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Namespace Management

In a Kubernetes cluster, workloads are deployed into a namespace. Multi-cluster deployments mean each namespace must exists in multiple clusters. If you want to manage these namespaces in a unified manner, karmada-controller-manager namespace sync controller is a solution, which propagates namespaces from Karmada to member clusters.

Default namespace propagation​

All namespaces, except those reserved, will be propagated to all member clusters. Reserved namespaces are karmada-system,karmada-cluster, karmada-es-*, kube-* (configured via cli option, see below), and default.

Skip namespace auto propagation​

If you don't want to propagate a namespace automatically:

  • Option A: Configure karmada-controller-manager
  • Option B: Label the namespace
  • Option C: use custom namespace propagation

Option A: Configure karmada-controller-manager​

The flag --skipped-propagating-namespaces can skip namespace auto propagation in karmada-controller-manager which defaults to the regex "kube-.*". Here is an example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: karmada-controller-manager
  namespace: karmada-system
  labels:
    app: karmada-controller-manager
spec:
  ...
  template:
    metadata:
      labels:
        app: karmada-controller-manager
    spec:
      containers:
        - name: karmada-controller-manager
          image: docker.io/karmada/karmada-controller-manager:latest
          command:
            - /bin/karmada-controller-manager
            - --skipped-propagating-namespaces=ns1,ns2

With this change:

  • ns1 and ns2 will not be propagated to all the member clusters.
  • the previously ignored "kube-.*" namespaces will be propagated to all the member clusters.

Option B: Label the namespace​

Configure label namespace.karmada.io/skip-auto-propagation: "true" to skip namespace auto propagation. Here is an example:

apiVersion: v1
kind: Namespace
metadata:
  name: example-ns
  labels:
    namespace.karmada.io/skip-auto-propagation: "true"

Note: If the namespace has been propagated to member clusters, labeling the namespace with namespace.karmada.io/skip-auto-propagation: "true" will not trigger member clusters to delete the namespace, but the namespace will not be propagated to newly joined member clusters.

Option C: use custom namespace propagation.​

If you want to take full control of which namespaces get propagated this option offers the most flexibility, but also means you have to add new clusters to the propagation policy yourself.

Step 1: Disable the namespace-sync-controller (which is called "namespace" internally)​

Change the karmada-controller-manager command to not run the "namespace" controller:

command:
- /bin/karmada-controller-manager
- --controllers=*,-namespace

Step 2: Create a clusterpropagationpolicy to propagate namespaces​

Example:

apiVersion: policy.karmada.io/v1alpha1
kind: ClusterPropagationPolicy
metadata:
  labels:
    role: namespace
  name: namespace
spec:
  conflictResolution: Overwrite
  placement:
    clusterAffinity:
      clusterNames:
      - cluster-a
      - cluster-b
  resourceSelectors:
  - apiVersion: v1
    kind: Namespace
    labelSelector:
      matchExpressions:
      - key: kubernetes.io/metadata.name
        operator: NotIn
        values:
        - kube-system
        - kube-public
        - kube-node-lease
        - default
        - karmada-system
        - karmada-cluster
      - key: karmada.io/managed
        operator: NotIn
        values:
        - "true"