[Container] Kubernetes Architecture

• Idenetify the components of a Kubernetes architecture
• Identify the components of a control plane
• Identify the components of a worker plane

 Kube-api-server: 

• Exposes the kubernetes API
• Front-end for the kubernetes control plane
• All communication in the cluster utilizes this API
• Designed to scale horizontally and balance traffic between them

kube-controller-manager

• Runs controller processes that monitor cluster state
• Runs controller processes that ensure the actual state matches the desired state

cloud-controller-manager

• Runs controllers that interact with underlying cloud providers
• Links clusters into a cloud provider's API

etcd

• Highly available, distributed key-value store that contains all cluster data
• Stores deployment configuration data, the desired state, and meta can be accessed in a common location

kube-scheduler

• Assigns newly created Pods to nodes
• Selects optimal node according to Kubernetes scheduling principles, configuration options, and available resources

 Nodes

• Are the worker machines in Kubernetes
• May be a virtual or physical machine
• Managed by the control plane
• Contain the services necessary to run applications
• Nodes include pods which are the smallest deployment entity in Kubernetes

Kubelet

• Communicates with the API server
• Ensure that Pods and their associated containers are running
• Reports to the control plane on the pods' health and status

Container runtime

• Downloads images and runs containers
• Kubernetes implements an interface so that this component is pluggable
• Docker is a well-know runtime

Kubernetes proxy

• Network proxy
• Maintains network rules that allow communication to Pods