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karmada/examples/customresourceinterpreter/README.md

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# Resource Interpreter Webhook
This document uses an example of a resource interpreter webhook to show users its usage. In the example, we process a CustomResourceDefinition(CRD) resource named `Workload`. Users can implement their own resource interpreter webhook component based on their own business, taking `karmada-interpreter-webhook-example` as an example.
## Document introduction
```
examples/customresourceinterpreter/
│
├── apis/ # API Definition
│ ├── workload/ # `Workload` API Definition
│ │ ├── v1alpha1 # `Workload` v1alpha1 version API Definition
│ │ | ├── doc.go # API Package Introduction
│ │ | ├── workload_types.go # example `Workload` API Definition
│ │ | ├── zz_generated.deepcopy.go # generated by `deepcopy-gen`
| | | └── zz_generated.register.go # generated by `register-gen`
│ └── └── workload.example.io_workloads.yaml # `Workload` CustomResourceDefinition, generated by `controller-gen crd`
│
├── webhook/ # demo for `karmada-interpreter-webhook-example` component
│
├── karmada-interpreter-webhook-example.yaml # component deployment configuration file
├── README.md # README file
├── webhook-configuration.yaml # ResourceInterpreterWebhookConfiguration configuration file
├── workload.yaml # `Workload` resource example
└── workload-propagationpolicy.yaml # `PropagationPolicy` resource example to propagate `Workload` resource
```
## Install
For a Karmada instance, the cluster where the Karmada component is deployed is called `karmada-host` cluster.
This document uses the Karmada instance installed in `hack/local-up-karmada.sh` mode as an example, there are `karmada-host`, `karmada-apiserver` and three member clusters named `member1`, `member2` and `member3`.
> Note: If you use other installation methods, please adapt your installation method proactively.
### Prerequisites
Considering that there is a `Pull` type cluster in the cluster, it is necessary to set up a LoadBalancer type Service for `karmada-interpreter-webhook-example` so that all clusters can access the resource interpreter webhook service. In this document, we deploy `MetalLB` to expose the webhook service.
If all your clusters are `Push` type clusters, you can access the webhook service in the `karmada-host` cluster through `Service` without configuring additional `MetalLB`.
Please run the following script to deploy `MetalLB`.
```bash
kubectl --context="karmada-host" get configmap kube-proxy -n kube-system -o yaml | \
sed -e "s/strictARP: false/strictARP: true/" | \
kubectl --context="karmada-host" apply -n kube-system -f -
curl https://raw.githubusercontent.com/metallb/metallb/v0.13.5/config/manifests/metallb-native.yaml -k | \
sed '0,/args:/s//args:\n - --webhook-mode=disabled/' | \
sed '/apiVersion: admissionregistration/,$d' | \
kubectl --context="karmada-host" apply -f -
export interpreter_webhook_example_service_external_ip_address=$(kubectl config view --template='{{range $_, $value := .clusters }}{{if eq $value.name "karmada-apiserver"}}{{$value.cluster.server}}{{end}}{{end}}' | \
awk -F/ '{print $3}' | \
sed 's/:.*//' | \
awk -F. '{printf "%s.%s.%s.8",$1,$2,$3}')
cat <<EOF | kubectl --context="karmada-host" apply -f -
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
name: metallb-config
namespace: metallb-system
spec:
addresses:
- ${interpreter_webhook_example_service_external_ip_address}-${interpreter_webhook_example_service_external_ip_address}
---
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
name: metallb-advertisement
namespace: metallb-system
EOF
```
### Deploy karmada-interpreter-webhook-example
#### Step1: Install `Workload` CRD
Install `Workload` CRD in `karmada-apiserver` by running the following command:
```bash
kubectl --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver apply -f examples/customresourceinterpreter/apis/workload.example.io_workloads.yaml
```
And then, create a `ClusterPropagationPolicy` resource object to propagate `Workload` CRD to all member clusters:
<details>
<summary>workload-crd-cpp.yaml</summary>
```yaml
apiVersion: policy.karmada.io/v1alpha1
kind: ClusterPropagationPolicy
metadata:
name: workload-crd-cpp
spec:
resourceSelectors:
- apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
name: workloads.workload.example.io
placement:
clusterAffinity:
clusterNames:
- member1
- member2
- member3
```
</details>
```bash
kubectl --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver apply -f workload-crd-cpp.yaml
