Introduction

Imagine being a tech startup, with a revolutionary solution capable of managing a major issue. Just as you are about to deploy your intellectual creative, you find a major bug that disrupts the whole credibility of your application. It is definitely not worth the effort, right?  

In another scenario, you are well aware of the power of containerization, and you built your application in different containers. Even if a bug shows up, or you need to deploy only a part of the application the process would be hassle-free. Kubernetes is what helps you achieve this with much ease. 

But before breaking down the concept of Kubernetes, we first need to understand its fundamental concepts viz a viz Containerization and Orchestration. 

Containerization: 

Containerization came into picture with businesses realizing the importance of microservice, which is an approach to designing and building software applications as a collection of small, independent, and loosely coupled services. This gave way for containerization which involves the practice of packaging applications and their dependencies into lightweight, portable containers that can run consistently across various cloud environments and infrastructure.  

Containers are a way to virtualize the application and its runtime environment, making it easier to develop, deploy, and manage software in the cloud.  

Orchestration: 

With containerization comes orchestration which, in the context of computing and technology, refers to the automated coordination and management of multiple tasks, processes, or components to achieve a specific outcome or workflow. It involves ensuring that these tasks or components work together in a harmonious and synchronized manner to achieve a larger goal or a more complex operation.  

Now that we know about the core of Kubernetes, we can dive in to get the insights on what exactly is Kubernetes. 

What is Kubernetes: 

Kubernetes is basically an open-source tool developed by Google that offers container orchestration. It aids in the administration of containerized applications across diverse deployment settings.  

Kubernetes has gained significant popularity in the world of containerized applications and microservices because it simplifies the management of complex container deployments, increases scalability and availability, and helps organizations achieve greater operational efficiency. It has now become a fundamental building block for cloud-native and container-based applications. 

Kubernetes helps solve major issues that businesses face with application building, deployment, and management. 

• Container Orchestration: Kubernetes automates the deployment and scaling of containers, ensuring that the right number of containers are running, distributed, and managed efficiently across a cluster. This addresses the need for effective container orchestration.  

• Self-Healing: Kubernetes monitors containers and nodes for failures, and it can automatically restart containers or migrate them to healthy nodes to maintain high availability and resilience. Disaster recovery in case of data loss, server explosion or any such case is made possible with its mechanism to pick up the data and restore it to the latest state, and containerized apps can work from the latest state. 

• Rolling Updates: Kubernetes facilitates rolling updates of containerized applications, allowing new versions to be deployed with minimal downtime.  

• Multi-Cloud and Hybrid Cloud Deployments: Kubernetes is independent of any specific cloud platform and can be implemented on a range of cloud service providers and on-premises infrastructure, alleviating worries about becoming locked into a single vendor and facilitating the adoption of multi-cloud and hybrid cloud approaches. 

• Security: Kubernetes provides inherent security functionalities, such as network policies and secret management, designed to bolster the security of containerized applications. 
• Complexity Management: Kubernetes simplifies much of the intricacy involved in managing containers at a significant scale, offering a more streamlined method for dealing with a substantial volume of containers and services. 

With all this and much more, Kubernetes has eased out the way applications are being run. To understand the overall structure of Kubernetes, we need to understand its basic architecture and components. 

Kubernetes Architecture: 

Kubernetes cluster is made up of at least one master node which is connected to a couple of worker nodes. Each worker node has a process called Kubelet Process running on it, which basically makes it possible for the clusters to communicate and execute relevant tasks. Depending on the workload, the number of containers in each work node varies accordingly.  

The Worker Node is where the actual work takes place. Master node, on the other hand, takes up the important Kubernetes processes that are needed to manage the clusters such as API, User Interface, etc. 

It is to note that if you lose connection with the master node, you cannot access the cluster anymore. Hence, there is a requirement of having another master node. So, there are at least two master nodes in the production environment inside the kubernetes cluster. In any case if one master node fails, there is already another available for backup. 

Kubernetes Components: 

Master Node has the following major components, each serving an important functionality. 

• API server: The Kubernetes API server serves as the central hub for cluster management. It acts as the interface for the Kubernetes control plane, offering a RESTful API that allows users, administrators, and various system components to interact with the cluster. Virtually all administrative tasks and application deployments are orchestrated through API calls to this pivotal component.  

• Controller Manager: It is another process which keeps an overview of what’s happening in the cluster whether something needs to be repaired or if a container dies and needs a restart.  

• Scheduler: It is responsible for scheduling containers on different nodes based on workload. It also decides which work nodes the next container should be scheduled on based on the availability of resources on those worker nodes.  

• etcd: It is a distributed key-value store, which holds the current state of the Kubernetes cluster. It has all the configuration data inside and the status data of each node. This is also responsible for system recovery.  

Important components of Worker Node are: 

• Pods: Pods serve as the smallest deployable units and can house one or more containers. For each application there is one Pod available. Each worker node has multiple pods and inside a Pod there can be multiple containers. Containers located within the same Pod share a common network namespace, making them ideal for services that need to be co-located and tightly integrated.  

• Kubelet: The Kubelet is an essential component running on every worker node in a Kubernetes cluster. It establishes communication with the Kubernetes control plane, which is usually hosted on the master node, and its primary responsibility is to ensure that containers are running within Pods as defined by the desired state of the cluster. 

• Container Runtime: The container runtime plays a crucial role in running the containers within Kubernetes Pods. The container runtime is responsible for fetching container images and running containers in accordance with the specifications defined in the Pod configuration. It essentially executes and manages the lifecycle of containers within the cluster. 

• Node Agent: The Node Agent or Node Controller is tasked with monitoring the overall health of a node within the Kubernetes cluster. Its responsibility includes reporting the node’s status and condition to the control plane especially in the event of node unavailability or failure. 

Another component that turns all the nodes inside of the cluster into one powerful machine is Virtual network. It has the sum of all the resources of individual nodes. Also, it assigns each pod with its own IP address. Pods usually communicate with one another using the assigned IP addresses. 

Also, Pods can die easily, which makes it a need to replace the dead one with a new Pod having a new IP address. But having dynamic IP addresses may be chaotic. This is where the Service comes into play as it has a permanent IP address and is set in front of the Pod. 

Summary: 

Kubernetes is a powerful container orchestration platform that has simplified the deployment and management of containerized applications. Its architecture with specific components that work together create a resilient and efficient containerized environment.  

Kubernetes abstracts away many of the complexities associated with managing containers and allows organizations to build, scale, and maintain modern applications with ease. This technology continues to play a vital role in the world of cloud-native computing and is a cornerstone of many organizations’ IT infrastructures.