Demystifying Kubernetes Architecture: Master & Worker Nodes Explained
This article breaks down the core principles and architecture of Kubernetes, illustrating how master and worker nodes interact, detailing key components such as the API server, scheduler, controllers, kubelet, kube-proxy, and container runtimes, and explains deployment scenarios on major cloud providers.
In this article we explain the principles and architecture of Kubernetes, illustrating how applications are hosted on servers and how the platform organizes them into master and worker nodes.
When Kubernetes is not installed, applications run directly on the host machines. When it is installed, the cluster is divided into a master node that controls the cluster and multiple worker nodes that run the actual workloads.
Figure 1 shows the separation between applications and servers.
Figure 2 illustrates the master node and worker nodes in a Kubernetes cluster.
Master Node
Interaction via the kubectl CLI or UI tools.
The API server exposes the Kubernetes API, handling authentication, authorization, and receiving user requests such as creating pods.
The API server stores cluster state in etcd, enabling coordination of configuration, deployment, service discovery, load balancing, job scheduling, and health monitoring.
The scheduler watches for unscheduled pods and assigns them to suitable nodes based on resource availability.
Controllers monitor the health of cluster objects, with specific controllers for nodes, jobs, endpoints, service accounts, and tokens.
Worker Node
The kubelet runs on each node, ensuring containers run inside pods.
Kube‑proxy maintains network rules on the node, allowing pods to communicate across nodes.
The container runtime executes containers; Kubernetes supports Docker, CRI‑O, containerd, and others.
Figure 5 demonstrates how pods on different nodes communicate via kube‑proxy network rules.
When using a managed Kubernetes service from cloud providers such as Azure, Alibaba Cloud, or Tencent Cloud, the master node is managed by the provider, and users only need to manage the worker nodes.
Summary
This overview provides a clear understanding of Kubernetes architecture and its main components.
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