Kubernetes Architecture

What is Kubernetes Architecture?

Kubernetes Architecture refers to the components that make up the Kubernetes system. It consists of two main parts: the **Master Node** and **Worker Nodes**. These components work together to ensure efficient deployment, management, and scaling of applications.

Master Node

The **Master Node** is the brain of the Kubernetes cluster. It controls and manages the cluster. The main responsibilities of the Master Node are:

  • API Server: Exposes the Kubernetes API, which is the central point of communication between all components.
  • Scheduler: Decides where to run the workloads (Pods) within the cluster.
  • Controller Manager: Handles the lifecycle of the cluster and ensures the desired state of the system.
  • etcd: Stores all cluster data and configuration in a key-value store.

Worker Nodes

Worker Nodes are where the actual applications (containers) run. Each worker node has the following key components:

  • Kubelet: Ensures that the containers are running in the pods as expected. It communicates with the API server and makes sure that the desired containers are running.
  • Kube-Proxy: Maintains network rules for Pod communication. It handles the networking between Pods and Services.
  • Container Runtime: The software responsible for running containers, e.g., Docker, containerd, or CRI-O.

How the Components Interact

Kubernetes works by allowing the **Master Node** to interact with **Worker Nodes** to deploy and manage applications. Here's a simplified flow of how it works:

  1. The **API Server** receives a request to deploy a new application.
  2. The **Scheduler** decides on the best worker node to deploy the Pod (containerized application).
  3. The **Kubelet** on the worker node starts the container and monitors its health.
  4. If the container crashes, the **Kubelet** will automatically restart it to keep the system healthy.

Communication Between Nodes

The **Master Node** communicates with the **Worker Nodes** through the **API Server**. The worker nodes send status updates back to the master node using **Kubelet** and **Kube-Proxy** to ensure the desired state of the application is always maintained.

Visualizing Kubernetes Architecture

Below is a basic diagram of Kubernetes architecture:


        +----------------+        +---------------------+       +---------------------+
        |    Master      |        |     Worker Node 1   |       |     Worker Node 2   |
        |   Node         | <----> |  Kubelet   Kube-proxy| <--> |  Kubelet   Kube-proxy|
        | (API Server,   |        |  Container Runtime   |       |  Container Runtime  |
        |  Scheduler,    |        |  Pods                |       |  Pods               |
        |  Controller    |        |                      |       |                     |
        |  Manager, etcd)|        +---------------------+       +---------------------+
        +----------------+

Conclusion

Kubernetes architecture ensures that applications are deployed, managed, and scaled in a consistent and reliable way. It abstracts the complexities of managing containerized applications and provides a flexible system to scale workloads easily. Understanding this architecture is key to mastering Kubernetes and using it effectively in production environments.