Karmada operator

Overview

The Karmada operator is a method for installing, upgrading, and deleting Karmada instances. It builds upon the basic Karmada resource and controller concepts, provides convenience to centrally manage entire lifecyle of Karmada instances in a global cluster. With the operator, you can extend Karmada with custom resources (CRs) to manage your instances not only in local clusters but also in remote clusters.

This document is an overview of how the operator works from a user perspective.

Developer quick start

This section describes how to install karmada-operator and create a Karmada instance with CR.

Prerequisites

• Kubernetes 1.16+
• Helm v3+

Deploy karmada-operator

Helm install

Go to the root directory of the karmada-io/karmada repo. To install the Helm Chart with the release name karmada-operator in the namespace karmada-system, simply run the helm command:

helm install karmada-operator -n karmada-system  --create-namespace ./charts/karmada-operator --debug

Using YAML resource

The karmada-operator workload requires a kubeconfig of the local cluster to establish a connection with the cluster and watch CR resources. In preparation for this, create a secret containing the kubeconfig for the karmada-operator.

kubectl create namespace karmada-system
kubectl create secret generic my-kubeconfig --from-file=$HOME/.kube/config -n karmada-system

Deploy the karmada-operator workload.

kubectl apply -f operator/config/deploy/karmada-operator.yaml

The pod of karmada-operator in the karmada-system namespace will be running.

kubectl get po -n karmada-system

NAME                               READY   STATUS    RESTARTS   AGE
karmada-operator-5b7f485c5-g5lj5   1/1     Running   0          26s

Create a Karmada instance

The Karmada operator provides a Karama CR that can define most configurations for Karmada components. It includes image messages, replica, the args of binary file, and custom label, annotation, and featuregate. For details, see API.

A Karmada CR represents a Karmada instance, which is a namespace-scoped resource. The example below is to create a simple Karmada CR in the test namespace:

kubectl create namespace test
kubectl apply -f - <<EOF
apiVersion: operator.karmada.io/v1alpha1
kind: Karmada
metadata:
  name: karmada-demo
  namespace: test
EOF

Wait for around 40 seconds, and the pods of the Karmada components will be running in the same namespace as the Karmada CR.

kubectl get po -n test
karmada-demo-aggregated-apiserver-587bc5c697-v27vb      1/1     Running   0          12s
karmada-demo-apiserver-55968d9f8c-mp8hf                 1/1     Running   0          35s
karmada-demo-controller-manager-64455f7fd4-stls6        1/1     Running   0          5s
karmada-demo-etcd-0                                     1/1     Running   0          37s
karmada-demo-kube-controller-manager-584f978bbd-fftwq   1/1     Running   0          5s
karmada-demo-scheduler-6d77b7547-hgz8n                  1/1     Running   0          5s
karmada-demo-webhook-6f5944f5d8-bpkqz                   1/1     Running   0          5s

Tip:

If no spec.hostCluster.secretRef is specified in CR, the Karmada instance will be installed in the cluster where karmada-operator is located.

Upgrade a Karmada instance

Once a Karmada instance is created, the CR resource is automatically filled with default values. To upgrade the Karmada instance, for example, you can upgrade the Karmada version to v1.5.0 or higher:

kubectl patch karmada karmada-demo -n test --type merge -p '
{
  "spec": {
    "components": {
      "karmadaAggregatedAPIServer": {
        "imageTag": "v1.5.0"
      },
      "karmadaControllerManager": {
        "imageTag": "v1.5.0"
      },
      "karmadaScheduler": {
        "imageTag": "v1.5.0"
      },
      "karmadaWebhook": {
        "imageTag": "v1.5.0"
      }
    }
  }
}'

Delete a Karmada instance

Deleting a Karmada CR is a delicate operation that requires careful attention. Once the Karmada CR is deleted, the associated Karmada instance will also be deleted. It is important to proceed with caution when deleting a Karmada CR due to the potential risks involved.

kubectl delete karmada karmada-demo -n test

Custom Karmada CR

This feature allows you to configure the Karmada CR to install Karmada instances flexibly. For details, see karmada.yaml.

Set Karmada component replicas

The replicas of all Karmada components can be modified. For example, you can scale the etcd pod replicas to 3:

apiVersion: operator.karmada.io/v1alpha1
kind: Karmada
metadata:
  name: karmada-demo
  namespace: test
spec:
  components:
    etcd:
      local:
        replicas: 3

Custom label and annotation

All Karmada components allow for custom labels and annotations to be set. These are merged into both pod and workload resources.

apiVersion: operator.karmada.io/v1alpha1
kind: Karmada
metadata:
  name: karmada-demo
  namespace: test
spec:
  components:
    karmadaAPIServer:
      labels: 
        <custom-label-key>: <custom-label-value>
      annotations:
        <custom-annotation-key>: <custom-annotation-value>

Change karmada-apiserver service type

The service type of karmada-apiserver is ClusterIP by default. You can change it to NodePort:

...
karmadaAPIServer:
  imageRepository: registry.k8s.io/kube-apiserver
  imageTag: v1.25.4
  replicas: 1
  serviceType: NodePort
  serviceSubnet: 10.96.0.0/12
...

Add karmada-apiserver SANs

You can add more SANs to karmada-apiserver certificate:

...
karmadaAPIServer:
  imageRepository: registry.k8s.io/kube-apiserver
  imageTag: v1.25.4
  replicas: 1
  serviceSubnet: 10.96.0.0/12
  certSANs:
  - "kubernetes.default.svc"
  - "127.0.0.1"
...

Install karmada addon

By default, the Karmada operator does not install the descheduler and search addons. If you want to use them, you should add definitions to the Karmada CR. Here is an example of the descheduler addon:

apiVersion: operator.karmada.io/v1alpha1
kind: Karmada
metadata:
  name: karmada-demo
  namespace: test
spec:
  components:
    KarmadaDescheduler: {}

If you want to install with the defaults, simply define an empty struct for descheduler.

Tip:

Now, we only support installing the descheduler addon.

Contributing

The karmada/operator repo is part of Karmada from 1.5 onwards. If you're interested in the Karmada operator and want to contribute your code and ideas, welcome to open PRs and issues. See CONTRIBUTING for details on submitting patches and the contribution workflow.