Container Service for Kubernetes:Reuse an existing SLB instance to expose Services in different ACK clusters

Scenario 1: Distribute traffic to a Service in the cluster and an endpoint outside the cluster

To do this, you can mount a Service in the cluster and an endpoint outside the cluster, such as an Elastic Compute Service (ECS) instance, to the same SLB instance.

1. Log on to the CLB console or NLB console and view the ID of an existing SLB instance.

2. Select the SLB instance when you create a Service.

   Use the console

   When you create a Service in the ACK console, set Service Type to Server Load Balancer and select Use Existing SLB Instance. Then, select the SLB instance from the drop-down list and select Overwrite Existing Listeners.

   Use kubectl

   When you use kubectl to create a Service, add an annotation to specify the ID of the SLB instance.

   apiVersion: v1
   kind: Service
   metadata:
     annotations:
       service.beta.kubernetes.io/alibaba-cloud-loadbalancer-id: ${LB_ID} # Replace ${LB_ID} with the ID of the SLB instance. 
       service.beta.kubernetes.io/alibaba-cloud-loadbalancer-force-override-listeners: "true"  # Set the value to true to automatically create listeners and vServer groups. 
     labels:
       #...
     name: #...
   spec:
     #...

   Important

   After the Service is created, cloud-controller-manager creates a vServer group and a listener that is associated with the vServer group and listens on the Service port for the SLB instance.

3. Log on to the CLB console or NLB console. Add an endpoint outside the cluster to the vServer group. For more information, see Create and manage a CLB vServer group and Create and manage a vServer group.

   After you complete the configuration, you can find pods and the external endpoint in the vServer group and set their weights. When a scaling activity is triggered, pods are automatically added to or removed from the vServer group. Scaling activities do not affect the external endpoint.

Scenario 2: Distribute traffic to Services in different ACK clusters

You can mount Services in different ACK clusters to the same SLB instance. The SLB instance serves as a unified ingress.

To automatically update the endpoints of the SLB instance when the backend pods of the Services are changed, you must configure the Services to use the same listener and vServer group of the SLB instance. To do this, you need to manually create a listener and vServer group for the SLB instance, and configure the Services to reuse the vServer group and the listener to listen on the Service port.

1. Log on to the CLB console or NLB console and create a listener and vServer group for the SLB instance. For more information, see CLB listener overview, Create and manage a CLB vServer group, Overview of NLB listeners, and Create and manage a server group.

2. When you create Services, reuse the vServer group that you manually created.

   To do this, add annotations to the Services to specify the IDs of the SLB instance and vServer group. You can also set the weights of the Services.

   apiVersion: v1
   kind: Service
   metadata:
     annotations:
       service.beta.kubernetes.io/alibaba-cloud-loadbalancer-id: "${YOUR_LB_ID}" # Replace ${YOUR_LB_ID} with the ID of the SLB instance. 
       service.beta.kubernetes.io/alibaba-cloud-loadbalancer-vgroup-port: "${YOUR_VGROUP_ID}:{PORT}" # Replace ${YOUR_VGROUP_ID} with the ID of the vServer group and {PORT} with the port of the Service. 
       service.beta.kubernetes.io/alibaba-cloud-loadbalancer-weight: "100" # This annotation is optional. This annotation specifies the weights of the backend pods of the Service. Valid values: 1 to 1000. Default value: 100. 
     labels:
       #...
     name: #...
   spec:
     #...

   Note

   If you want to set service.beta.kubernetes.io/alibaba-cloud-loadbalancer-vgroup-port to multiple port-to-vServer group mappings, separate the mappings with commas (,). Example: "${YOUR_VGROUP_ID_1}:80, ${YOUR_VGROUP_ID_2}:443".

   After you complete the configuration, you can find the pods of the Services in the vServer group in the SLB console. If an application is scaled, pods are automatically added to or removed from the vServer group for the application. Pods that belong to other applications are not affected.

   Important

   If you have set the weights of the Services by adding the corresponding annotation, do not modify the weights in the console because the changes cannot be synchronized to the Services.

References

• For more information about annotations, see Use annotations to configure CLB instances and Use annotations to configure NLB instances.

• For more information about the release notes for the cloud-controller-manager component, see Cloud Controller Manager.