前提

用户能够通过多集群服务API在集群之间导出和导入服务。

注意：使用该特性需要满足成员集群的kubernetes版本在v1.21以上（包含v1.21）。

• 安装karmada
  
• 成员集群网络
  确保至少有两个集群被添加到 Karmada，并且成员集群之间的容器网络可相互连接。这里已经使用了Submariner Globalnet模式打通了集群间网络。
• 安装 ServiceExport 和 ServiceImport CRD
  创建 ClusterPropagationPolicy 来分发这两个 CRD 到成员集群。

  # propagate ServiceExport CRD
  apiVersion: policy.karmada.io/v1alpha1
  kind: ClusterPropagationPolicy
  metadata:
  name: serviceexport-policy
  spec:
  resourceSelectors:
  - apiVersion: apiextensions.k8s.io/v1
    kind: CustomResourceDefinition
    name: serviceexports.multicluster.x-k8s.io
  placement:
  clusterAffinity:
    clusterNames:
      - member1
      - member2
      - member3
  ---        
  # propagate ServiceImport CRD
  apiVersion: policy.karmada.io/v1alpha1
  kind: ClusterPropagationPolicy
  metadata:
  name: serviceimport-policy
  spec:
  resourceSelectors:
  - apiVersion: apiextensions.k8s.io/v1
    kind: CustomResourceDefinition
    name: serviceimports.multicluster.x-k8s.io
  placement:
  clusterAffinity:
    clusterNames:
      - member1
      - member2
      - member3

  

步骤

在member1集群上部署服务

apiVersion: apps/v1
kind: Deployment
metadata:
  name: serve
spec:
  replicas: 1
  selector:
    matchLabels:
      app: serve
  template:
    metadata:
      labels:
        app: serve
    spec:
      containers:
      - name: serve
        image: jeremyot/serve:0a40de8
        args:
        - "--message='hello from cluster member1 (Node: {{env \"NODE_NAME\"}} Pod: {{env \"POD_NAME\"}} Address: {{addr}})'"
        env:
          - name: NODE_NAME
            valueFrom:
              fieldRef:
                fieldPath: spec.nodeName
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
---      
apiVersion: v1
kind: Service
metadata:
  name: serve
spec:
  ports:
  - port: 80
    targetPort: 8080
  selector:
    app: serve
---
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
  name: mcs-workload
spec:
  resourceSelectors:
    - apiVersion: apps/v1
      kind: Deployment
      name: serve
    - apiVersion: v1
      kind: Service
      name: serve
  placement:
    clusterAffinity:
      clusterNames:
        - member1

导出服务到 member2 集群

在karmada控制平面上创建一个 ServiceExport 对象，然后创建一个 PropagationPolicy ，将 ServiceExport 对象分发到 member1 集群。

apiVersion: multicluster.x-k8s.io/v1alpha1
kind: ServiceExport
metadata:
  name: serve
---
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
  name: serve-export-policy
spec:
  resourceSelectors:
    - apiVersion: multicluster.x-k8s.io/v1alpha1
      kind: ServiceExport
      name: serve
  placement:
    clusterAffinity:
      clusterNames:
        - member1

在karmada控制平面上创建一个 ServiceImport 对象，然后创建一个 PropagationPlicy 来分发 ServiceImport 对象到 member2 集群。

apiVersion: multicluster.x-k8s.io/v1alpha1
kind: ServiceImport
metadata:
  name: serve
spec:
  type: ClusterSetIP
  ports:
  - port: 80
    protocol: TCP
---
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
  name: serve-import-policy
spec:
  resourceSelectors:
    - apiVersion: multicluster.x-k8s.io/v1alpha1
      kind: ServiceImport
      name: serve
  placement:
    clusterAffinity:
      clusterNames:
        - member2

vim svcimport.yaml
vim svcexport.yaml
ka get serviceimport
ka get serviceexport
ka get propagationpolicy
ka get svc

从 member2 集群获取服务

经过上述步骤，我们可以在 member2 集群上找到前缀为 derived- 的派生服务。然后，我们可以访问派生服务来访问member1集群上的服务。

member3上没有，因为没有导入到member3中。

使用服务derived-serve的 CLUSTER-IP 10.110.165.85持续访问该服务3s。

k --kubeconfig kubeconfig.member2 run -i --rm --restart=Never --image=jeremyot/request:0a40de8 request -- --duration=3s --address=10.110.165.85

注意

这里不能用上面的方法测试，会无法连接。因为我这个环境已经使用了external-webhook，所以需要使用globalingressips来替代CLUSTER-IP。

k get globalingressips.submariner.io
k --kubeconfig kubeconfig.member2 run -i --rm --restart=Never --image=jeremyot/request:0a40de8 request -- --duration=3s --address=242.0.255.252

实现了跨集群服务访问。