Kubernetes Architecture

what is Kubernetes?

Kubernetes is a system for managing containerized applications across a cluster of nodes. In simple terms, you have a group of machines and containerized applications (e.g. Dockerized applications), and Kubernetes will help you to easily manage those apps across those machines. It is used as an alternative for the docker swarm.

Kubernetes Architecture

Kubernetes follows a client-server architecture. The master server consists of various components including a kube-apiserver, an etcd storage, a kube-controller-manager, a cloud-controller-manager, a kube-scheduler, and a DNS server for Kubernetes services.

Kubernetes Architecture

Master

The master node is the most vital component of Kubernetes architecture. It is the entry point of all administrative tasks. There is always one node to check for fault tolerance.

The master node has various components, such as:

1. ETCD
2. Controller Manager
3. Scheduler
4. API Server
5. Kubectl

1. ETCD

This component stores the configuration details and essential values. It communicates with all other components to receive the commands to perform an action. Manages network rules and post-forwarding activity

2. Controller Manager

• A daemon (server) that runs in a continuous loop and is responsible for gathering information and sending it to the API Server. Works to get the shared set of clusters and change them to the desired state of the server
• The key controllers are the replication controllers, endpoint controller, namespace controllers, and service account controllers
• The controller manager runs controllers to administer nodes and endpoints

3. Scheduler

• The scheduler assigns the tasks to the slave nodes
• It is responsible for distributing the workload and stores resource usage information on every node
• Tracks how the working load is used on clusters and places the workload on available resources.

4. API Server

• Kubernetes uses the API server to perform all operations on the cluster
• It is a central management entity that receives all REST requests for modifications, serving as a frontend to the cluster
• Implements an interface, which enables different tools and libraries to communicate effectively

5. Kubectl

• Kubectl controls the Kubernetes cluster manager

Syntax — kubectl [flags]

Slave

The slave node has the following components:

1. Pod

A pod is one or more containers controlled as a single application. It encapsulates application containers, storage resources, and is tagged by a unique network ID and other configurations that regulate the operation of containers

2. Docker

• One of the basic requirements of nodes is Docker
• It helps run the applications in an isolated, but the lightweight operating environment. It runs the configured pods
• It is responsible for pulling down and running containers from Docker images

3. Kubelet

• Service responsible for conveying information to and from the control plane service
• It gets the configuration of a pod from the API server and ensures that the containers are working efficiently
• The kubelet process is responsible for maintaining the work status and the node server

4. Kubernetes Proxy

• Acts as a load balancer and network proxy to perform service on a single worker node
• Manages pods on nodes, volumes, secrets, the creation of new containers, health check-ups, etc.
• A proxy service that runs on every node that makes services available to the external host

That’s it. Hope you found the article useful and thank you for reading it.