Understanding Kubernetes Architecture — A Beginner’s Guide

Unveiling the Blueprint: Navigating the Inner Workings of Kubernetes

Find Complete mind map of A Beginner’s Guide to Kubernetes

In this post, we will again discuss the key components of the Kubernetes system architecture, as highlighted in the diagram from the Kubernetes documentation.

Check out “Understanding Kubernetes — A Beginner’s Guide” for the comprehensive series🚀

A deployment of Kubernetes is called a “Cluster.”

On the left side of the diagram is the control plane, which is responsible for making decisions about the cluster and detecting and responding to events within the cluster.

The control plane consists of several components, including the Kubernetes API server, etcd, the Kubernetes scheduler, the Kubernetes controller manager, and the cloud controller manager.

Control Plane

The control plane is the brain of a Kubernetes cluster. It makes decisions about the cluster and detects and responds to events in the cluster. The main components of the control plane are:

Kubernetes API server

The Kubernetes API server is the entry point for all communication in the cluster. It exposes the Kubernetes API, which accepts commands to view or change the state of the cluster.

etcd

Etcd is a highly available key-value store that contains all the cluster data. When you tell Kubernetes to deploy your application, that deployment configuration is stored in etcd. Etcd is the source of truth for the state in a Kubernetes cluster, and the system works to bring the cluster state into line with what is stored in etcd.

Kubernetes scheduler

The Kubernetes scheduler assigns newly created Pods to nodes. The scheduler determines where your workloads should run within the cluster.

Kubernetes controller manager

The Kubernetes controller manager runs all the controller processes that monitor the cluster state and ensure that the actual state of a cluster matches the desired state.

Cloud controller manager

The cloud controller manager runs controllers that interact with the underlying cloud providers. These controllers effectively link clusters into a cloud provider’s API.

Let’s now zoom in on the right side to learn more about the worker nodes.

Worker Nodes

Nodes are the worker machines in a Kubernetes cluster. User applications are run on nodes. Nodes can be virtual or physical machines. Each node is managed by the control plane and is able to run Pods.

Nodes are not created by Kubernetes itself, but rather by the cloud provider. This enables Kubernetes to run on a variety of infrastructures. The nodes are then managed by the control plane. The components on a node enable that node to run Pods:

kubelet

This is the most important component. This controller communicates with the Kubernetes API server to receive new and modified Pod specifications and ensures that those Pods and their associated containers are running as desired. The kubelet also reports to the control plane on health and status.

Container runtime

In order to start a Pod, the kubelet uses the container runtime, which is responsible for downloading images and running containers. Kubernetes implements a Container Runtime Interface that permits pluggability of the container runtime. While Docker is likely the best-known runtime, rkt and CRI-O are two other commonly used container runtimes.

Kubernetes proxy

This is a network proxy that runs on each node in a cluster. This proxy maintains network rules that allow communication to Pods running on nodes — in other words, communication to workloads running on your cluster. This communication can come from within or outside of the cluster.

Key Takeaways

Let’s recap!

we explored the architecture of a Kubernetes cluster, uncovering important concepts that every beginner should know.

Here are the key takeaways:

1. Control Plane: The control plane is the decision-making center of the cluster, consisting of various components responsible for managing and orchestrating the cluster’s operations.

2. Node Architecture: Kubernetes utilizes separate nodes to host essential components and user workloads. These nodes work together to form a robust and scalable cluster.

3. Controllers: Controllers play a crucial role in maintaining the desired state of the cluster. They continuously monitor and reconcile the actual state with the desired state, ensuring that applications run smoothly.

By understanding the architecture of a Kubernetes cluster, you are equipped with the foundational knowledge necessary to navigate the Kubernetes ecosystem.

Stay tuned for more informative content in our Understanding Kubernetes — A Beginner’s Guide, where we delve deeper into the core concepts and features of Kubernetes.

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