```
#### Step2: Deploy webhook configuration in `karmada-apiserver`
We can tell Karmada how to access the resource interpreter webhook service by configuring `ResourceInterpreterWebhookConfiguration`. The configuration template is as follows:
```yaml
apiVersion: config.karmada.io/v1alpha1
kind: ResourceInterpreterWebhookConfiguration
metadata:
name: examples
webhooks:
- name: workloads.example.com
rules:
- operations: [ "InterpretReplica","ReviseReplica","Retain","AggregateStatus", "InterpretHealth", "InterpretStatus", "InterpretDependency" ]
apiGroups: [ "workload.example.io" ]
apiVersions: [ "v1alpha1" ]
kinds: [ "Workload" ]
clientConfig:
url: https://{{karmada-interpreter-webhook-example-svc-address}}:443/interpreter-workload
caBundle: {{caBundle}}
interpreterContextVersions: [ "v1alpha1" ]
timeoutSeconds: 3
```
If you only need to access the resource interpreter webhook service in the `Karmada-host` cluster, you can directly configure `clientConfig` with the Service domain name in the cluster:
```yaml
clientConfig:
url: https://karmada-interpreter-webhook-example.karmada-system.svc:443/interpreter-workload
caBundle: {{caBundle}}
```
Alternatively, you can also declare service in clientConfig:
```yaml
clientConfig:
caBundle: {{caBundle}}
service:
namespace: karmada-system
name: karmada-interpreter-webhook-example
port: 443
path: /interpreter-workload
```
You can deploy a `ExternalName` type Service in `karmada-apiserver`:
```yaml
apiVersion: v1
kind: Service
metadata:
name: karmada-interpreter-webhook-example
namespace: karmada-system
spec:
type: ExternalName
externalName: karmada-interpreter-webhook-example.karmada-system.svc.cluster.local
```
Or you do not need to deploy any Service in `karmada-apiserver`, it will fall back to standard Kubernetes service DNS name format: `https://karmada-interpreter-webhook-example.karmada-system.svc:443/interpreter-workload`.
In the example of this article, you can directly run the following script to deploy ResourceInterpreterWebhookConfiguration:
<details>
<summary>webhook-configuration.sh</summary>
```bash
#!/usr/bin/env bash
export ca_string=$(cat ${HOME}/.karmada/ca.crt | base64 | tr "\n" " "|sed s/[[:space:]]//g)
export temp_path=$(mktemp -d)
export interpreter_webhook_example_service_external_ip_address=$(kubectl config view --template='{{range $_, $value := .clusters }}{{if eq $value.name "karmada-apiserver"}}{{$value.cluster.server}}{{end}}{{end}}' | \
awk -F/ '{print $3}' | \
sed 's/:.*//' | \
awk -F. '{printf "%s.%s.%s.8",$1,$2,$3}')
cp -rf "examples/customresourceinterpreter/webhook-configuration.yaml" "${temp_path}/temp.yaml"
sed -i'' -e "s/{{caBundle}}/${ca_string}/g" -e "s/{{karmada-interpreter-webhook-example-svc-address}}/${interpreter_webhook_example_service_external_ip_address}/g" "${temp_path}/temp.yaml"
kubectl --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver apply -f "${temp_path}/temp.yaml"
rm -rf "${temp_path}"
```
</details>
```bash
chmod +x webhook-configuration.sh
./webhook-configuration.sh
```
#### Step3: Deploy `karmada-interpreter-webhook-example` in karmada-host
Run the following command:
```bash
kubectl --kubeconfig $HOME/.kube/karmada.config --context karmada-host apply -f examples/customresourceinterpreter/karmada-interpreter-webhook-example.yaml
```
> Note: `karmada-interpreter-webhook-example` is just a demo for testing and reference. If you plan to use the interpreter webhook, please implement specific components based on your business needs.
In the current example, the interpreter webhook is deployed under the namespace `karmada-system`. If you are trying to deploy the interpreter webhook in a namespace other than the default karmada-system namespace, and use the domain address of Service in the URL. Such as (take the `test` namespace as an example):
```yaml
apiVersion: config.karmada.io/v1alpha1
kind: ResourceInterpreterWebhookConfiguration
metadata:
name: examples
webhooks:
- name: workloads.example.com
rules:
- operations: [ "InterpretReplica","ReviseReplica","Retain","AggregateStatus", "InterpretHealth", "InterpretStatus", "InterpretDependency" ]
apiGroups: [ "workload.example.io" ]
apiVersions: [ "v1alpha1" ]
kinds: [ "Workload" ]
clientConfig:
url: https://karmada-interpreter-webhook-example.test.svc.cluster.local:443/interpreter-workload # domain address here
caBundle: {{caBundle}}
interpreterContextVersions: [ "v1alpha1" ]
timeoutSeconds: 3
```
Please set the correct certificate and add the domain address to the CN field of the certificate.
