Balance to Services Running across Child Clusters

How to visit services running across child clusters

For services in child clusters, we can use service name to visit them locally from parent cluster.

Note

Make sure parent cluster can visit child clusters pod CIDR and each cluster must use distinct pod CIDRs that don’t conflict or overlap with any other cluster.
Make sure experimental feature MultiClusterService is enabled both on clusternet-agent and clusternet-controler-manager side. You can manually enable the feature by directly modifying with --feature-gates=xxx,MultiClusterService=true of deployments clusternet-controller-manager and clusternet-agent.

1. Deploying applications to multiple clusters with various scheduling strategies

Please follow this example. to deploy applications to multiple clusters.

$ kubectl clusternet apply -f examples/scheduling-with-mcs-api/scheduling
namespace/baz created
deployment.apps/my-nginx created
service/my-nginx-svc created
serviceexport.multicluster.x-k8s.io/my-nginx-svc created
subscription.apps.clusternet.io/scheduling-with-mcs-api created

2. Deploying serviceimport in parent cluster

Deploy serviceimport in parent cluster, specify which service you want to import in labels:

apiVersion: multicluster.x-k8s.io/v1alpha1
kind: ServiceImport
metadata:
  name: my-svc
  namespace: default
  labels:
    services.clusternet.io/multi-cluster-service-name: my-nginx-svc # must be same to the service name you want to expose
    services.clusternet.io/multi-cluster-service-namespace: baz # must be same to the service namespace
spec:
  ips:
    - 42.42.42.42
  type: "ClusterSetIP"
  ports:
  - port: 80
    protocol: TCP
  sessionAffinity: None

$ kubectl create -f examples/scheduling-with-mcs-api/service-import.yaml
serviceimport.multicluster.x-k8s.io/my-svc created

3. Check service and endpointslice.

Now we can check and verify the endpointslice and service auto derived by clusternet the service start with derived-:

root@worker-cluster1-1:~/clusternet# kubectl get svc 
NAME                     TYPE           CLUSTER-IP      EXTERNAL-IP    PORT(S)        AGE
derived-baz-tc8hmv632j   ClusterIP      10.11.178.229   <none>         80/TCP         1d
kubernetes               ClusterIP      10.11.0.1       <none>         443/TCP        306d
root@worker-cluster1-1:~/clusternet# kubectl get svc derived-baz-tc8hmv632j -o yaml
apiVersion: v1
kind: Service
metadata:
  creationTimestamp: "2022-09-01T07:42:31Z"
  name: derived-baz-tc8hmv632j
  namespace: default
  resourceVersion: "100369299"
  selfLink: /api/v1/namespaces/default/services/derived-baz-tc8hmv632j
  uid: 91c19b02-c15b-4166-9bcc-6931d0859723
spec:
  clusterIP: 10.11.178.229
  clusterIPs:
  - 10.11.178.229
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer:
    ingress:
    - ip: 42.42.42.42

And the endpointslice with label kubernetes.io/service-name: derived-baz-tc8hmv632j :

$ kubectl get endpointslice -l kubernetes.io/service-name=derived-baz-tc8hmv632j
NAME                                      ADDRESSTYPE   PORTS   ENDPOINTS                                         AGE
clusternet-s5cmf-baz-my-nginx-svc-4rg6x   IPv4          80      10.244.1.36,10.244.1.40,10.244.1.38 + 3 more...   10m

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Last modified May 15, 2023: add mcs featuregate description (#84) (b501ad2)