Kubernetes

This is a work in progress and as usual, until it is finished, it will hang out here in the ongoing area.

So what is Kubernetes?

An open source container orchestration system
Runs docker (or rkt) containers
Supports multiple clouds and bare metal deployments
Manages applications, not machines
Automatic placement of containers (like VMWare DRS)

So what are the concepts in Kubernetes?

Containers run on clusters
Pods are a group of containers that work together.
Services are pods that work together
Labels are names that are used to organise services

Replication controllers

Ensures that a specific number of copies of a given pod are running at any one time
Creates or kills pods as required to obtain the desired state

Containers

Make your app portable
It looks the same everywhere, no matter where you run it
Doesn’t need you to install all the app dependencies on your host

Pods

A pod is a group of one or more containers
Each pod gets an IP address
An entire pod sits on a single node

The Atomic unit of scheduling for different types of virtualisation

Hypervisor -> VM (Virtual Machine)
Docker -> Container
Kubernetes -> Pod

Using the Pets vs Cattle analogy

VM are Pets, if they start to go wrong, you fix them
Pod are cattle, if they go wrong, you kill them, they die and another takes its place

Services

Services allow pod to talk to each other and talk to the “outside world”
Are “REST” objects in the k8s API
Give a stable IP endpoint#

Service Types

ClusterIP -> Exposes an app inside the cluster and gives it a stable IP
NodePort -> Exposes the app outside of the cluster by adding a cluster-wise port on top of ClusterIP
LoadBalancer -> Integrated NodePort with cloud-based loadbalancers

Deployments

tbc