What is Kubernetes and What Are Its Features?

What is Kubernetes?

In today's IT world, containers are widely used as a popular method for packaging and deploying software in different environments. As the number of containers increases, managing them becomes challenging, and this is where Kubernetes comes into play. Kubernetes is an open-source, scalable, and portable platform used for managing and orchestrating containers. It automates container management, eliminating the need for manual handling of containers.

Kubernetes History

Before introducing Kubernetes, Google used its internal system called Borg to manage containers. This system helped Google manage its massive workloads across data centers. Using this experience, Google concluded that such a tool could also be beneficial for the open-source community.

In August 2014, Google released the first version of Kubernetes, which was met with significant enthusiasm from developers. Between 2016 and 2018, with continuous updates and advancements, Kubernetes quickly became one of the most popular container orchestration tools, with large companies like IBM, Microsoft, and AWS starting to integrate it into their services.

Today, Kubernetes is one of the leading platforms for managing container workloads in both cloud and on-premises environments. It is continuously updated and has gained a large audience in the developer community.

Kubernetes Architecture

The architecture of Kubernetes revolves around clusters, which are made up of various components that work together.

What is a Cluster?

A cluster consists of multiple servers or nodes, which are divided into two types:

1. Control Plane: This includes the central components of Kubernetes that manage and control the cluster. It consists of the Controller Manager, Scheduler, API Server, and the etcd database server.
2. Worker Node: Each cluster typically has one or more worker nodes. These are physical or virtual servers where applications are run in the form of Pods. Pods are the smallest executable units in Kubernetes and consist of one or more containers.

Let's continue with more detailed explanations of each component:

• Controller Manager: The Controller Manager observes the desired and current state of the resources it manages in the cluster through the API Server. If the desired and current states do not match, it takes corrective actions to steer the resources towards the desired state.
• API Server: The API Server is the entry point in the Kubernetes Control Plane. This server is aware of updates, scaling, and other lifecycle management operations of cluster resources. It serves as the communication interface for all other subservices. Acting as a gateway, it allows clients to access cluster resources from outside the cluster, and it facilitates authentication for accessing the required resources within the cluster. Clients use the API Server as a tunnel to communicate with nodes, services, and pods.
• Scheduler: The Scheduler's job is to calculate resource utilization for each node and decide whether new pods should be deployed. If new pods are required, the scheduler determines which node is the most suitable for their deployment. Overall, the Scheduler helps optimize resource consumption and ensures that applications run with the best possible performance.
• ETCD Database: ETCD is a high-performance, scalable key-value database. It stores data related to configurations and the current state of the cluster. ETCD plays a vital role in Kubernetes, as all components of the cluster rely on its data for proper functioning and synchronization.
• Nodes: A Kubernetes cluster must have at least one computational node. Pods are coordinated and scheduled to run on these nodes. Nodes perform tasks such as connecting applications, networking, and linking computational and storage resources. Nodes can be either virtual machines or physical servers.
• CRI (Container Runtime Interface): CRI is a standard interface that allows Kubernetes to interact with different container runtimes. It is specifically designed to separate the container-related components from other parts of Kubernetes.
• Kubelet: Each computational node includes a Kubelet. The Kubelet is an agent that communicates with the control plane and ensures that pods are running as instructed. It monitors pods to ensure they are in the desired state.
• Kube-proxy: Every computational node has a Kube-proxy, which facilitates network services in Kubernetes. This proxy can route traffic directly or use the operating system's filtering capabilities to manage network communication inside and outside the cluster. It runs on each node to ensure that services are accessible to external resources and are connected to a separate host subnet.
• Pods: Pods are critically important in Kubernetes as they are the structures that developers interact with directly. Pods are the smallest and simplest deployable units in Kubernetes and represent one or more containers that share resources and network configurations. Pods are the main management unit in the Kubernetes ecosystem, acting as logical boundaries for containers that share resources and context.

Features of Kubernetes

Kubernetes becomes essential when there are a large number of containerized applications. It helps developers and system administrators run containerized apps automatically with high reliability. The features of Kubernetes have made it one of the most popular orchestration tools globally. Some of these features are described below:

• Auto-Scaling: Kubernetes can increase or decrease the number of pods based on workload demands. This feature ensures that applications always run with sufficient resources.
• Load Balancing: Kubernetes distributes incoming traffic among different pods to ensure the workload is evenly distributed across them.
• Self-Healing: Kubernetes automatically rebuilds pods that have failed or crashed, and it removes any nodes that are out of service, redistributing the load to healthy nodes.
• Rollout: This feature allows applications to be updated gradually and in a controlled manner. If an issue arises, it can quickly roll back to the previous version.
• Persistent Storage: This feature is essential for applications that need to store data long-term. It provides storage space that retains data even after pods are shut down or moved.
• Deployment: Deployment is primarily used to manage the lifecycle of applications. It is a Kubernetes resource that allows users to deploy, update, scale, and manage pods.
• Hybrid and Multi-Cloud Support: This important feature allows developers to run and manage applications and services across different environments seamlessly.

Docker vs Kubernetes

Docker is a tool for building application images and running them as containers. It is essentially a container runtime with some features like image creation, deployment management, etc., but it has limited capabilities. Docker provides a limited ability to manage container deployments within a small cluster using Docker Swarm. However, it doesn't perform well in larger clusters.

Kubernetes, on the other hand, is a tool designed for deploying containers in clusters ranging from small to large. Kubernetes uses a container runtime like Docker or Containerd for container execution. It comes with features like services, ingress, secrets, load balancing, and more. With Kubernetes, users benefit from features like pods, deployments, scalability, and distribution.

Kubernetes Monitoring

The Moein monitoring platform offers the capability to monitor the health of the Kubernetes cluster, its nodes, pods, namespaces, and deployments. To see the list of available Kubernetes metrics for monitoring on the Moein platform, click here.