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2.1: Technology Overview

Technology Overview

Planes and Nodes

The first concepts to understand with regard to kubernetes are:

  • Node: A "node" is a computer/server. Multiple nodes are joined together to form a "cluster".
  • Control Plane: A subset of nodes in the cluster dedicated to performing system tasks. Nodes that are part of the control plane are referred to as "control plane nodes".
  • Data Plane: A subset of nodes in the cluster dedicated to running user worklods. Nodes that are part of the data plane are referred to as "worker nodes".
Diagram showing a Kubernetes cluster and its nodes

Kubernetes System Components

Kubernetes is comprised of many smaller components:

  • etcd: Key-value store used for storing all cluster data. It serves as the source of truth for the cluster state and configuration.

  • kube-apiserver: The front end for the Kubernetes control plane.

  • kube-scheduler: Schedules pods onto the appropriate nodes based on resource availability and other constraints.

  • kube-controller-manager: Runs controller processes. Each controller is a separate process that manages routine tasks such as maintaining the desired state of resources, managing replication, handling node operations, etc...

  • cloud-controller-manager: Integrates with the underlying cloud provider (if running in one) to manage cloud-specific resources. It handles tasks such as managing load balancers, storage, and networking.

  • kubelet: An agent that runs on each worker node and ensures that containers are running in pods and manages the lifecycle of containers.

  • kube-proxy: This network proxy runs on each node and maintains network rules to allow communication to and from pods.

Diagram showing Kubernetes system components