/k8s-demo

demo usage of k8s

Kubernetes Demo

The purpose of this repo is to provide a jumping-off point for cool kubernetes projects.

Definitions

Let's check out some terminology below.

Basic Objects

  • pod -> container / set of containers + storage resources + unique IP + local options
  • service -> abstraction layer on top of a set of ephemeral pods (think of this as the 'face' of a set of pods)
  • volume -> sometimes-shared, persistent storage
  • namespace -> virtual cluster on top of an underlying physical cluster

Service Types

  • clusterIP -> exposes services only inside the cluster (default)
  • nodePort -> exposes services at the specified port on all nodes (<node-ip>:<nodePort>)
  • loadBalancer -> exposes the service with a cloud-provider's load balancer.
  • externalName -> this maps a service to endpoints completely outside of the cluster

Controllers

  • replicaSet -> ensures a certain number of pods are running
  • deployment -> declaritively manages a replicaSet
  • statefulSet -> like a deployment, but for non-interchangeable (or stateful) underlying pods
  • daemonSet -> manages pods that need to run on all/some nodes
  • job -> manages a set of pods that run to completion and tracks the overall progress

Control Plane

  • master -> entity responsible for managing cluster state
    • kube-apiserver -> exposes cluster control and state
    • kube-controller-manager -> this is where the 'brain' of controllers live
    • kube-scheduler -> matches resources to work
  • node -> individual machine/vm that make up the cluster
    • kubelet -> service that communicates with the master
    • kube-proxy -> proxy for connecting to the cluster network

Resources