Custom Controllers

• Follows on from the flighttickets.
• A Controller is a any process or loop that continually monitors the ETCD cluster and listens for events of any objects being changed - for example the flight ticket object.
• Can write a Custom Controller in Python - can watch for changes or calls to the Flightticket API
• Developing in Go allows for the use of the Kubernetes Go client - shared informers.
• https://github.com/kubernetes/sample-controller
• To create a sample controller:
  • Set up GoLang
  • Clone the Sample Controller.
  • Change into the sample-controller directory.
  • Customise the Controller with your own logic.
    • For example add code to poll flight booking API to book the tickets.
  • Then build the program with go build -o sample-controller .
  • ./sample-controller -kubeconfig=$HOME/.kube/config
• How to distribute the Controller? Can package the Controller inside a Docker image and run the Controller inside the pod.
• Maybe questions in the exam to build custom resource definition files.