Chapter Seven
Extending Kubernetes
Turning Kubernetes into a platform — Custom Resource Definitions, the operator and controller pattern that automates operations, and the other ways to extend the API.
The same reconcile loop that manages Pods can manage anything. That is the insight behind extending Kubernetes: teach the API new object kinds and write controllers that drive them to desired state.
This chapter covers Custom Resource Definitions that add your own resources, the operator pattern that packages a controller with the knowledge to run a stateful system, and the other extension points — aggregated API servers, admission and authorization webhooks — that turn the cluster into a platform.
Topics in This Chapter
Topic 38
Custom Resource Definitions
Adding your own object kinds to the API with schema and validation. The foundation every operator builds on.
Topic 39
Operators and Controllers
Encoding operational knowledge as a controller that reconciles a custom resource. How operators run databases and complex systems for you.
Topic 40
Extending the API
Beyond CRDs — aggregated API servers, admission and authorization webhooks, and the trade-offs of each extension mechanism.