leopoldodonnell / demo-kubernetes-controller

A demo Kubernetes controller written in go

Demo Kubernetes Controller

The Demo Kubernetes Controller is a Kubernetes controller that provides an example of a Kubernetes client, writtin in go, that can be run from the command line, or from within a cluster to respond to changes in Nodes, Namespaces and Services.

• when namespaces change, demo-controller will update its subscription to services in that namespace
• when services change, demo-controller will announce the change and perform and necessary bookkeeping
• when nodes change, ingress-mapper will nnounce the change and perform and necessary bookkeeping

Usage

Application Notes

General

The application is written in go and built using the client-go framework. It may either be run outside of a cluster as a stand-alone application, or within a cluster in a container. The application uses the (flag)[https://golang.org/pkg/flag/] package for handling command-line arguments and uses the golang glog logging package that enables multiple levels of logging: Info, Warning, Error, and Fatal. The application is multi-threaded, so care is taken to ensure that updates to datastructures.

Program Flow

The general flow of the program is as follows.

Initialize the configuation from the command line
Create An Instance of a DemoController
  Get existing Nodes
  Get existing Namespaces
  Create a kubernetes controller for Nodes
  Create a kubernetes controller for Namespaces
  Create a kubernetes controller Services per each Namespace
Run all of the controllers, each in its own thread and wait for the application to exit

All of the heavy-lifting is done by performing bookkeeping from controller AddFunc, DeleteFunc and UpdateFunc functions, then calling out to an external script that is customized to affect the appropriate changes in an external load-balancer.