Kubernetes cluster’s most basic architecture has two major Nodes

1. Master Nodes
2. Worker Nodes or Slave Nodes

Let’s understand first how does worker nodes or slave nodes in K8s works and what are the key component of the worker nodes

As a developer or K8s administrator most of the time you will deal with worker nodes, whether you have to deploy your containerized app or you have to autoscale it, or you have to roll out any new app update on your production-grade server, you will often deal with worker nodes.

Every worker node runs these 3 key processes

1. Container Runtime
2. kubelet
3. kube-proxy

container runtime?

A container runtime, also known as container engine, is a software component that can run containers on a host operating system. Common examples of container runtimes are runC, containerd, Docker, and Windows Containers.

Kubelet?

Kubelet is the technology that applies, creates, updates, and destroys containers on a Kubernetes node.

kubelet is a primary node-agent of the worker node, which interacts with both node and the container in the given worker node.

Within a Kubernetes cluster, the kubelet watches for PodSpecs via the Kubernetes API server.

A PodSpec is a YAML or JSON object that describes a pod. The kubelet takes a set of PodSpecs that are provided through various mechanisms (primarily through the API server) and ensures that the containers described in those PodSpecs are running and healthy.

The Kubelet is the primary and most important controller in Kubernetes. It’s responsible for driving the container execution layer, typically Docker.

Kube-proxy

K8s cluster can have multiple worker nodes and each node has multiple pods running, so if one has to access this pod, they can do so via Kube-proxy.

Master Node in K8s cluster

The master node is also known as a control plane that is responsible to manage worker/slave nodes efficiently. They interact with the worker node to

• Schedule the pods
• Monitor the worker nodes/Pods
• Start/restart the pods
• Manage the new worker nodes joining the cluster

Master Node Processes:

Every master nodes in the K8s cluster runs the following key processes

1. kube-apiserver
2. kubectl: kube-controller-manager
3. kube-scheduler
4. etcd