Responsible for a resource type
Waits for events for this kind
Converges the state toward the description
Builtin resource types, e.g. Pod
Custom resources to extend Kubernetes
Many controllers ship with a custom resource type
Custom resource are described in a Custom Resource Definition (CRD)
Can have validation since 1.16
Accepted without validation only before 1.22
apiextensions.k8s.io/v1beta1 was deprecated and…
…is superceded by apiextensions.k8s.io/v1
Controllers must ship updated CRDs
API deprecations are documented
Quick and dirty
Written in bash (yes, that is possible)
CRD for controlling replicas
apiVersion: k8s.dille.io/v1
kind: ReplicaConfig
metadata:
name: nginx
spec:
kind: Deployment
name: nginx
replicas: 3
Controllers can control the state of external services
Custom resource describes that desired state
Controller synchronized this state
The external service is updated when the custom resource is…
…created
…modified
…removed
Enables infrastructure management from Kubernetes