In the testing environment of Karmada, this is controlled in script `hack/deploy-karmada.sh`:
https://github.com/karmada-io/karmada/blob/303f2cd24bf5d750c2391bb6699ac89d78b3c43f/hack/deploy-karmada.sh#L155
We recommend that you deploy the interpreter webhook component and Karmada control plane components in the same namespace. If you need to deploy them in different namespaces, please plan ahead when generating certificates.
The relevant problem description has been recorded in [#4478](https://github.com/karmada-io/karmada/issues/4478), please refer to it.
At this point, you have successfully installed the `karmada-interpreter-webhook-example` service and can start using it.
### Usage
Create a `Workload` resource and propagate it to the member clusters:
<details>
<summary>workload-interpret-test.yaml</summary>
```yaml
apiVersion: workload.example.io/v1alpha1
kind: Workload
metadata:
name: nginx
labels:
app: nginx
spec:
replicas: 3
paused: false
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
---
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: nginx-workload-propagation
spec:
resourceSelectors:
- apiVersion: workload.example.io/v1alpha1
kind: Workload
name: nginx
placement:
clusterAffinity:
clusterNames:
- member1
- member2
- member3
replicaScheduling:
replicaDivisionPreference: Weighted
replicaSchedulingType: Divided
weightPreference:
staticWeightList:
- targetCluster:
clusterNames:
- member1
weight: 1
- targetCluster:
clusterNames:
- member2
weight: 1
- targetCluster:
clusterNames:
- member3
weight: 1
```
</details>
```bash
kubectl --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver apply -f workload-interpret-test.yaml
```
#### InterpretReplica
You can get `ResourceBinding` to check if the `replicas` field is interpreted successfully.
```bash
kubectl get rb nginx-workload -o yaml
```
#### ReviseReplica
You can check if the replicas field of `Workload` object is revised to 1 in all member clusters.
```bash
kubectl --kubeconfig $HOME/.kube/members.config --context member1 get workload nginx --template={{.spec.replicas}}
```
#### Retain
Update `spec.paused` of `Workload` object in member1 cluster to `true`.
```bash
kubectl --kubeconfig $HOME/.kube/members.config --context member1 patch workload nginx --type='json' -p='[{"op": "replace", "path": "/spec/paused", "value":true}]'
```
Check if it is retained successfully.
```bash
kubectl --kubeconfig $HOME/.kube/members.config --context member1 get workload nginx --template={{.spec.paused}}
```
#### InterpretStatus
There is no `Workload` controller deployed on member clusters, so in order to simulate the `Workload` CR handling,
we will manually update `status.readyReplicas` of `Workload` object in member1 cluster to 1.
```bash
kubectl proxy --port=8001 &
curl http://127.0.0.1:8001/apis/workload.example.io/v1alpha1/namespaces/default/workloads/nginx/status -XPATCH -d'{"status":{"readyReplicas": 1}}' -H "Content-Type: application/merge-patch+json
```
Then you can get `ResourceBinding` to check if the `status.aggregatedStatus[x].status` field is interpreted successfully.
```bash
kubectl get rb nginx-workload --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver -o yaml
```
You can also check the `status.manifestStatuses[x].status` field of Karmada `Work` object in namespace karmada-es-member1.
#### InterpretHealth
You can get `ResourceBinding` to check if the `status.aggregatedStatus[x].health` field is interpreted successfully.
```bash
kubectl get rb nginx-workload --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver -o yaml
```
You can also check the `status.manifestStatuses[x].health` field of Karmada `Work` object in namespace karmada-es-member1.
#### AggregateStatus
You can check if the `status` field of `Workload` object is aggregated correctly.
```bash
kubectl get workload nginx --kubeconfig $HOME/.kube/karmada.config --context karmada-apiserver -o yaml
```
> Note: If you want to use `Retain`/`InterpretStatus`/`InterpretHealth` function in Pull mode cluster, you need to deploy karmada-interpreter-webhook-example in the Pull mode cluster.
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