Kubernetes Architecture

Control Plane (Master) & Worker Nodes Control Plane components: API Server Scheduler Control Manager etcd Worker Node components: Container Runtime Kubelet Kube-proxy Node Processes Each node has multiple Pods on it. 3 processes must be installed on every node — used to schedule and manage those Pods. Nodes are cluster services that actually do the work. Container Runtime Examples: Docker, containerd, CRI-O. containerd is used in worker nodes — it's lightweight in nature. This should be installed on every node because application Pods need to run containers inside the node. Kubelet The process which schedules the Pods and containers underneath is Kubelet. Kubelet interacts with both the container and the node. Kubelet starts the Pod with the container inside. Communication between two nodes is because of Services. Creation of Pod: Kubelet insures the Pod is always running — if not, it will inform etcd. Kube-proxy Kube-proxy forwards the request from Pod to Service. Makes use of the communication, with load balancing. Provides networking (container ID, IP address). Load balancing — basically using IP tables. It makes sure to send the request to the same machine instead of sending it to others (from same node communications). So, how do you interact with this cluster? Schedule the Pod Monitor Re-schedule/restart the Pod Join a new node Managing processes are done by master nodes (the control plane). API Server When you, as a user, want to deploy a new application in a Kubernetes cluster, you interact with the API server using some client — could be UI or CLI. It's a cluster gateway — it gets the initial request of any update into the cluster, even the queries from the cluster. It also acts as gatekeeper for authentication. It means when you want to schedule new Pods, deploy new applications, create new services, or any other components — you have to talk to it first. Flow: Some request → API server → Validates request → Other processes → Pods Only one entry point to t