Kubernetes Architecture and Components: Explained

Imagine being a tech startup, with a revolutionary solution capable of managing a major issue. Just as you are about to deploy the application, a major bug disrupts its whole credibility. It is definitely not worth the effort, right? In another scenario, you are well aware of the power of containerization and use Kubernetes to you build your application in different containers. Now, even if a bug shows up, or you need to deploy only a part of the application, the process becomes hassle-free with the robust Kubernetes Architecture. Before breaking down the concept of Kubernetes and its architecture, we first need to understand its fundamental concepts- Containerization and Orchestration.

kubernetes

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: 

Google developed Kubernetes, an open-source tool that provides 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. It can automatically restart containers or migrate them to healthy nodes, ensuring high availability and resilience. Its mechanism enables disaster recovery in the event of data loss, server explosion, or similar incidents by picking up and restoring data to the latest state. Containerized apps can then operate seamlessly from this updated state.
  • Rolling Updates: Kubernetes enables the implementation of rolling updates for containerized applications, ensuring minimal downtime during the deployment of new versions. 
  • Multi-Cloud and Hybrid Cloud Deployments: Kubernetes operates independently of any specific cloud platform. This flexibility enables implementation across various cloud service providers and on-premises infrastructure, providing versatility in deployment options. This alleviates concerns about vendor lock-in and facilitates 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 in managing containers at a significant scale. It offers a streamlined method for dealing with a substantial volume of containers and services.

Kubernetes has streamlined the execution of applications, offering various benefits and more. To understand the overall structure of Kubernetes, we need to understand its basic architecture and components. 

kubernetes architecture

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. This process essentially enables communication among clusters and executes relevant tasks efficiently. Depending on the workload, the number of containers in each work node varies accordingly.  

The Worker Node is where the actual work takes place. On the other hand, the master node is responsible for managing crucial Kubernetes processes, including the API and User Interface. This role is essential for the coordination and control of the Kubernetes clusters.

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, providing a RESTful API. This API allows users, administrators, and various system components to interact seamlessly 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 that keeps an overview of what’s happening in the cluster. This includes identifying if something needs repair or if a container dies and requires 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 within the same Pod share a common network namespace. This feature makes 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 communicates with the Kubernetes control plane, typically hosted on the master node, and ensures that containers run within Pods according to 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 monitors 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. The Service comes into play by having a permanent IP address and being 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.

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