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README.md

Kubernetes Features

Namespaces

Kubernetes supports multiple virtual clusters backed by the same physical cluster. These virtual clusters are called namespaces.

When to use multiple namespaces seems to be arguable.

  • Kubernetes - Namespaces
    • For clusters with a few to tens of users, you should not need to create or think about namespaces at all. (in the Kubernetes document.)
  • RedHat - Kubernetes Namespaces Demystified - How To Make The Most of Them
    • Do not overload namespaces with multiple workloads that perform unrelated tasks.
    • Users should create namespaces for a specific application or microservice and all of the application requirements. Reasons:
      • Simplified recreation of the entire application
      • Fine-grained network management
      • Greater scalability
      • Greater observability
  • Google Cloud - Kubernetes best practices: Organizing with Namespaces
    • Small team: 5~10 microservices → default Namespace
    • Rapidly growing teams: 10+ microservices → each team owns their own microservices -> Use multiple clusters or namespaces for production and development or Each team may choose to have their own namespace
    • Large: not everyone knows everyone else. → each team definitely needs its own namespace. Each team might even opt for multiple namespaces to run its development and production environments.

Admission Controllers

An admission controller is a piece of code that intercepts requests to the Kubernetes API server prior to persistence of the object, but after the request is authenticated and authorized.

Admission controllers may be "validating", "mutating", or both.

You can turn on each of them by the argument --enable-admission-plugins of api-server.

kube-apiserver --enable-admission-plugins=NamespaceLifecycle,LimitRanger ...

Admission controllers list:

  1. DefaultStorageClass: Set default storage class for PersistentVolumeClaim
  2. AlwaysPullIMages: Set imagePullPolicy to Always
  3. MutatingAdmissionWebhook (dynamic admission control): execute mutating admission control webhook
  4. ValidatingAdmissionWebhook (dynamic admission control): execute validating admission control webhook
  5. and more...

Owner References

Owner References

Garbage Collection

If you want to know about garbage collection, please read Garbage Collection.