s also isolated from other applications hosted on the same server host. Containers offer more than just application segregation. Because container-based applications are independent of their host environment, you can distribute their self contained ecospheres around the world quickly and easily. Containerization is based on a three-part strategy:
- Transform an idea into a software application and package it
- Distribute it where you want in a scalable fashion
- Run it in its own isolated playground so it doesn’t interfere with other applications
Kubernetes is not a replacement for Docker
So let’s start out by saying what Kubernetes isn’t. Kubernetes is not a replacement for Docker. Kubernetes doesn’t create the actual containers themselves. It provides a platform to manage them. You don’t implement Kubernetes to create a container-centric infrastructure presence as Kubernetes is not a container hosting solution. That’s what Docker does. Docker is an open-source technology that makes it possible to run many applications on the same servers. It also makes it easy to package and ship applications. Millions of applications today reside within containers across the world and Docker has become the default container format. Like Docker, Kubernetes is a portable, extensible, open-source platform. What it does is make Docker better. Because they operate in tandem, the two often become incorrectly infused together. Kubernetes is a collaborative solution that you implement along with Docker. It is important to note that Kubernetes will work with any containerization technology, but we will use Docker as the de facto example.
Kubernetes is an Orchestrator
So how does Kubernetes make Docker better? Well, a key difference between the two is that Docker is a containerizing technology that makes applications easily shippable. It provides a container based foundation for your application environment. Kubernetes provides added features that are necessary in more complex multi-node environments.
Kubernetes is an orchestrator in the same way that software defined networking or virtual server farms need a cluster to operate. In fact, the name Kubernetes originates from Greek, meaning helmsman or pilot. A big part of its orchestration is resource management. Operating under a common resource management model, the components that makeup Kubernetes can work in conjunction to ensure that resources are neither underutilized nor oversubscribed. The Kubernetes orchestrator also ensures proper load balancing in order to uniformly spread the application load across multiple cluster nodes.
Who Needs Containerization?
If you have a stand-alone container environment with stable traffic, you may not have a need for Kubernetes. If however, you have a large enterprise with mission-critical apps residing on multi-node clusters, then Kubernetes can help you overcome challenges that inevitably occur in any complex application enterprise environment. For instance, let’s say one of your nodes goes down within your cluster. Suddenly you need to failover containers in order to avoid workload disruption. This is where Kubernetes takes over and saves the day. Kubernetes can help you multiple ways including:
- automate container provisioning
- ensure optimized load balancing
- automate failover and recovery
- ensure efficient scalability within large enterprises
To better understand Kubernetes, let’s review some of the primary components that make up the vocabulary and architecture of it.
- Pod – this is the smallest unit and serves as the basic building block of Kubernetes, which represents a running process on your cluster. A pod encapsulates one or more application containers along with its storage resources, IP address, and whatever options that it needs in order to function in your environment. It represents a single instance of an application.
- Worker Node – this can be either a virtual machine or a bare metal server. Worker nodes host the pods.
- Master Node – this is the managing node. The master node assigns pods to worker nodes.
The master node serves as the orchestrator that runs control plane components of the Kubernetes cluster. It makes global decisions concerning cluster operations and responds to cluster events. If suddenly you need many more containers fired up to satisfy an unexpected surge in demand for your hosted application, the master node takes charge of this. Not only does it spin up new containers, but assigns pods to containers in a way that maximizes efficiency and resources. In other words, it doesn’t just place containers, it places them in the ideal spot to ensure your application runs optimally. The same level of intelligence-based automation holds true if a node goes down. The master node also manages the scheduling of pods. By default, it schedules pods on nodes in a random fashion as resources are available. Kubernetes can take care of all of these governing functions far more effectively than human intervention. This makes your application infrastructure far more robust, able to overcome any possible disruption so that it doesn’t actually become one.
Kubernetes works very well within Azure application environments. In fact, all of the major cloud service providers support Kubernetes. At Xcelacore, we have years of experience working with container-based applications. Whether it’s creating software to be run in the most complex of environments or conducting extensive QA testing for multi-node container-based applications, we have the experience and expertise to ensure your applications achieve the performance and value that you expect.