apricotes notes

kubebuilder/content.md

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+# Kubebuilder
+
+---
+
+### Content
+
+- CRDs
+- Controller / Operator
+- Kubebuilder
+- Live Coding
+- Real Life Use Cases
+
+---
+
+## CRDs
+
+---
+
+## Controller
+
+> A **control loop** that watches the state [...] and makes changes attempting to move the **current state towards the desired state**.
+
+- [Kubernetes Glossary](https://kubernetes.io/docs/reference/glossary/?fundamental=true#term-controller)
+
+--
+
+## Controller
+
+- integrated in `kube-apiserver` or `kube-controller-manager`
+- watch builtin k8s objects (`core`, `apps`, `batch`)
+- logic ontop of data
+- create sub-resources
+
+--
+
+## Controller
+
+### deployment controller
+
+- watches `Deployments`
+- creates and deletes `ReplicaSets`
+- scales `ReplicaSets` for rolling deployments
+
+--
+
+## Controller
+
+### kubelet
+
+- watches `PodSpecs`
+- starts/stops containers
+
+--
+
+## Operator
+
+- term coined by CoreOS
+- same as controller but for CRDs
+- integrate operational knowledge
+- provide usability features
+  - updates
+  - scaling
+  - backups
+  - integration with k8s
+
+---
+
+## Kubebuilder
+
+---
+
+## Live Coding
+
+Check out the source at  
+https://github.com/apricote/kubebuilder-poke-sync
+
+---
+
+## Real Life Use Cases
+
+### Databases
+
+- scaling
+- configuration
+- disaster recovery
+- e.g. [zalando/postgres-operator](https://github.com/zalando/postgres-operator)
+- e.g. [mongodb-enterprise-kubernetes](https://github.com/mongodb/mongodb-enterprise-kubernetes)
+
+--
+
+## Real Life Use Cases
+
+### Provisioning external resources
+
+- call external APIs
+- expose external state in cluster
+- e.g. [jetstack/cert-manager](https://github.com/jetstack/cert-manager)
+- e.g. [awslabs/aws-service-operator](https://github.com/awslabs/aws-service-operator)
+
+--
+
+## Real Life Use Cases
+
+### Application Lifecycle Managment
+
+- deployment
+- supervised updates
+- health checking + alerts
+- Helm Chart++
+- e.g. [gitlab-operator](https://gitlab.com/charts/components/gitlab-operator)
+- e.g. [Tenant Operator](https://blog.kolide.com/using-a-kubernetes-operator-to-manage-tenancy-in-a-b2b-saas-app-250f1c9416ce)