How to understand the Node node of Kubernetes architecture ​

This article shows you how to understand the Kubernetes architecture of the Node node, the content is concise and easy to understand, can definitely brighten your eyes, through the detailed introduction of this article, I hope you can get something.

Node is the place where Pod runs, and Kubernetes supports Docker, rkt and other container Runtime. The Kubernetes components running on Node are kubelet, kube-proxy, and Pod networks (for example, flannel).

Kubelet

Kubelet is the agent of Node. When Scheduler determines that Pod is running on a Node, it will send the specific configuration information of Pod (image, volume, etc.) to the kubelet,kubelet of this node to create and run containers based on this information, and report the running status to Master.

Kube-proxy

Service logically represents multiple Pod at the back end, and the outside world accesses the Pod through service. How are requests received by service forwarded to Pod? This is what kube-proxy is going to do.

Each Node runs the kube-proxy service, which is responsible for forwarding the TCP/UPD data flow that accesses the service to the back-end container. If there are multiple replicas, kube-proxy will achieve load balancing.

Pod network

For Pod to be able to communicate with each other, Kubernetes Cluster must deploy a Pod network, and flannel is one of the options.

A complete architectural diagram

Combined with the experimental environment, we get the following architecture diagram:

The system components of Kubernetes are put into kube-system namespace. Here is a kube-dns component that provides DNS services for Cluster, which we will discuss later. Kube-dns is installed as an add-on when performing kubeadm init (step ⑤).

Kubelet is the only Kubernetes component that does not run as a container, and it runs through Systemd in Ubuntu.

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